Note: Descriptions are shown in the official language in which they were submitted.
POLYMER BATTERIES AND FUEL CELLS HAVING_PROTIC SOLVENTS
AND MET~ODfi FOR THEIR CONSTRUCTION END USE
Certain aspects of the invention described herein were made
during the course of York performed under grants or awards from
the Office of Naval Research and from the Defense Advanced
Research Project Agency through a grant monitored by the Office
of Naval Research.
FIELD OF THE INVENTION
This invention relates to electr~chemical doping procedures
or the selective modification of the electrical conductivity
properties of certain conjugated polymers, and to the
application of such procedures to the design of novel,
lightweight, high energy density and high power density
secondary (reversible) batteries. This invention is also
directed to fuel cells wherein simultaneous electrochemical
reduction of electrochemically reducible species and
electrochemical oxidation of electrochemically oxidizable
species takes place at different electrodes, with concomitant
generation of electric current together with methods for such
generation. Reverse reactions, electrolysis, are also
contemplated hereby All of the foregoing embodiments of this
invention employ conjugated polymers having conjugated
unsaturation along a main backbone chain thereof as either or
both of anodic and cathodic means in electrolytic cells,
batteries and/or fuel cells. Electrolytes are also employed in
connection with the embodiments of this invention, which
electrolytes comprise solvents which are erotic in nature, that
is, which are able to donate protons readily. Examples of such
solvents include water, alcohols, amine, and other solvents
well known to those skilled in the art.
BACKGROUND OF THE INVENTION
It has recently been found that acetylene polymers, such as
polyacetylene, can be chemically doped in a controlled manner
I
-- 2 --
with electron acceptor and/or electron donor do pants to produce a
whole family of p-type and n-type electrically conducting doped
acetylene polymers whose room temperature electrical conductivity
may be preselected over the entire range characteristic of semi-
conductor behavior and into the range characteristic of metallic
behavior. Such doping procedures and the resulting doped
acetylene polymers are described and claimed in the commonly
assigned U.S. Patent No. 4,222,903, of Alan J. Hedger, Alan J.
MacDiarmid, Cowan K. Shying, and Haddock Cherokee, issued
September 16, 1980; and in the commonly assigned U.S. Patent
No. 4,204,216, of Alan J. Hedger, Alan G. MacDiarmid, Cowan K.
Shying, and Shucking Gaul issued May 20~ 1980. As described in
said Fleeter, et at. patents, a p-type material is obtained with
electron acceptor do pants, and an n-type material is obtained
with electron donor do pants. The resulting room temperature elect
tribal conductivity of the doped acetylene polymer increases with
increasing degree of doping up to a certain point where the maxim
mum conductivity is obtained or any given Dupont. Such maximum
conductivity generally is obtained at a degree ox doping not
greater than about 0.30 mole of Dupont per -OH- unit of polyp
acetylene.
The doping procedures described in said edgier, et at.
patents involve merely contacting the acetylene polymer with the
Dupont, which may be either in the vapor phase or in an aprotic
solvent; uptake of the Dupont into the acetylene polymer occurs
by chemical reaction and/or charge transfer to a degree proper-
tonal with both the Dupont concentration and the contacting
period. The concentration and contacting period can be co-
ordinate and controlled so that the corresponding degree of
doping will be such as to provide the resulting doped acetylene
polymer with a preselected room temperature conductivity.
Doped acetylene polymers together with other polymers
having conjugated unsaturation in a backbone chain thereof con-
statute one class of recently developed molecular solids
exhibiting relatively high levels ox electrical conductivity.
. . .
~,.,,;~
'$
I
Several other molecular solids have previously been
investigated as electrode materials in attempts at improved
battery design. For example, U. S. Patent Jo. 3,660,163 issued
May 2, 1972 to Moser; and Schneider, et Allah Pro. Into Power
sources Con., 651-659 (1974), describe the use of a charge
transfer complex of poly-2-vinylpyridine with excess iodine as
a cathode material in a solid-state lithium-iodide primary
battery employing lithium iodide as a solid electrolyte.
A recent article by Yoshimura, appearing in Molecular
Metals, William E. Hatfield, Ed., NOAH Conference Series,
Series VI: Materials Science, pp. 471-489 (197~), at pages
~74-476, refers to the above described prior art solid-state
lithium-iodine primary battery constructed with
poly-2-vinylpyridine-iodine charge transfer complex cathode
materials, and broadly speculates that a number of the
molecular metals, including doped polyacetylene, might possibly
find similar utility as cathode materials in battery design.
No details are provided in regard to the possible construction
or mode of operation of such hypothetical batteries, however.
Furthermore, the possibility of doped acetylene or other
conjugated polymers being employed as anode materials or as one
or both of the electrode materials in a secondary battery
construction, i.e., in batteries which are capable of being
charged and discharged over many cycles, is not suggested in
this article.
In the aforementioned Moser US S. Patent No. 3,660,163, a
number of organic donor components in addition to
polyvinylpyridine are listed as being suitable for forming the
iodine charge transfer complex cathode material. The only one
of these many materials listed in the patent which happens to
be a conjugated polymer is polypyrrole. Moser attaches no
particular significance to polypyrrole, either as being a
conjugated polymer or as having any unique electrochemical
properties in either its uncompleted or iodine-complexed form,
which might set it apart from the many other organic donor
components listed therein. There is no appreciation in the
Moser patent that doped polypyrrole, or any other doped
~;23~
conjugated polymer, could be used as one or both of the electrode
materials in a secondary battery construction.
Polymers such as polyacetylene and polyphenylenes have
been disclosed to be reversibly, electrochemically dupable by a
variety of Dupont species in aprotic solvents. Further, second
defy, reversible batteries are also disclosed as being able to be
constructed from such materials. Secondary batteries are disk
closed as being constructed from conjugated polymers having coinage-
grated unsaturation along a main backbone chain thereof, said
polymer being electrochemically reducible to an n-type doped
material and electrochemically oxidizable to a type doped
material in non-aqueous electrolytes comprising a compound which
is ionizable into one or more anionic or cat ionic Dupont species
capable of doping the polymer to one of the oxidized or reduced
states.
British Patent 1,216,549 - Josefowicz, together with
French Patent 1,519,729, Jozefowicz, and "Conductivity of High
Polymer Compounds in Solid State", Josefowicz, East Ion Transport
in Solids - Solid State batteries and Devices, Proceedings of a
NATO sponsored Advanced Study Institute, Belgirate, Italy,
pp. 623-63S (1973) r discloses the electrochemical doping of
certain polymers, especially polyaniline, in erotic media, however
the polymers disclosed are not electrochemically dupable to both p
and n states.
None of the foregoing are believed to anticipate or
render obvious, either alone or in combination, this novel invent
lion as reflected by the claims.
.
Jo
-- 5 --
SUMMARY OF THE INVENTION
-
It is an object of this invention to provide secondary
batteries having one or more electrodes comprising a conjugated
polymer having conjugated unsaturation along a main backbone
chain thereof, said polymer being electrochemically oxidizable
to a p-type doped material and electrochemically reducible to
an n-type doped material, and an electrolyte comprising a
erotic solvent together with at least one ionic Dupont capable
of doping the polymer to a conductive state in the electrolyte.
Another object is to provide secondary batteries having
aqueous, alcoholic, or ammonia Cal electrolytes.
A further object is to provide secondary batteries
comprising polyacetylene or polyphenylene electrode materials
and erotic electrolytes.
Another object is to provide chemical methods for doping
certain conjugated polymers.
Secondary batteries wherein erotic solvent-based
electrolytes are employed which are capable of doping
conjugated polymers comprising one or more electrodes of the
battery to a conductive state are also contemplated hereby.
Electrochemical methods for modifying the electrical
conductivity of organic polymers are also principal objects of
this invention.
It is a further object to provide methods for reversibly
doping certain conjugated polymers in erotic solvents,
especially aqueous solvents.
It is yet another object of the present invention to
provide electrochemical fuel cells capable of simultaneously
oxidizing an oxidizable species and reducing a reducible
species at different electrodes with the concomitant generation
of electric current.
Another object of this invention is to provide
electrochemical fuel cells employing certain conjugated
polymers which are dupable with Dupont species to a conducting
state for the catalytic oxidation-reduction of suitable
oxidizable and reducible species.
1234~
-6- 3189-271
Yet another object of this invention is to provide
methods for the electrochemi~cal generation of electric current
through the conjugated polymer-catalyzed oxidation-reduction of
suitable oxidizable and reducible species in erotic, especially
aqueous, media.
A further object of the invention provides electrolysis
of chemical species into their constituent elements or compounds
by the application of current to suitable electrochemical cells
employing conjugated polymers as catalyst electrodes.
Yet another object is to provide methods for electrode-
fining of metals.
Further objects will be apparent to those of ordinary
skill in the art from a review of the present specification, to-
getter with those materials referenced above.
The foregoing objects and other objects are achieved
through the employment of certain conjugated polymers in erotic
electrolytic media. Similarly, certain electrochemical doping pro-
seeders are employed in order to facilitate attainment of the fore-
going objects. Secondary batteries may be produced having good
reversibility, life times, power densities, energy densities, and
overall coulombic efficiency comprising an anode, a cathode, and an
electrolyte. One or both of the anode and cathode comprises a con-
jugated polymer having conjugated unsaturation along a main back-
bone chain thereof, said polymer being electrochemically oxidizable
to a p-type doped material and electrochemically reducible to an
n-type doped material. The electrolyte comprises a erotic solvent
and at least one ionic Dupont capable of doping the polymer -to a
conductive state in the electrolyte. The foregoing secondary
-pa- 3189-271
battery may be "charged" by passing current through the cell to
effect doping of the conjugate polymer to a more highly conducting
state in a reversible fashion. Reversing this process -discharge-
provides electric current and returns the polymer to a less highly
doped state.
In accordance with the present invention, an electron
chemical fuel cell may-be provided comprising an
I
electrolyte, electrochemically oxidizable fuel, an electrochemically reducible
oxidizing agent and catalyst electrode means in contact with the electrolyte
comprising a conjugated polymer having conjugated unsaturation along a main
backbone chain thereof, said polymer being electrochemically oxidizable to a
p-type doped material and electrochemically reducible to an n-type doped
material. The electrolyte comprises a erotic solvent, and at least one ionic
Dupont capable of doping the polymer to a conducting state in the electrode.
Second electrode means in contact with the electrolyte is also provided for
current collection and other purposes. The foregoing electrochemical fuel cell
may be employed for the electrochemical generation of electric current by
withdrawing current from the fuel cell to effect at least a partial electron
chemical oxidation of the fuel and at least a partial electrochemical reduction
of the oxidizing agent. The foregoing fuel cell may likely also be operated in
"reverse' as an electrolysis cell. Thus, an electrical over-potential may be
applied to the catalyst and second electrodes of the electrochemical fuel cell
as described to cause electrolysis of the oxidized and reduced materials back into
their oxidizable and reducible forms. In accordance with a preferred embodiment
one or both of the fuel and oxidizing agents is a gas.
An aspect of the present invention provides an electrochemical cell
comprising first and second electrodes, at least one of said electrodes
comprising a conjugated polymer having conjugated unsaturation along a main
backbone chain thereof, said polymer being electrochemically oxizable to a p-type
doped material and electrochemically reducible to an n-type doped material, and
an electrolyte, said electrolyte comprising a erotic solvent and at least one
ionic Dupont capable of doping said polymer to a conductive state in said
electrolyte.
- pa -
One embodiment of the first aspect of the invention provides a
secondary battery comprising an anode; a cathode comprising a conjugated polymer
having conjugated unsaturation along a main backbone chain thereon, said
polymer being electrochemically oxidizable to a p-type doped material and
electrochemically reducible to an n-type doped material; and an electrolyte,
said electrolyte comprising a erotic solvent and at least one ionic Dupont
capable of doping said polymer to a conductive state in said electrolyte.
Another embodiment of the first aspect of the invention provides
a secondary battery comprising a cathode; an anode comprising a conjugated
polymer having conjugated unsaturation along a main backbone chain thereof,
said polymer being electrochemically oxidizable to a p-type doped material and
electrochemicaLly reducible to an n-type doped material; and an electrolyte,
said electrolyte comprising a erotic solvent and at least one ionic Dupont capable
of doping said polymer to a conductive state in said electrolyte.
Still another embodiment of the first aspect of the invention provides
a secondary battery comprising an anode; a cathode; and an electrolyte; said
anode and cathode each comprising a conjugated polymer having conjugated
unsaturation along a main backbone chain thereof, said polymer being electron
chemically oxidizable to a p-type doped material and electrochemically reducible to
an n-type doped material; said electrolyte comprising a erotic solvent and at
least one Dupont capable of doping said polymer to a conductive state in said
electrolyte; the cathode polymer being electrochemically p-doped with said Dupont
to an oxidized state as compared with the anode polymer.
A further embodiment of the first aspect of the invention provides
an electrochemical fuel cell comprising: an electrochemically oxidizable fuel;
cm electrochemically reducible oxidizing agent; catalyst electrode means
I
- 7b -
comprising a conjugated polymer having conjugated unsaturation along a main
backbone chain thereof, said polymer being electrochemically oxidizable to a
p-type doped material and electrochemically reducible to an n-type doped
material; an electrolyte in contact with said catalyst electrode comprising
a erotic solvent, and at least one ionic Dupont capable of doping said polymer
to a conductive state in the electrolyte; and second electrode means in contact
with the electrolyte.
The second aspect of the invention provides an electrochemical method
for modifying the electrical conductivity of an organic polymer comprising
providing an electrochemical cell comprising an anode; a cathode, at least one
of said electrodes comprising a conjugated polymer having conjugated
maturation along a main backbone chain thereof, said polymer being
el.ectrochemically oxidizable to a p-type doped material and electrochemically
reducible to an n-type doped material; and an electrolyte comprising a erotic
solvent and at least one ironic Dupont capable of doping the polymer to a
conductive state in said electrolyte; and passing current through the cell -to
effect said doping of the polymer to a more highly conducting state, said
doping being substantially reversible.
The third aspect of the invention provides a method for the electron
chemical generation of electric current comprising providing an electrochemicalcell comprising an electrochemically oxidizable fuel; an electrochemically
reducible oxidizing agent; an electrolyte; catalyst electrode means in contact
with the electrolyte comprising a conjugated polymer having conjugated
unsatu:ration along a main backbone chain Thor, said polymer being electron
chemically oxidizable to a p-type doped material and electrochemically reducible
to all n-type doped material; said electrolyte comprising a erotic solvent, and
I
- 7c -
an ionic Dupont capable of doping said polymer to a conducting state in the
electrolyte; and second electrode means in contact with the electrolyte; and
operating the cell to effect at least a partial electrochemical oxidation
of said fuel and at least a partial electrochemical reduction of said oxidizing
agent .
BRIE DESCRIPTION OF TIRE DRAWINGS
Figures 1 through 4 depict the spontaneous chemical doping of
polyacetylene in aqueous acid solutions in accordance with certain of the
Examples.
DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS
As used herein, the term "Dupont" or "ionic Dupont" for a
polymer refers to an ionic species which is capable of associating
with the polymer to permit substantial addition or withdrawal of electric
charge to/from the polymer and to permit modification of the electrical
conductivity owe the polymer. The Dupont, as used herein, therefore may be
viewed as an ionic species which provides the counter ionic presence in
a polymer
I
-- 8 --
necessary for the establishment of conductive properties
therein. As will be readily appreciated by those skilled in
the art, ionic do pants are generally associated with moieties
having opposite electrical charge, ire. in compounds,
especially as dissociable salts.
In the case of chemical doping of a polymer, the electrical
modification of the polymer, i.e. the addition or withdrawal of
electrons, is accomplished by contacting the polymer with a
chemical species capable of participating in an
oxidation-reduction, i.e. redo, reaction with the polymer. In
such a case, the redox-participating species may or may not
also be the source of Dupont ions for maintaining electrical
neutrality in the polymer. In the case where a single chemical
species performs both functions, it is possible to confuse the
roles. A species which is a Dupont in accordance with the
present definition will experience no change in its oxidation
state upon doping. A species which participates in a redo
reaction will, of course, experience an alteration in
oxidization state on account of that participation. Different
molecules of the same, original species or, indeed, the same
molecules may perform both functions, i.e. serve as redo
participant and as Dupont ion The Dupont ion must not,
however, react irreversibly with the oxidized or reduced
polymer.
As used herein, the phrase "capable of doping" as applied
to a Dupont or Dupont ion refers to the ability of the Dupont
to associate with the material being doped, e.g. the polymer,
to permit the addition or withdrawal of charge and the
concomitant modification of conductivity in the material by
ensuring electrical neutrality.
As used herein, a "conductive state" as applied to a
material such as a polymer, refers to a state of the material
in which electrical conductivity as measured in ohm cm
is substantially increased over the native state of the
material such as, for example, by several orders of magnitude.
Whose skilled in the art will appreciate that a practical
definition of "conductive state" may vary depending upon the
I
g
proposed application of the material under consideration and
that it will include both semi conducting and metallic regimes
Useful "conductive states" may include states having
conductivities above about 10 ohm cm . For common
battery uses, conductivities above about 1 ohm tam 1 are
most desired.
As used herein with respect to a secondary battery, "anode"
refers to the situp of oxidation and "cathode" refers to the
situp of reduction of the battery in the discharging mode,
i.e., in the charged battery.
In order to appreciate the unexpected nature of the
materials and processes described herein, it is desirable to be
familiar with the effects of gaseous oxygen, liquid water, and
air on the conductivity of neutral polyacetylene and p doped,
i.e. partially oxidized, polyacetylene. The effect of a
mixture of the vapors of an oxidizing acid and water on
polyacetylene should also ye understood.
Gaseous oxygen will very slightly reversibly oxidize
polyacetylene, increasing its conductivity from about
10 ohm tam 1 to about -8 -1 -1 This
oxidation is attended by an irreversible chemical reaction,
however. The 2 combines chemically with the polyacetylene
with concomitant, permanent loss of conductivity after about
five minutes of exposure. The conductivity drops to about
10 1 ohm cm after about 17 hours of exposure. See
"Kinetics of Doping and Degradation of Polyacetylene by
Oxygen", Potion et at., Macromolecules, Vol. 14, pp. 1~0 114
(1981); "Oxygen Doping of Polyacetylene", Potion et at., J.
Polymer Sat., Polymer Letters Ed., Vol. 18, pp. 447-~51 (1980);
"Effects of Oxidation on It Doping of Trans-Polyacetylene as
Studied via ESSAYER. and Conductivity Measurements", Potion et
at., Polymer, Vol. 23, pp. 439-444 (1982); "Organic Metals and
Semiconductors: The Chemistry of Polyacetylene, (SHUCKS, and
Its Derivatives", MacDiarmid et at., Synthetic Metals, Vol. 1,
pp. 101-118 (1979/80); and "Electrical Transport in Doped
Polyacetylene", Park et. at., Journal of Chemical Physics, Vol.
73, pp. 946-957 (1980). The (SHUCKS is destroyed and is
I
-- 10 --
converted to a complex, unknown mixture of compounds, all of
which contain strong adsorption peaks in the infrared spectra
characteristic of the carbonyl group, indicating oxidative
degradation.
In addition, there are many reports in literature which
stress the reduction in conductivity of c1s or trays
polyacetylene when exposed to air. See the foregoing
references along with "Stability of Polyacetylene Films", Yen
et at., Solid State Communications, Vol. I pp. 339-343
(1980); and "A Kinetic Study of the Interactions of
Trans-Polyacetylene (SHUCKS with Oxygen", Helm et at.,
yo-yo, Vol. 23, pp. 1409-1411 (1982).
There have also been many statements in the literature
pointing out the reduction in conductivity of p-doped
polyacetylene when exposed to air or oxygen. See, for example,
"Conductivity and Hall Effect Measurements in Doped
Polyacetylene", Seeker et at., Solid State Communications, Vol.
.
I pp. 873-878 (1978); "A Study of Posy (p-Xylylene) - Coated
AsF5 - Doped Polyacetylene", Osterholm et at., Journal of
Applied Polymer Science, Vol. 27, pp. 931-936 (1982); and
"Electrical Transport in Doped Polyacetylene", Park eta
Journal of Chemical Physics, Vol. 73, pp. 946-957 (19803.
It has been suggested that p-doped polyacetylene may have
at least some chemical stability in certain selected aqueous
solutions. As reported in ~igrey, MacDiarmid and Hedger, J.
Comma So., Chum. Comma., p. 594 (1979), (Shucks was
electrochemically doped in 0.5M aqueous KIT solution in a few
minutes to give (Chit 07)x having a conductivity in the
metallic regime The sum of elemental analyses for C, H, and I
was 99.8%. This showed that no reaction with water to
incorporate oxygen into the (SHUCKS had taken place. As time
proceeded, however, it was believed that the analysis must have
been in error, and that oxygen surely must have been
incorporated during the doping process. Very recently,
however, the experiment was repeated and similar results
obtained. Eons the [OH (It Jo 0415]x formed
(KIWI%) did not react with water, or, if it did react
I
-- 11 --
during its electrochemical synthesis, the rate of reaction with
water must have been very much less than its rate of formation
at least during the time needed for doping Recent studies
also show that the rate of decomposition of [Shucks in
aqueous solutions of various pi and chloride ion concentration
values is slow. See Week et at., A streets, I.V.P.A.C. Thea
Macromol. Swamp., July 12-16, 1982, p. 442.
MacDiarmid and Hedger in Comma Surety, Vol. 17, p. 143
(1981) and A. Prong Ph.D. Thesis, University of Pennsylvania,
p. ]50 (1980) have found that when a strip of (SHUCKS film
anhydrously doped to the metallic regime, having a composition
of [CH(AsF5)0 098~x~ was placed in 52% aqueous HO for 15
hours, it was converted, as shown by elemental analysis, to
6)0.026]X Chasm annuluses)
No oxygen was incorporated into the material.
As disclosed by MacDiarmid and Hedger in Septic
Materials 1, 101 (1979/80), pro tonic acid doping of (SHUCKS by
the vapors from strong acids such as HC104 or H2S04 to
give doped (Shucks having high metallic conductivities of about
10 ohm tam 1 can be had. For example, when (Shucks film
was exposed to the vapor from 70~ aqueous HC104, a material
was obtained having a composition by elemental analysis of
either
[Shekel 127(H2)0-297 x
or
[Shekel 127(H2)0.2971x
according to whether it is assumed that a proton is present or
not. Thermoelectric power studies of the HC10~ doped film
show the doping is p-type.
The oxygen present in the form of H502 or H20 is
therefore zither not combined with the carbons of the OH chain
or, if it is combined with those carbons, then it somehow does
not impair the conductivity of the material. If the water i
combined with the carbons, then this should reduce the pi
conjugation and reduce the conductivity of a polyacetylene
chain. However, experimentally, the conductivity is
increased. If it is not combined with the carbons, this is
I
most surprising, since p-doped polyacetylene is a carbonium ion
and carbonium ions are known to react instantly with water.
Either of these explanations is most surprising and does not
fit in with the present picture of the bonding in p-doped
(SHUCKS or with the understanding of the chemical reactivity of
carbonium ions heretofore known.
The electrochemical undoing in aqueous solution of
conjugated Immures in accordance with the present invention
has not been known. Undoing is necessary to have a
rechargeable battery or a fuel cell. The attainment of
electrochemical doping in aqueous solution does not imply that
electrochemical undoing can be performed. In this regard,
numerous, irreversible fates for carbonium ions or carbanions
generated through the doping reactions could take place and,
according to the prior art, would have been expected.
Furthermore, the observation that electrochemical p-doping of
polyacetylene in aqueous solution can be performed does not
imply that chemical p-doping (or n-doping) in aqueous solution
will be possible. Numerous examples of electrochemical
oxidations taking place in systems wherein chemical oxidation
does not proceed are known. Moreover, the transitory oxygen
p-doping of cis-polyacetylene to a maximum conductivity of
about 10 ohm tam 1 is inapposite to the present
invention. In this regard, the modification of conductivity is
attended by proximate, immediate, degradation of the
polyacetylene film itself. Only through the employment of
do pants in accordance with the present invention is a useful
conductivity modification possible in this system.
The polymers which are suitable for use in connection with
the present invention are polymers having conjugation along the
main backbone chain thereof and which are capable of being
electrochemically oxidized to a p-type doped material and
electrochemically reduced to a n type doped material. While
-the present invention is related to doping in erotic media,
identification of the polymers which may be employed in
connection with this invention is best accomplished by
reference to Us S. Patent 4,321,11~ issued March 23, 19~2~
I: 1
- 13 -
Preferred among the polymers which are suitable for employment in
the present invention are the polyacetylenes and polyphenylenes~
Methods for reversible doping of polyacetylenes and other polymers
with the present invention, together with methods for the con-
struction of secondary batteries, may similarly be had from a
review of the foregoing patent and patent application.
The construction of fuel cells in accordance with the
present invention, together with the preparation of electrolytic
cells for the electrolysis of certain compositions will be
apparent to those of ordinary skill in the art from a review of
the specification, especially the examples. To provide additional
instruction in such construction, the publication Fuel Cells:
Their Electrochemistry, Buckers et all McGraw Hill is mentioned.
The following examples have been prepared more fully to
elucidate the present invention. It is believed that those of
ordinary skill in the art will have no difficulty in ascertaining
what polymers, do pants, media and related materials are suitable
for inclusion in the present invention and that the same persons
will require but routine experimentation to ascertain useful
electrolytic systems for performing the various embodiments of
this invention in view thereof It is to be understood that the
following examples are offered by way of illustration only and are
not to be construed as limiting.
,,~ j
.
- 14 -
Use of 48~ Aqueous HBF4 Electrolyte
Example 1
Polyacetylene, (SHUCKS, does not react chemically to any
significant extent with the non oxidizing acid, HBF4, in its
commercial 48~ solution. For example, when a strip of Claus rich
(SHUCKS (tam x 0.5cm) was immersed in a degassed solution of
48% aqueous HBF4 for 4 hours and pumped dry for 18 hours, the
two-probe conductivity of the film was 6.4 x
-4 -1 -1 well below the semiconductor-metal
transition.
~2~93~ h
- 15 -
Example 2
A series of experiments was carried out in order to
determine if p-doped (oxidized) (SHUCKS is stable in 48%
aqueous HBF4. A piece of is rich (SHUCKS (2cm x 4cm) was
initially electrochemically doped in 0.5M
(Bu4N)(BF4)/cH2cl2
to about I (measured by the number of coulombs passed). The
doped film had a measured two-probe conductivity of 122.5
ohm tam . The film was then cut in half. One half was
sent out for chemical analysis and was found to have a
composition of
[Cal byway FOE 0.100 X
The other half was immersed in degassed 48% aqueous HBF4 for
24 hours, pumped dry for 18 hours, and finally sent out for
elemental analysis After immersion and pumping, the film
still appeared golden and had a measured two-probe conductivity
of 5~.3 ohm lo . The elemental analysis of the aqueous
HBF4-immersed sample was
1.08 0.0804 0.214 0.163]x
Mote that the boron content increased slightly. Moreover, the
hydrogen and oxygen contents (by difference) increase as well.
This can be viewed as an inclusion of HO or the further
hydrolysis of BF4 to B 3 or BF2(OH)2 . However,
it is important to note that polyacetylene retained its Dupont
and remained in the metallic conducting regime.
Lo
Example 3
In a second series of experiments, a piece of is rich
(SHUCKS (tam x 2cm) was initially electrochemically doped in
0.5M (Bu4~)(BF4)/CH2C12 to about I as before. The
doped film was then cut in half. The first tam piece of
[CH~Y(BF4)y]x and a piece of lead were placed in a
degassed solution of O.OlM Pb(BF4)2 in 48~ aqueous HBF4.
The open circuit voltage (VOW) of this cell was 0.810V. The
cell was immediately discharged at a constant current of
Moe until the discharge voltage of the cell fell to 0.2V
representing the approximate point where hydrogen bubbles off
the platinum current collector. 1.231 coulombs were produced
corresponding to about 3.9~ discharge. An identical experiment
with the other half of the doped material was performed except
that the cell was allowed to stand for 18 hours before
discharge. The initial open circuit voltage of this cell was
0.818V and the open circuit voltage after 18 hours was
0.6610V. The cell was then discharged at a constant current of
Moe until the discharge voltage of the cell fell to 0.2V.
The number of 1.170 coulombs, corresponding to about 3.7%
discharge were produced. Hence, little, if any, Dupont was
lost after 18 hours of immersion in 48~ aqueous HBF4. ray
the open circuit voltage drops from about 0.82V to about 0.66V
over 18 hours is not known at the present time, although it
appears likely that it may be due to diffusion equilibrium of
the BY ion between the exterior and interior of the (SHUCKS
fibrils.
- 17 -
Example 4
In a third series of experiments, a lcm2 piece of
SHEA Y(BF4)y~x and a piece of Pub were placed in O.OlM
Pb(BF4)2 in 48% aqueous EIBF4. As in Examples 2 and 3,
the initial open circuit voltage of this cell is typically
about 0.8V and the short circuit current (Is) is typically
about Moe. This cell was successfully cycled two times
(discharge/charge) at a constant current of Moe to/from a
discharge voltage of about 0.2V. It appears that doped
(oxidized) (Shucks can be electrochemically reduced,
electrochemically deoxidized and electrochemically reduced
again in 48% aqueous BF4. The coulombic efficiency of the
second and third steps above was about 53%. After two complete
cycles (discharge/charge) the open circuit voltage was OVA
and the short circuit current was Moe. Little, if any
decomposition of the (SHUCKS was visually observed upon this
cycling of the system. Attempts to oxidize neutral (SHUCKS to
the metallic regime in 48~ aqueous HBF4 were unsuccessful.
However, films of polyacetylene, (SHUCKS can be reversibly
oxidized and reduced in aqueous solutions of the non-oxidizing
acid HBF4 if the (Shucks is first "activated" by aprotically
p-doping it with BF4 in (Bu4~)(BF4)/CH2C12
solution. From the foregoing, batteries can be constructed
utilizing either p-doped (oxidized) (Sioux or "activated"
(Shucks, i.e., (SHUCKS which has been electrochemically
oxidized in an aprotic solvent and electrochemically reduced in
48% aqueous HBF4.
I
- 18 -
Stabilization of p-doped (SHUCKS in the Metallic Regime to Air
It has previously been believed that oxygen (in air
destroys electrical conductivity of p- and n-doped
polyacetylene~ It has now been found that 2 can actually be
used to increase the conductivity of (Shucks to the metallic
regime by p-doping and that (Shucks may be stabilized towards
oxygen in its highly conducting metallic, p-doped state by
treating it with certain acids.
I
Example 5
The first series of experiments was carried out in
order to determine if SHEA) could be chemically oxidized by
2 with the incorporation of a suitable counter anion. A
strip of Claus rich (SHUCKS film (tam x 0.5cm) was placed in a
solution of 48~ aqueous HBF4. Two platinum clips wore
attached to each end of the (SHUCKS film. Oxygen gas was
bubbled over the (SHUCKS film and the resistance of the film
monitored as a function of time. The resistance dropped
rapidly at first but leveled off after about 4-6 hours. The
film was dried in vacua and its two-probe conductivity
measured. In several identical experiments, the p-doped
(oxidized) material had a two-probe conductivity between about
0.1 ohm tam 1 and 1 ohm tam 1.
I
- 20
Example 6
In a similar experiment, a strip of Ox film
(leukemia x 0.5cm) was wetted with 48% aqueous HBF4 and allowed
to stand in 2 gas at about 700 torn. Again, the resistance
dropped rapidly at first but leveled off after about 18 hours.
The film was pumped dry and its two probe conductivity
measured. In several identical experiments, the p-doped
oxidized material had a two-probe conductivity between 0.1
ohm tam 1 and 1 ohm cm
I
Example 7
It was confirmed that 2 acts as the oxidizing agent
in Examples 5 and 6. Two pieces of Claus rich (CHjX (tam x
0.5cm) were mounted in two four-probe conductivity
apparatuses. Each piece of film was wetted with 48~ aqueous
HBF4 for 30 minutes and separately evacuated. 2 gas,
about 700 torn, was introduced to one while I gas, about 700
torn, was introduced to the other. The resistance of the
samples was monitored as a function of time. After 5 days the
four probe conductivity of the material in the oxygen
atmosphere was about 0.83 ohm cm , while the four probe
conductivity of the material in the nitrogen atmosphere was
1.47 x 10 ohm cm . The conductivity exhibited by the
latter film is believed to be due to the ionic conductivity of
the aqueous HBF4 wetting the film and/or to the presence of
traces of 2 in the I gas.
I
- 22 -
Example 8
A second series of experiments was carried out in
order to determine whether (SHUCKS can be stabilized towards
oxygen in its highly conductive, metallic, p-doped state.
(SHUCKS was doped in 0~5M (BU4~)(BF4~/ 2 12 to about
6% as in Example 2. The film was then cut in half and each 2cm
x 0.5cm piece was mounted to a four-probe conductivity
apparatus. One piece was wetted with 48~ aqueous HBF4 while
the other was loft dry. Both pieces were exposed to the air
and the resistance of the samples monitored as a function of
time. The data are reported in Table I. It is apparent that
2 is capable of oxidizing (SHUCKS to the metallic regime and
that this oxidization can be stabilized with certain acids such
as aqueous HBF4.
Table I
Wetted Unwetted
Time (hr.) (ohm-lcm-l) (ohm-1cm-1
0 1.36 x 102 2.50 x 102
168 2.05 x 101 1.4g x 10
336 1.70 x 101 3.54 x 10 1
504 6.1~ x 10 7.36 x 10 2
672 1.25 x 10 1.93 x 10 2
~23~
- 23 -
Material from Examples 5-8 - rationale
These results stem from our recent discoveries based
in part on the two redo equations listed below:
(SHUCKS (OH Yucca E (vs. NAVAHO
2H2 OWE eye E (vs. NAVAHO
Net reaction:
4(CH)x~xyO2~4xyHBF~ SHEA Y(BF~)y~x+2XyH20
THE refers to the Standard Hydrogen Electrode.
The value of fox varies according to the value
of "y". When "y" is infinitesimally small, i.e.
when one is measuring "parent unhoped (SHUCKS,
fox is about ~0.6V (vs. NO using the
convention that H eye has an E ox=+3.05V
vs. THE). The value of fox becomes more
negative as the value of "y" increases. For
example, when yo-yo then EoX=0.63V vs. THE.
From our discoveries it becomes apparent that,
thermodynamically, oxygen will want to oxidize (SHUCKS to
(OH Yucca If only oxygen and water are present then
the counter anion for the (OH Yucca species must be
something such as OH , -1 ' or -2 Such
oxygenated species will combine with (SHUCKS and destroy
it, giving either C-OH and/or COO bonds. If, however,
another counter anion other than the oxygen containing
species is present, e.g., the BF4 ion, then the BF4
ion will combine with the (OH Yucca to give a species
such as [OH Y(BF4)y]x which will be stable in the
presence of oxygen and water once it has obtained its
fully oxidized state in the presence of oxygen. It is not
necessary to use free acid. Solutions of other aqueous
acids such as HPF6, HC104 may be used instead of
HBF4.
The above stabilizations refer to stabilization in
acidic medial however stabilization may also be brought
about in neutral or basic media as given by the redo
reaction below.
40H Owe (lMbase) Eox(vs. NAVAHO
OX
- I -
Use of (OH) as a Fuel Cell Electrode
Polyacetylene, Ox can be used as a fuel
cell electrode. We have discovered that p-doped
(oxidized) (SHUCKS can act as an oxidizing agent whereas
neutral (SHUCKS, either "as synthesized" or previously
"activated", can act as a reducing agent for a variety of
organic and inorganic compounds in erotic media,
especially aqueous media.
sample 9
It was found that neutral "as formed" Claus rich
SHUCKS either did not react electrochemically or reacted
to produce small currents. If, however, it was first
"activated" as disclosed below, its electrochemical
characteristics as an electrode nearly always were
extremely improved. The exact nature of the activation
process and/or mechanism is not yet known.
A series of experiments were carried out in order
to determine if "activated" (SHUCKS could act as a
reducing agent. "Activated" (SHUCKS was prepared as
follows: a tam piece of [OH Y(BF4)y]x
synthesized as in Example 2, and a piece of lead were
placed in a solution of I aqueous HBF4. A Pi clip was
previously attached to the top of the
[OH Y(BF4)y]x and the Pi clip was covered with
paraffin wax in order to isolate the Pi from the
solution. The electrodes were about loom apart in a
"U-cell" type configuration divided into two compartments
by a glass Fritz The open circuit voltage (Vow) of this
cell was about 0.68V. The doped film was then discharged
at a constant potential of OVA versus lead. The
current dropped from 18.OmA to Moe in about one hour
to give a final Vow of about 0.2V, characteristic of
almost completely "unhoped", i.e. neutral (OH) .
2 gas was then bubbled over the strip of
activated (SHUCKS. The current immediately rose to about
Moe and remained at that level for 2 hours. The
:~23'~
- 25 -
experiment was then arbitrarily terminated The number of
coulombs passed was 4.83 C, corresponding to the passage
of 0.181 electrons per OH unit in the (Shucks A
significant current flowed only when 2 was passed over
the (SHUCKS electrode. When the 2 gas was stopped, the
current immediately dropped from about Moe, leveling off
at about Moe after about 1 hour. It is apparent that
(SHUCKS is acting as a "catalyst" or a "fuel cell
electrode", the fuel being lead in this case and the 2
acting as oxidizing agent. The 2 oxidizes the (SHUCKS
chemically to [OH Y(BF4)y]x which is then
immediately reduced electrochemically by the lead. The
composition of the (SHUCKS is believed to remain
essentially unchanged during the reaction. The net
reaction is believed to be:
2Pb+02+4HBF4 2Pb(BF4)2~2H20
- 26 -
Example 10
A lcm2 piece of is rich (OH) "activated" in
x
accordance with Example 9 was allowed to discharge at a
constant potential of OVA versus lead for 24 hours while
2 was constantly bubbled over it. The average discharge
current for the 24 hr. period was Moe and the total number
of coulombs produced was 58.35C, corresponding to the transfer
of 2.187 electrons per OH unit in the (SHUCKS. This experiment
was repeated with a tam piece of is rich (OH)
"activated" in accordance with Example 9. Instead of using a
Pi wire clip as the current collector, a thin carbon sheet was
connected to the (SHUCKS using electrodag. The cell was
allowed to discharge at a constant potential of OVA versus
lead for 24 hours Chile 2 was constantly bubbled over it.
The average discharge current for the 24 hour period was
Moe and the iota' number of coulombs produced was 30.729C,
corresponding to the transfer of 0.9113 elections per OH unit
in the (Shucks.
- 27
Example 11 2
A tam piece of [CH~y(BF4)y]X activated in
accordance with Example 9 and a carbon rod were placed in a
solution of 48~ aqueous HBF4 in a "U-cell" type configuration
divided into two compartments by a glass Fritz A Pi clip was
previously attached to the top of the [OH ~(BF4~y]X and
the Pi clip was covered with paraffin wax in order to isolate
the Pi from the solution. A 50/50 Volvo hydrazine/water
mixture was added to the carbon rod compartment. The open
circuit voltage (VOW) of this cell was about 0.84V. The
doped film was then discharged at a constant potential of
0.000~ between the two electrodes. The current dropped from
Moe to O.lOOmA in 30 minutes. 2 gas was then bubbled over
the strip of activated (SHUCKS. The current immediately rose
to about Moe and slowly dropped to Moe in 2 hours.
Bubbles of No gas were observed forming on the carbon rod.
The number of coulombs passed was 2.469C, corresponding to the
passage of 0.0694 electrons per OH unit in the (SHUCKS. The
2 oxidized the (SHUCKS chemically to [OH Y(BF4)y]x
which is then immediately reduced by electrons liberated by the
reduction of the N2H4 at the C rod, which are transferred
to the SHEA Y(BF4)y~x via the external wire. The
composition of the [OH Y(BF4)y~x is believed to remain
unchanged during the reaction. The net reaction is thought to
be:
N2H4+02 N2+2~12
The reduction in the current during the two hour experiment
is believed to be due to the 50/50 NOAH mixture being
alkaline. this mixture slowly neutralizes the acidic media in
which the (SHUCKS electrode is immersed.
I
- 28
Example 12
A 1.5cm x 2cm piece of c1s rich (SHUCKS film and a
strip of Pub wire were immersed in an 0.5M Pb(C104)2
solution in 12 M HC104. The electrodes were about loom
apart. After equilibrium for four hours the (SHUCKS exhibited
an Eon (vs. Pub) of 0.85V indicating chemical doping of the
(SHUCKS. The two electrodes were connected via an ammeter and
a (very large) short circuit current of Moe was observed.
The short circuit discharge was continued for 18.5 hours after
which the short circuit current had dropped to lima. A white
precipitate of PbC12 coated the polyacetylene film and was
present at the bottom of the cell. The 1077 coulombs which had
passed during this time corresponded to 14.4~ positive charges
being placed on each (OH) unit, i.e. to 1445% doping of the
(SHUCKS, if the charges had remained on the (SHUCKS. The
results of this experiment can be explained in the following
manner. Upon connecting the chemically oxidized (OH)
electrode, i.e. [OH Y(C104)y]x, and the lead electrode,
the (SHUCKS electrode is reduced electrochemically by the
lead. As soon as the (Shucks is even slightly reduced, the
acid immediately chemically oxidizes it back to
[OH Y(C104)~]x This series of electrochemical
reductions and chemical oxidations can go on continually until
it is mechanically slowed down by the deposition of insoluble
PbC12 on the surface of the (SHUCKS film. The net reaction
is believed to be
8Pb~16HC104 7Pb(C104)2+PbC12~8H20
~23~
- 29 -
Example 13
Example 12 was repeated with a tam x 2cm piece of is
rich (SHUCKS film. The cell had an initial short circuit
current of Moe and ran a small electric motor in excess of 6
hours. The surface of the film was then coated with a PbC12
precipitate. The film was washed briefly in water to dissolve
some of the PbC12 and replaced in the cell. An Eon (vs.
Pub) of 0.82V was obtained after 5 minutes and a short circuit
current of Moe was then observed. The motor could then again
be run by the cell.
1;~3~
- 30 -
Example 14
A tam piece o-f is rich (SHUCKS film attached by a
Pi wire clip at the top and a carbon rod were immersed in a 12M
HCl04 solution. The electrodes were about loom apart in a
"U-cell" type configuration divided into two compartment by a
glass Fritz A 50/50 Volvo hydrazine/water mixture was
added to the carbon rod compartment. After equilibrium for
30mm, the open circuit voltage (V0c) was 0.814V. The cell
was allowed to discharge at a constant potential of OVA. An
initial short circuit current of Moe was observed. The short
circuit discharge was continued for 2 hours after which the
short circuit current had dropped to Moe. Bumbles of No
gas were observed on the carbon rod. About 11.43C had passed
during this time corresponding to the passage of 0.257
electrons for each OH unit in the (OH) .
The reduction in the current during the two hour
experiment is believed to be due to the fact that the 50/50
N2H4/H20 mixture is alkaline and that this then reacted
in the pores of the glass fruit to precipitate insoluble
(~2H5) +(C104) in the pores of the Fritz Such a
clogging of the fruit would impair free movement of ions through
the fruit and hence reduce the current.
~;23~
Example 15
A cell similar to that of Example 9 was prepared
having an open circuit voltage (Vow) of 0.778 V. The doped
film was then discharged at a constant potential of OVA us
Pub. The current dropped from Moe to Moe over 30
minutes Benzoquinone was then added to the "activated"
(OH) compartment; the current immediately rose to about
Moe, slowly dropping to about Moe after 2 hours. The
number of coulombs produced was 37.117C corresponding to the
passage of 1.391 electrons per OH unit. The (SHUCKS acted as a
"catalyst", i.e. as a "fuel cell electrode", the fuel being
lead and the oxidizing agent being benzoquinone. The
benzoquinone oxidized the (OH) chemically to
[OH Y(BF4)y]x which was then immediately reduced
electrochemically my the lead. Hydroquinone and lead
floroborate were produced overall. The composition of the
(SHUCKS appeared to remain unchanged during the reaction. The
overall reaction may be represented by the following equation
0= =0~2HBF4~Pb HO- -OH+Pb(BF4)2
The reduction in the current during this two hour
experiment is believed to be due to the fact that insoluble
hydroquinone is deposited on the surface of the (SHUCKS film.
-- 32 --
Example 16
A piece of Claus rich SHUCKS (tam x 2cm) was initially
doped in 0.5M (Bu4N)(BF4)/CH2C12 to about 6% as in
Example 2. The doped film was then cut in half and the two
places of [OH Y(BF4)y]x were placed in a solution of
48~ aqueous HBF4 about loom apart in a "U-cell" type
configuration which was divided into two compartments by a
glass Fritz The open circuit voltage of this cell was, of
course, OVA. Benzoquinone was added to one compartment and
Crook was dissolved in the other. The open circuit voltage
immediately rose to about lo and stabilized at 1.123V after
about 30 minutes. The film immersed in the benzoquinone/48%
aqueous HBF~ solution was oxidized to a higher oxidization
level while the film immersed in the Crook aqueous HBF4
was believed to be reduced to neutral (Shucks since the film
lost its golden color, characteristic of oxidized film. The
cell was discharged at a constant potential of OVA, oxidizing
Or 2 to Or 3 while reducing the benzoquinone. The initial
short circuit current was Moe which fell to Moe after
about 4 hours. A total of 17.257 coulombs were produced. This
corresponds to the passage of 0.495 electrons per OH unit. The
overall reaction may be represented by the following equation
cry OH HO -Okra
I
- 33 -
Example 17
An analogous experiment to Example 16 was performed
where Crook was replaced with hydrazine. Benzoquinone was
added to one compartment of the "U" cell and a 50/50 Volvo
hydrazine/water mixture was added to the other. The pi of the
hydrazine/water mixer was still less than 0. The film
immersed in the benzoquinone/48% aqueous ~F4 solution was
spontaneously chemically oxidized to a higher oxidization level
while the film immersed in the hydrazine/48~ aqueous ~BF4 was
spontaneously chemically reduced and some bubbles appeared on
its surface. The cell was discharged at a constant potential
ox OVA. The initial short circuit current was Lomb and
Poll to Moe after 2 hours. About 3.556 coulombs were
produced corresponding to the passage of 0.128 electrons per OH
unit.
1~3~
34
Example 18
An analogous experiment to Example 17 may be performed
where benzoquinone is replaced with oxygen. Oxygen gas would
be bubbled in one compartment of the "Swahili" and a 50/50
Volvo hydrazine/water mixture added to the other. The
hydrazine/water mixture would be acidic. The film over which
oxygen is bubbled in 48% HBF4 would be spontaneously,
chemically oxidized to a higher oxidation level while the film
immersed in the hydrazine/48~ aqueous HBF4 would be
spontaneously, chemically reduced and some bubbles would appear
on its surface indicating progress of the reaction.
While final evaluation of Example 17 has not yet been
made, the results for that example as well as for example 16
and those expected for Example 18 demonstrate that
[OH Y(BF4)y]x can act as a good oxidizing agent. Both
cry and H2NNH2 were believed to be oxidized by
[OH Y(BF4)y]x to Cry and No respectively. In
conclusion, it is apparent that (Shucks (especially when
activated) either or [OH Yucca can act as an electrode
in fuel cell type processes in erotic media either for the
reduction or oxidation of a variety of organic and inorganic
chemical species.
Lo
35 -
Chemical p-doping of (SHUCKS in aqueous solution
Example 19
A piece of Claus rich (SHUCKS film (1.4cm x .4cm) was
attached to two platinum clips and immersed in an aqueous
solution of H2S04. The resistance of the film was
monitored versus time. Identical experiments were carried out
with degassed EM, EM 12M, 15M, and 18M aqueous H2S04
solutions. Both the log vs. time for each specified
concentration as well as the after 30 minutes versus polarity
were plotted in Figures 1 and 2 respectively. It can be seen
that (SHUCKS undergoes a semiconductor-metal transition in
aqueous solution The conductivity at first slowly increases
from 10 ohm cm and then suddenly increased from about
4 h -1 -1 to 140 ohm~lcm-l as the acid
concentration was increased from 12M to 18M. When the
resulting flexible golden film was removed from the 18M
solution and was washed with cyclohexene (to remove H2S0~)
the film still had a conductivity of about 100 ohm tam
The reaction occurring is believed to be represented by the
following equation
2(CH)x~3xyH2SO4 SHEA Y(HS04)y~x~~XyH2S03+XyH20
It is possible that the H2S03 may, itself, also be reduced
further.
I
- 36 -
Example 20
In an experiment similar to Example 19, a piece of Claus
rich (SHUCKS film (1.4cm x 0.4cm) was attached to two platinum
clips and immersed in an aqueous solution of HC104. The
resistance of the film was monitored us time. Identical
experiments were carried out with degassed EM, EM, EM and 12M
aqueous HC104 solution. Both the log versus time for each
specified concentration as well as the after 30 minutes
versus polarity were plotted and are shown in Figures 3 and 4
respectively. The (Shucks undergoes a semiconductor-metal
transition in aqueous HC104 solution. Note that the
conductivity increased from about 5xlO ohm cm to
about 5 ohm tam 1 and finally to about 350 ohm tam 1 as
the acid concentration was changed from EM to 12M. The
reaction occurring is believed to be represented by the
following equation
SHEA) +9xyHC104 SHEA Y(C104)y]x+xyHC1+xyH20
The studies of Examples 19 and 20 demonstrate that
strong, aqueous H2S04 and HC104 can chemically p-dope
(SHEA film immersed therein. The reaction occurring when
(SHUCKS is immersed in strong H2S04 or HC104 is believed
to involve the reduction of the acid and the concomitant
oxidation of SHUCKS. The conductivity increases with
increasing acid concentration. It is believed that as the
concentration of acid increases, the (SHUCKS becomes more
highly doped since it is know that for (SHEA the conductivity
is related to the level of Dupont. From Figures 1-4, it can be
concluded that (SHUCKS can undergo a semiconductor-metal
transition in acidic aqueous solution.
~L;23~
- 37 -
Electrochemical p-doping of (SHUCKS in Aqueous Solution
Example 21
When Claus rich (Shucks film is immersed in 50% aqueous
HO for 1 hour and is then pumped in a vacuum system for 18
hours, no experimentally observable increase in weight or
conductivity is observed.
I
3B -
Example 22
When a piece of c1s rich (SHUCKS film (1.5cm x 2.0cm)
is used as the anode and platinum foil as the cathode in 50% HO
and a potential of Levi is applied for a period of 20 minutes,
the shucks film becomes doped. After washing in 50~ HO and
pumping in a vacuum system for 18 hours a flexible, golden film
having a conductivity of about 1 ohm tam 1 was obtained.
Elemental analysis gave a composition corresponding to
[Cal 06Fo.og3O.O91]x It is believed that this may
have a constitution such as [SHEA (HF2)0 owe 09] .
I
- 39 -
Example 23
A tam piece of Claus rich (SHUCKS film and a piece of
lead foil were placed in a saturated solution of PbF2 in 50
aqueous HF. After 30 minutes Eon (vs. Pub) equaled 0.60V.
This implies some chemical doping in the presence of aqueous
HF. The (SHUCKS was then attached to the positive terminal of
a do power supply and oxidized for 30 minutes at a constant
current of Lomb. This corresponds to about I p-doping of the
(SHUCKS. The Eon (vs. Pub) 30 minutes after discontinuance of
the do current was 0.81V. On connecting the (SHUCKS and Pub
electrodes via an ammeter a surprisingly large short circuit
current of Moe was observed. It is concluded that the
(SHUCKS is electrochemically oxidized upon application of the
do current and that this reaction is, at least in part,
electrochemically reversible.
I
- 40 -
Example 24
Two pieces of Claus rich (SHUCKS film (tam x 1~5cm) and
a piece of platinum foil were placed in a saturated solution of
PbF2 in 50% aqueous HF. Fact piece of (SHUCKS in turn was
attached to the positive terminal of a do power supply and
the platinum attached to the negative terminal. A constant
voltage of 1.0V was applied to give about I oxidation of the
(SHUCKS. The do power supply was then connected to the two
pieces of oxidized (SHUCKS, placed 10mm apart, each having a
(assumed) composition of [OH (HF2) o 03]x A
constant voltage of 1.0V was applied for a period so that the
same number of coulombs used in the original oxidation of each
piece of film had passed. It was assumed that one piece of
film now had a composition of [OH ' HO o 06]x~ and
the other a composition of (OH) . Upon connecting the two
pieces of film via a voltmeter, a potential difference of 0.71V
was observed. On connecting them via an ammeter a relatively
large short circuit current of Moe was obtained. These
results strongly suggest a reversible electrochemical reaction
involving (SHUCKS.
I
- 41 -
Example 25
A piece of is rich (SHUCKS film 2cm x 3cm and a piece
of platinum foil were placed in a saturated solution (0.5M) of
NaAsF6 in 50~ HF. The (SHUCKS was attached to the positive
terminal and the platinum to the negative terminal of a do
power supply. A constant potential of Levi was applied between
the electrodes for about 30 minutes. The film was then washed
in 50% HO and pumped in a vacuum system for 18 hours. In
several different experiments flexible, golden, p-doped films
having good metallic conductivities of about 10 to 100
hm-lcm-l in the metallic regime were obtained.
Significantly, the films contained no oxygen. The F content
varied from one preparation to another, e.g.
[Showoffs 1)0.026]x
and
[SHOWOFF 7)0.029]x
The nature of the Dupont species and the cause of the variable
F content is not presently known
- 42 -
Example 26 2
A platinum mesh was folded around a tam piece of
Claus rich (SHUCKS film and placed loom apart from a piece of
lead wire in a saturated solution of PbF2 in 50% HO which was
also 0~5M in NaAsF6. The (SHUCKS electrode and the Pub
electrode were attached to the positive and negative terminals
respectively of a do power supply and a constant current of
coma was passed for 30 minutes. This corresponded to an
approximately 8.1% oxidation of the (OH) . e ox
Pub) of this oxidized, shucks was 0.95V. On connecting the two
electrodes via an ammeter a large short circuit current of
Moe was observed. In an identical experiment, the (SHUCKS
was found to have an Eon (vs. Pub) of 0.57V after sitting in
the electrolyte for 30 minutes prior to any electrochemical
studies. Oxidation to 8.1% was carried out as before. Thirty
minutes after the oxidation was terminated the oxidized (SHUCKS
exhibited an Eon (vs. Pub) of 0.80V. A short circuit current
of Moe was then observed. A reversible, electrochemical
reaction appears to occur in the system strongly suggesting its
potential usefulness as a storage battery cell.
I 3
- I
Example 27
Two 1.0cm x 1.5cm is rich (SHUCKS electrodes attached
to a platinum wire current collector were placed in an 0.5M
NaAsF6 solution in 50% HF. A platinum foil electrode was
also placed in the solution. Each piece of (SHUCKS film was
oxidized separately to about 3% (calculated by the number of
coulombs passed) by attaching the film to a positive terminal,
respectively of a do power supply. The electrochemical
oxidation of the (Shucks was carried out at a constant applied
potential of 1.0V. The two pieces of (SUE 10mm apart in the
electrolyte were then attached to the positive and negative
terminals of a do power supply at a constant applied
potential of 1.0V. The number of coulombs passed were such
that one piece of oxidized (SHUCKS was reduced to neutral
(SHUCKS and the other further oxidized to about I The open
circuit voltage then observed between the two pieces of film
was 0.68V. On connecting the two pieces of film, a short
circuit current of Moe was observed. After a 30 minute
short circuit discharge, the current had fallen to 0O01mA
representing a 17% coulombic efficiency. Accordingly, this
system has potential as a rechargeable storage battery cell.
I
- 44 -
Example 28
In several separate experiments using a saturated
solution of NaPF6 in 50% HO as an electrolyte, 1.5cm x 2.Ocm
pieces of (SHUCKS film were attached to the positive terminal
and a piece of platinum foil was attached to the negative
terminal of a constant potential (1.25V) do power supply for
about 30 minutes. The (Shucks was oxidized to about 7.0~ by
this process. After washing with 50% HO and pumping for 18
hours in vacua, flexible, golden films having conductivities in
the metallic regime, 30 to 70 ohm tam 1, were obtained.
Elemental analyses from two experiments gave compositions
corresponding to
[CHl.04PO.0081 0.10 0.13]x
and
[Cal llPO.0071FOol4 0.05 x
oxygen (by difference) is apparently present, possibly in the
form of water of hydration. The very small phosphorus content
is unexplained although it may be that the phosphorus is
present as an impurity due to incomplete removal of the NaPF6
during the washing process.
These results show that lCH)X can be electrochemically
oxidized in aqueous Solon and that even though oxygen is
incorporated in some way into the film the conductivity of the
material obtained is well into the metallic regime.
I
45 -
Example 29
Several experiments were carried out in an identical
manner to those described in Example 24 except that a saturated
solution of Nab in 50~ HO was employed in lieu of the
NaPF6. Golden, flexible films having conductivities of about
1 ohm tam 1 were obtained. Elemental analysis of films
from two separate experiments gave compositions corresponding to
[Cal 05Bo.02~Fo,090,02]X
and
[Cal buff x
Electrochemical oxidation processes occur during the passage of
the electric current in these experiments, but the conductivity
levels obtained are lower than those for the systems in which
NaAsF6 and NaPF6 solutions in 50~ HO were used.
I
- 46 -
Electrochemical p-doping of Polyparaphenylen2, (PUP), in
Aqueous Solution
Example 30
A loom diameter, loom pellet of PUP was annealed in
vacua for 48 hours at 400C. It was then attached mechanically
to a Pi wire and placed in an 0.5M solution of Pb~C104)2 in
12M HC104 loom from a lead counter electrode. The Eon (vs.
lead) of the PUP after a 30 minute immersion in the electrolyte
was 1.08V. At this time it gave a short circuit current of
Moe. It was then attached to the positive terminal and the
lead attached to the negative terminal of a constant current
do power supply for 1 hour at Moe. From the coulombs
passed, the expected composition of the PUP was
[(C6H4) (Kiwi 052]x
(exclusive of chemical oxidation). After standing for 30
minutes in the electrolyte, the doped PUP exhibited an fox
(vs. Pub) of 1.17V and a short circuit current of Moe.
I
- 47 -
Example 31
Example 30 was repeated using EM HC104. The fox
(vs. Pub after 30 minutes was 0.92V and the corresponding short
circuit current was Moe. After oxidizing electrochemically
to a composition corresponding to
~(C6H4) (C104~ o 046~X
(exclusive of chemical oxidation) an Eon (vs. Pub) of 1.18V
was obtained after a 30 minute equilibration period. A short
circuit current of Moe was recorded at that time.
Examples 26 and 27 demonstrate that pol~paraphenylene can
be oxidized electrochemically in aqueous solution in a manner
analogous to (Shucks, and that this system is reversible and
can act as a rechargeable battery cello
I
- I -
(OH) as a Secondary Battery Electrode in HC104 and H2S04
Example 32 2
A tam piece of Claus rich shucks film is doped
overnight in 12M HC104 to yield a chemically 11~ p-doped
material having an Eon (vs. lead) of OVA. This material
was then placed along with a lead counter electrode in an 0.5M
solution of Pb(C104)2 in 12M HC104. When the (SHUCKS and
Pub electrodes of the above electrochemical cell were attached
to the positive and negative terminals respectively of a do
power supply at a constant voltage oxidation of 1.20V for about
8.5 minutes and the power supply was then disconnected, an
immediate Eon (vs. lead) of about l.l9V was observed. The
(OH) had therefore been very highly oxidized
electrochemically in aqueous HC104. The potential fell
during 2 hours, possibly in part because of diffusion of Dupont
species from the exterior to the interior of (SHUCKS fibrils.
The value of Eon (versus lead) after 2 hours was about 0.94V,
corresponding to a doping level of 15%. The (Clucks had been
oxidized in aqueous HC104 to a degree beyond the 11% obtained
by simple immersion of the (SHUCKS film in 12M HC104~ The
E value fell further during the next 24 hour period to
about OVA versus lead corresponding to a doping level of
12.2%, still in excess of that obtained chemically by immersing
(Shucks film in 12 M HC104.
It is believed that the following electrochemical
oxidation of the (SHUCKS occurred during the above "battery
charging" reaction:
[OH 0 11(C104) 0 1l~x+0~02xPb(C10~)2
[OH (C104) 0 15]x+0.02xPb.
During discharge, the reverse reaction to that given
above, the short circuit current observed, after two hours
standing (potential [vs. Pub], 0.94V) was Moe.
Whether the observed decrease in Eon on standing is
due to further slow diffusion of -the Dupont species into the
interior of the (Shucks fibrils or whether it is due to slow
reaction with air, to partial hydrolysis or to some other
factor is not presently known. During the electrochemical
fly
- 49 -
oxidation and during the 24 hour standing period, the apparatus
was exposed to air. All previous polymer batteries using
organic electrolytes would have deteriorated completely in a
few minutes, even at lower doping levels, under aerobic
conditions
It is believed that the battery cell can be repeatedly
recycled between OVA (vs. Pub) and Levi (vs. Pub at high
coulombic efficiency without discernible degradation. Due to
the logarithmic form of the equation relating the potential of
doped (SHUCKS to the percent oxidation, a very small change in
voltage corresponds to a large change in percent doping at
doping concentrations greater than about 10%. This is an ideal
characteristic for an electrode in a secondary battery cell.
Z3~
50 -
Example 33
A battery cell similar to that of Example I was
constructed from a tam , 4mg piece of cls-rich (SHUCKS film
in 0.5M Pb(C104~2/12 M HC104 together with a lead counter
electrode. The cell was "charged" at a constant voltage of
Levi for 25.5 hours. The initial charging current was Moe and
the final charging current was Moe. The short circuit
current after subsequent standing for a period of 24 hours was
in excess of 0.5 ampere and was sufficient to run a small
electric motor and propeller. No previously known type of
polymer electrochemical cell can accomplish this feat using
lcm2 piece of polymer film.
I
Example 34
A lo x 1.5cm piece of Claus rich (SHUCKS film and a
strip of lead were place in 12M H2S04 about loom apart.
After 30 minutes the polyacetylene film had an fox (vs. lead)
of 0.60V. The (SHEA and Pub electrodes were then attached to
the positive and negative electrodes respectively of a constant
voltage (1.25V) dock power supply for 7~5 minutes. The
coulombs passed corresponded to 6% oxidation of the (SHUCKS.
The Eon (vs. Pub) of the (SHUCKS electrode was 1.12V and on
connecting the electrodes via an ammeter a short circuit
current of Moe was observed. These observations suggest that
this system also involves reversible electrochemistry
suggestive of potential secondary battery applications.
'3..ff~3~ LO
All Polymer Electrode Batteries
Example 35
One tam piece of is rich (SHUCKS film was placed
in 12M HC104 containing dissolved Pb(C104)2 together with
a Pub electrode. The piece of (Shucks film was attached to the
positive terminal of a 1.2V deco power source an the lead
electrode was attached to the negative terminal for 8 minutes.
This resulted in the (SHUCKS being oxidized to a greater extent
than that obtained by chemical oxidation in the electrolyte.
The lead electrode was disconnected and a second lo piece
of (SHUCKS placed in the electrolyte and connected to the
first, electrochemically doped, piece of (SHUCKS via a
voltmeter. A potential of 0.30V was observed and an
unexpectedly large short circuit current was obtained (Moe).
After a 15 minute discharge the current had fallen to Moe.
The coulombic efficiency was 48%. This experiment suggests
that a useful all-(CH)x rechargeable cell may be obtainable
in this system. The overall discharge reaction is believed to
be given by the equation.
[OH 'll(C10~) o 11] SHEA 178(C104) o 178]
SHEA ' (C104) o 144]x
~239L~
- 53 -
Example 36
Two tam x 1.5cm pieces of is rich (SHUCKS film were
placed loom apart in a 12M H2S04 solution together with a
piece of Pi foil. Both pieces of (Shucks were oxidized
sequentially and electrochemically to 3% by attaching each one
to the positive terminal and the Pi to the negative terminal
respectively of a 0.75V constant voltage do power supply for
a period of 8.5 minutes. The level of oxidation was calculated
from the number of Columbus passed The two (SHUCKS electrodes
were then attached to the terminals of an 0.75V constant
potential power supply for 4 minutes so that the number of
coulombs passed should oxidize one (SHUCKS electrode to 6% and
reduce the other to neutral (SHUCKS. A potential difference of
0.48V was then observed between the two electrodes. On
connecting them via an ammeter a short circuit current of
Moe was observed. Upon continuing the short circuit
discharge for 10 minutes the short circuit current fell to
Moe. The coulombic efficiency was 23%.
The discharge reaction of this cell is believed to be
Shucks (HS04) o 06]x SHEA ' Sue) O 03] .
Again, this system shows considerable potential for a
rechargeable battery system.
