CA1108690A - Hydrogen/chlorine electrochemical energy storage system - Google Patents
Hydrogen/chlorine electrochemical energy storage systemInfo
- Publication number
- CA1108690A CA1108690A CA298,189A CA298189A CA1108690A CA 1108690 A CA1108690 A CA 1108690A CA 298189 A CA298189 A CA 298189A CA 1108690 A CA1108690 A CA 1108690A
- Authority
- CA
- Canada
- Prior art keywords
- storage system
- carbon
- energy storage
- electrochemical energy
- electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910052801 chlorine Inorganic materials 0.000 title claims abstract description 30
- 239000000460 chlorine Substances 0.000 title claims abstract description 30
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 16
- 239000001257 hydrogen Substances 0.000 title claims abstract description 16
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 15
- 238000012983 electrochemical energy storage Methods 0.000 title claims abstract description 15
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 title description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 50
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 47
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000003792 electrolyte Substances 0.000 claims abstract description 19
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 45
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical group Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 claims description 6
- 229910052736 halogen Inorganic materials 0.000 claims description 4
- 150000002367 halogens Chemical class 0.000 claims description 4
- 230000002035 prolonged effect Effects 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims 6
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 22
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 22
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 14
- 229960000443 hydrochloric acid Drugs 0.000 description 8
- 235000011167 hydrochloric acid Nutrition 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000000034 method Methods 0.000 description 6
- 238000009835 boiling Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 229920006384 Airco Polymers 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000009736 wetting Methods 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000010306 acid treatment Methods 0.000 description 2
- 230000000274 adsorptive effect Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000000654 additive Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000004320 controlled atmosphere Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 229940037395 electrolytes Drugs 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- -1 iron-titanium hydride Chemical compound 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/96—Carbon-based electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/32—Hydrogen storage
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Inert Electrodes (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Hydrogen, Water And Hydrids (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE A HC1 electrochemical energy storage system comprises a cell having therein an aqueous HC1 electrolyte in which at least a portion of the HC1 is present in disassociated form ant an electrode of ungraphitised carbon, and communicating with said cell, at least one member of the group of means for storing hydrogen and means for storing chlorine, said means for storing hydrogen comprising graphitised carbon, and said means for storing chlorine comprising un-graphitised carbon.
Description
Canada U-10,611 6~
BACKGROUND OF THE INVENTION
In any electrochemical reaction, the driving force, i.e.
the voltage, is greater than the theoretically necessary voltage and the additional amount of voltage required is known as an overvoltage. Many methods have been used in the past to reduce overvoltage including the use of depolarizers and various structural devices. The problem, however, is complicated be-cause there is an overvoltage associated with each of the gases liberated during the electrochemical reation. One lQ such electrochemical energy storage system is based on electro-lizing aqueous hydrogen chloride.
The use of carbon electrodes, i.e., electrodes manu-factured from carbon, graphite, activated graphite, and the like, is desirable because of a combination of their relatively low cos~ and availability. Unfortunately, such carbon elec-trodes have a significant chlorine overvoltage. In a . ., . . ~.
: . . . . .,, ~ ~ ~
.:
.: . ~ :
6~) document which was available to the public before this Canadian application was filed, a method of considerably and permanently decreasing the oxidation and reduction chlorine overvoltages of such carbon electrodes was disclosed. The method involves contacting the electrode with nitric acid for an effective overvoltage reducing length of time, generally 10 to 1200 hours, preferably 80 to 800 hours, and most prefer-ably 400 to 700 hours. The nitric acid is preferably concen-trated nitric acid and is most preferably boiling B-constant nitric acid.
A means of further reducing the chlorine overpotential in an HCl electrochemical energy storage system in which the aqueous HCl electrolyte contains at least a portion of the HCl in disassociated form has been discovered and, further, new methods of storing the hydrogen and chlorine by-products of the system have also been discovered. Accordingly, it is the object of this invention to provide a means for decreasing the chlorine overvoltages in such a system and means for storing the hydrogen and chlorine by-products. This and other objects of the invention will become apparent to those skilled in the art from the following detailed description.
SUMMARY OF THE INVENTION
-This invention relates to a method of decreasing the chlorine overvoltages of carbon electrodes in a HCl electro-chemical system in which a portion of the HCl is disassociated from the water, and means to storing the hydrogen and chlorine by-products of such a system, through appropriate use of graphitised or ungraphitised carbon.
,.
-36~0 DESCRIPTION OF THE INVENTION
The present invention is based on the differences in behavior of graphitised and ungraphitised carbon electrodes when used in connection with a hydrochloric acid electrolyte.
The performance of such electrodes are very similar in hydro-chloric acid when the concentration is below about 20% but are sharply different when the concentration is above 20%.
The chlorine overpotential behavior difference is evidenced by measuring the anodic chlorine overpotential in millivolts employing 10 milliamps per square centimeter current density.
Using an ungraphitised carbon electrode, the overpotential is substantially constant, being about 7 millivolts at 5% HCl concentration and rises in a substantially uniform manner as the HCl concentration is increased to about 8 mv at 37%
HCl concentration. A graphitised carbon electrode exhibits an anodic chlorine overpotential of about 5 mv over an HCl concentration range between 5 and about 18%. As the HCl con-centration is thereafter increased, the graphitised carbon shows a very sharp anodic chlorine overpotential rise reaching about 45 mv at about 24% concentration. As the HCl concentration is then increased, the graphtised carbon shows an overpotential of about 45-46 mv through the 24-37% HCl concentration range.
The foregoing behavior of the graphtised and ungraphitised carbon electrodes has been observed to be independent of the current density.
In addition to the sharp overpotential/concentration inflection that occurs at about 20% with the graphitised carbon electrodes, hysteresis effects were invaribly observed, particu-larly at low current densities. The hysteresis effects .7 . .
6~0 were markedly absent in the ungraphitised electrodes even at the highest acid concentrations and even at the lowest current density.
It is believed that the foregoing behavior is the result of unassociated hydrogen chloride such as may be present in water mixture, commonly termed hydrochloric acid, being strongly adsorbed into graphitised carbon so as to affect the chlorine overvoltage. This was substantiated as follows. Hydrochloric acid of about 20 weight percent HCl and 80 weight percent water was boiled for about four hours to bring the mixture into exactly the constant boiling proportions. The chlorine overpotentials of graphitised and ungraphitised carbon were then measured in the boiled acid and were 6 and 8 mv re-spectively. Then about 50 grams per liter of titanium tetra-chloride ~which is well known to disassociate some HCl from the constant boiling hydrogen chloride/water mixture) was added to the boiled acid mixture and the overpotentials were again measured. The graphitised carbon overpotential had risen from about 6 mv to about 39 mv. However, the anodic overpotential of the ungraphitised carbon electrode had only risen from about 8 mv to about 9 mv. Then, about 100 grams of water per liter were added to the hydrochloric acid mixture containing the titanium tetrachloride thereby reducing the hydrogen chloride proportion to about 18 weight percent and it was found that the overpotentials at both electrodes had reverted to about their original values, i.e., 6 and 8 mv, respectively. All of the measurements were made at a current density of 10 milliamps per square centimeter.
It has further been observed that the ability of elec-trolytes to wet graphitised carbon is strongly influenced by the presence of hydrogen in the electrolyte. In some instances, ,, j_ .~s .. ~ ~ . , :- . ~ . ..
- . ~ . , ~ , . -in sodium chloride, for example, the presence of hydrogen completely prevents the passage of electrolyte through porous graphitised carbon at reasonable entry pressures, indicating completely non-wetting. On the other hand, the wetting properties of ungraphitised carbon are affected very little by the presence of hydrogen in the electrolyte. Ac-cordingly, the sharp decline in wetting properties of graphitised carbon because of the hydrogen in the water based electrolyte is due to the strong preferential adsorption of hydrogen into the graphitised carbon.
Additionally, the amount of chlorine removed from a circulating electrolyte containing dissolved chlorine by un-graphitised carbon is many times greater than that removed by graphitised carbon. However, the overpotential measure-ments described above show that despite the larger amount of chlorine adsorbed by ungraphitised carbon, the effect on chlorine overvoltage, both anodic and cathodic, is much less than the effect of a smaller amount of adsorbed chlorine on the chlorine overvoltage of graphitised carbon. Where pressures and temperatures are such that liquid chlorine is present, the ; foregoing effects of the chlorine adsorption on the carbon electrode overvoltage are more pronounced, and additionally, some instability is observed in the overpotentials of the graphitised carbon.
The foregoing observations and discussion has the following practical implications:
Firstly, in systems where the hydrochloric acid con-centration exceeds the constant boiling concentration (about 20 percent by weight, depending on the amount of disassociating additives such as titanium tetrachloride), graphitised carbon :
. X
- . . .: . . . .
. ,.. ~ ~ .. :
, : - ., - . :
., . - , 6~0 electrodes result in very high overvoltage inefficiencies and graphitised carbon electrodes are therefore much preferred. This preference extends also to carbon elec-trodes which have been catalyzed in the known manner with known catalysts such as the noble metals. For example, it has been found that platinized, ungraphitised carbon re-sults in much lower overvoltages than platinized, graphitised carbon~
Secondly, in systems where hydrogen storage is required, the storage can be accomplished by hydrogen adsorbtion into graphitised carbon. Such adsorptive storage of hydrogen in graphitised carbon has a great advantage over the known storage means, such as storage in iron-titanium hydride, for example, because it is not effected~by exposure to and contact with the hydrochloric acid electrolyte.
Thirdly, in systems where chlorine storage is required, for example, as liquid chlorine, safety and other advantages accrue from adsorbing the chlorine to ungraphitised carbon, with consequent modification in the pressure/temperature 2Q relationships controlling storage and release.
Fourthly, in systems where the hydrochloric acid concentration does not exceed the constant boiling concentra-tion but where the temperature~pressure relationship dictates the formation of liquid chlorine, graphitised carbon electrodes result in high and unstable overvoltages and, therefore, un-i graphitised carbon electrodes are much preferred.
~` The prolonged nitric acid treatment of carbon elec-trodes which results in sharp reduction of chlorine overvoltages, which has been referred to hereinbefore, does not change 3a but rather enhances all of the characteristic performances ' , : . "
~ 6~
which have been described above. For example, the adsorptive capacity of graphitised carbon for hydrogen chloride, of graphitised carbon for hydrogen, and of ungraphitised carbon for chlorine, are all greatly increased by the prolonged nitric acid treatment of the carbon electrodes The experimental data set forth above was obtained using Airco Speer (trademarkl Grade 37C ungraphitised carbon and Airco Speer (trademark) Grade 37G graphitised carbon, the latter being made by graphitising the former. Graphitising is the process of prolonged heating at very high temperatures in a controlled atmosphere. The very high temperatures are generally above 2,000C at which the carbon allotropic form is converted to the graphite allotropic form at practical rates. Substantially identical results to that achieved with the Airco Speer ~trade-mark~ material has also been obtained using Union Carbide Grade PG60 graphitised carbon and its ungraphitised counterpart.
The use of high HCl concentrations in HCl electro-chemical energy storage systems has generally been avoided because the electrodes are substantiàlly unstable in such a system. It has been found that the ungraphitised carbon electrodes, whether catalyzed or uncatalyzed are sufficiently stable to be of practical use in an aqueous HCl electrolyte of any concentration including concentrations when at least a portion of the HCl is not associated with the water.
Various changes and modifications can be made in the present invention without departing from the spirit and scope thereof. The various embodiments disclosed herein were for the purpose of further illustrating the invention ~' - .
.:. . -: . . . . .
6~
but were not intended to limit it. For example~ it will be recognized that the non-halogen electrode need not be a carbon electrode but can be any other known suitable material.
:: ~,''' ,. '- ,' ' :
: ~
BACKGROUND OF THE INVENTION
In any electrochemical reaction, the driving force, i.e.
the voltage, is greater than the theoretically necessary voltage and the additional amount of voltage required is known as an overvoltage. Many methods have been used in the past to reduce overvoltage including the use of depolarizers and various structural devices. The problem, however, is complicated be-cause there is an overvoltage associated with each of the gases liberated during the electrochemical reation. One lQ such electrochemical energy storage system is based on electro-lizing aqueous hydrogen chloride.
The use of carbon electrodes, i.e., electrodes manu-factured from carbon, graphite, activated graphite, and the like, is desirable because of a combination of their relatively low cos~ and availability. Unfortunately, such carbon elec-trodes have a significant chlorine overvoltage. In a . ., . . ~.
: . . . . .,, ~ ~ ~
.:
.: . ~ :
6~) document which was available to the public before this Canadian application was filed, a method of considerably and permanently decreasing the oxidation and reduction chlorine overvoltages of such carbon electrodes was disclosed. The method involves contacting the electrode with nitric acid for an effective overvoltage reducing length of time, generally 10 to 1200 hours, preferably 80 to 800 hours, and most prefer-ably 400 to 700 hours. The nitric acid is preferably concen-trated nitric acid and is most preferably boiling B-constant nitric acid.
A means of further reducing the chlorine overpotential in an HCl electrochemical energy storage system in which the aqueous HCl electrolyte contains at least a portion of the HCl in disassociated form has been discovered and, further, new methods of storing the hydrogen and chlorine by-products of the system have also been discovered. Accordingly, it is the object of this invention to provide a means for decreasing the chlorine overvoltages in such a system and means for storing the hydrogen and chlorine by-products. This and other objects of the invention will become apparent to those skilled in the art from the following detailed description.
SUMMARY OF THE INVENTION
-This invention relates to a method of decreasing the chlorine overvoltages of carbon electrodes in a HCl electro-chemical system in which a portion of the HCl is disassociated from the water, and means to storing the hydrogen and chlorine by-products of such a system, through appropriate use of graphitised or ungraphitised carbon.
,.
-36~0 DESCRIPTION OF THE INVENTION
The present invention is based on the differences in behavior of graphitised and ungraphitised carbon electrodes when used in connection with a hydrochloric acid electrolyte.
The performance of such electrodes are very similar in hydro-chloric acid when the concentration is below about 20% but are sharply different when the concentration is above 20%.
The chlorine overpotential behavior difference is evidenced by measuring the anodic chlorine overpotential in millivolts employing 10 milliamps per square centimeter current density.
Using an ungraphitised carbon electrode, the overpotential is substantially constant, being about 7 millivolts at 5% HCl concentration and rises in a substantially uniform manner as the HCl concentration is increased to about 8 mv at 37%
HCl concentration. A graphitised carbon electrode exhibits an anodic chlorine overpotential of about 5 mv over an HCl concentration range between 5 and about 18%. As the HCl con-centration is thereafter increased, the graphitised carbon shows a very sharp anodic chlorine overpotential rise reaching about 45 mv at about 24% concentration. As the HCl concentration is then increased, the graphtised carbon shows an overpotential of about 45-46 mv through the 24-37% HCl concentration range.
The foregoing behavior of the graphtised and ungraphitised carbon electrodes has been observed to be independent of the current density.
In addition to the sharp overpotential/concentration inflection that occurs at about 20% with the graphitised carbon electrodes, hysteresis effects were invaribly observed, particu-larly at low current densities. The hysteresis effects .7 . .
6~0 were markedly absent in the ungraphitised electrodes even at the highest acid concentrations and even at the lowest current density.
It is believed that the foregoing behavior is the result of unassociated hydrogen chloride such as may be present in water mixture, commonly termed hydrochloric acid, being strongly adsorbed into graphitised carbon so as to affect the chlorine overvoltage. This was substantiated as follows. Hydrochloric acid of about 20 weight percent HCl and 80 weight percent water was boiled for about four hours to bring the mixture into exactly the constant boiling proportions. The chlorine overpotentials of graphitised and ungraphitised carbon were then measured in the boiled acid and were 6 and 8 mv re-spectively. Then about 50 grams per liter of titanium tetra-chloride ~which is well known to disassociate some HCl from the constant boiling hydrogen chloride/water mixture) was added to the boiled acid mixture and the overpotentials were again measured. The graphitised carbon overpotential had risen from about 6 mv to about 39 mv. However, the anodic overpotential of the ungraphitised carbon electrode had only risen from about 8 mv to about 9 mv. Then, about 100 grams of water per liter were added to the hydrochloric acid mixture containing the titanium tetrachloride thereby reducing the hydrogen chloride proportion to about 18 weight percent and it was found that the overpotentials at both electrodes had reverted to about their original values, i.e., 6 and 8 mv, respectively. All of the measurements were made at a current density of 10 milliamps per square centimeter.
It has further been observed that the ability of elec-trolytes to wet graphitised carbon is strongly influenced by the presence of hydrogen in the electrolyte. In some instances, ,, j_ .~s .. ~ ~ . , :- . ~ . ..
- . ~ . , ~ , . -in sodium chloride, for example, the presence of hydrogen completely prevents the passage of electrolyte through porous graphitised carbon at reasonable entry pressures, indicating completely non-wetting. On the other hand, the wetting properties of ungraphitised carbon are affected very little by the presence of hydrogen in the electrolyte. Ac-cordingly, the sharp decline in wetting properties of graphitised carbon because of the hydrogen in the water based electrolyte is due to the strong preferential adsorption of hydrogen into the graphitised carbon.
Additionally, the amount of chlorine removed from a circulating electrolyte containing dissolved chlorine by un-graphitised carbon is many times greater than that removed by graphitised carbon. However, the overpotential measure-ments described above show that despite the larger amount of chlorine adsorbed by ungraphitised carbon, the effect on chlorine overvoltage, both anodic and cathodic, is much less than the effect of a smaller amount of adsorbed chlorine on the chlorine overvoltage of graphitised carbon. Where pressures and temperatures are such that liquid chlorine is present, the ; foregoing effects of the chlorine adsorption on the carbon electrode overvoltage are more pronounced, and additionally, some instability is observed in the overpotentials of the graphitised carbon.
The foregoing observations and discussion has the following practical implications:
Firstly, in systems where the hydrochloric acid con-centration exceeds the constant boiling concentration (about 20 percent by weight, depending on the amount of disassociating additives such as titanium tetrachloride), graphitised carbon :
. X
- . . .: . . . .
. ,.. ~ ~ .. :
, : - ., - . :
., . - , 6~0 electrodes result in very high overvoltage inefficiencies and graphitised carbon electrodes are therefore much preferred. This preference extends also to carbon elec-trodes which have been catalyzed in the known manner with known catalysts such as the noble metals. For example, it has been found that platinized, ungraphitised carbon re-sults in much lower overvoltages than platinized, graphitised carbon~
Secondly, in systems where hydrogen storage is required, the storage can be accomplished by hydrogen adsorbtion into graphitised carbon. Such adsorptive storage of hydrogen in graphitised carbon has a great advantage over the known storage means, such as storage in iron-titanium hydride, for example, because it is not effected~by exposure to and contact with the hydrochloric acid electrolyte.
Thirdly, in systems where chlorine storage is required, for example, as liquid chlorine, safety and other advantages accrue from adsorbing the chlorine to ungraphitised carbon, with consequent modification in the pressure/temperature 2Q relationships controlling storage and release.
Fourthly, in systems where the hydrochloric acid concentration does not exceed the constant boiling concentra-tion but where the temperature~pressure relationship dictates the formation of liquid chlorine, graphitised carbon electrodes result in high and unstable overvoltages and, therefore, un-i graphitised carbon electrodes are much preferred.
~` The prolonged nitric acid treatment of carbon elec-trodes which results in sharp reduction of chlorine overvoltages, which has been referred to hereinbefore, does not change 3a but rather enhances all of the characteristic performances ' , : . "
~ 6~
which have been described above. For example, the adsorptive capacity of graphitised carbon for hydrogen chloride, of graphitised carbon for hydrogen, and of ungraphitised carbon for chlorine, are all greatly increased by the prolonged nitric acid treatment of the carbon electrodes The experimental data set forth above was obtained using Airco Speer (trademarkl Grade 37C ungraphitised carbon and Airco Speer (trademark) Grade 37G graphitised carbon, the latter being made by graphitising the former. Graphitising is the process of prolonged heating at very high temperatures in a controlled atmosphere. The very high temperatures are generally above 2,000C at which the carbon allotropic form is converted to the graphite allotropic form at practical rates. Substantially identical results to that achieved with the Airco Speer ~trade-mark~ material has also been obtained using Union Carbide Grade PG60 graphitised carbon and its ungraphitised counterpart.
The use of high HCl concentrations in HCl electro-chemical energy storage systems has generally been avoided because the electrodes are substantiàlly unstable in such a system. It has been found that the ungraphitised carbon electrodes, whether catalyzed or uncatalyzed are sufficiently stable to be of practical use in an aqueous HCl electrolyte of any concentration including concentrations when at least a portion of the HCl is not associated with the water.
Various changes and modifications can be made in the present invention without departing from the spirit and scope thereof. The various embodiments disclosed herein were for the purpose of further illustrating the invention ~' - .
.:. . -: . . . . .
6~
but were not intended to limit it. For example~ it will be recognized that the non-halogen electrode need not be a carbon electrode but can be any other known suitable material.
:: ~,''' ,. '- ,' ' :
: ~
Claims (11)
1. An HC1 electrochemical energy storage system comprising a cell having therein an aqueous hydrochloric acid electrolyte in which at least a portion of the HC1 is present in disassociated form and an electrode therein of ungraphitised carbon, and a non-halogen electrode, and communicating with said cell, means for storing hydrogen comprising graphitised carbon, and wherein said electrolyte contains a disassociating amount of an HC1 disassociating agent.
2. The electrochemical energy storage system of claim 1 wherein said electrolyte has an HC1 concentra-tion of at least about 20 percent.
3. The electrochemical energy storage system of claim 2 wherein said ungraphitised carbon electrode is a platinised ungraphitised carbon electrode.
4. The electrochemical storage system of claim 1 wherein said disassociating agent is titanium tetra-chloride.
5. The electrochemical energy storage system of claim 1 wherein said system contains means for storing chlorine comprising ungraphitised carbon communicating with said cell.
6. The electrochemical energy storage system of claim 1 wherein said carbon electrode has previously been subjected to prolonged contact with nitric acid.
7. An HC1 electrochemical energy storage system comprising a cell having therein an aqueous hydrochloric acid electrolyte in which at least a portion of the HC1 is present in disassociated form and at least one ungraphi-tised carbon electrode and a non-halogen electrode wherein said electrolyte contains an effective disassociating amount of a HC1 disassociated agent.
8. The electrochemical energy storage system of claim 7 wherein said agent is titanium tetrachloride.
9. An HC1 electrochemical energy storage system comprising a cell having therein an aqueous hydrochloric acid electrolyte in which at least a portion of the HC1 is present in disassociated form and an electrode therein of ungraphitised carbon and a non-halogen electrode, and communicating with said cell, means for storing chlorine comprising ungraphitised carbon, wherein said electrolyte contains a disassociating amount of an HC1 disassociating agent.
10. The electrochemical energy storage system of claim 9 wherein said electrolyte has an HC1 concentration of at least about 20%.
11. The electrochemical energy storage system of claim 9 wherein said disassociating agent is titanium tetrachloride.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US774,700 | 1977-03-04 | ||
| US05/774,700 US4124741A (en) | 1977-03-04 | 1977-03-04 | Hydrogen/chlorine electrochemical energy storage system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1108690A true CA1108690A (en) | 1981-09-08 |
Family
ID=25102003
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA298,189A Expired CA1108690A (en) | 1977-03-04 | 1978-03-03 | Hydrogen/chlorine electrochemical energy storage system |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4124741A (en) |
| JP (1) | JPS53109893A (en) |
| CA (1) | CA1108690A (en) |
| DE (1) | DE2808827C2 (en) |
| FR (1) | FR2382777A1 (en) |
| GB (1) | GB1600700A (en) |
| SE (1) | SE7801989L (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4273839A (en) * | 1979-07-30 | 1981-06-16 | Energy Development Associates, Inc. | Activating carbonaceous electrodes |
| US4251568A (en) * | 1979-08-27 | 1981-02-17 | Energy Development Associates, Inc. | Method of storing electrical energy |
| US4534833A (en) * | 1982-05-03 | 1985-08-13 | Energy Development Associates, Inc. | Zinc-chloride battery in a chlorine producing/consuming plant |
| DE3241801A1 (en) * | 1982-11-11 | 1984-05-17 | Siemens AG, 1000 Berlin und 8000 München | HYDROGEN / BROM CELL |
| US4497883A (en) * | 1983-04-29 | 1985-02-05 | Mobil Oil Corporation | Battery having cathode of sheet loaded with graphite and carbon sheet anode |
| US4882240A (en) * | 1985-08-02 | 1989-11-21 | The Boeing Company | Closed cycle electrical power system |
| US5219671A (en) * | 1985-12-04 | 1993-06-15 | Solar Reactor Technologies, Inc. | Hydrogen generation and utility load leveling system and the method therefor |
| US5443804A (en) * | 1985-12-04 | 1995-08-22 | Solar Reactor Technologies, Inc. | System for the manufacture of methanol and simultaneous abatement of emission of greenhouse gases |
| US7036616B1 (en) * | 1995-01-17 | 2006-05-02 | Electrion, Inc. | Hydrogen-electric hybrid vehicle construction |
| US20050211480A1 (en) * | 1995-01-17 | 2005-09-29 | Kejha Joseph B | Long range hydrogen fueled vehicle construction |
| GB0007306D0 (en) * | 2000-03-24 | 2000-05-17 | Scient Generics Ltd | Concept for a compact mixed-reactant fuel cell or battery |
| DE10196040D2 (en) * | 2001-02-15 | 2004-04-15 | Werner Henze | Device and method for converting heat and / or radiation energy into electrical energy |
| DE102007044171A1 (en) * | 2007-09-15 | 2009-03-19 | Bayer Materialscience Ag | Process for the production of graphite electrodes for electrolytic processes |
| DE102011056783A1 (en) | 2011-12-21 | 2013-06-27 | Rud Ketten Rieger & Dietz Gmbh U. Co. Kg | Driver for link chains of at least two sub-bodies and method for its preparation |
| EP2860814A4 (en) * | 2012-06-06 | 2015-10-28 | Dmitry Milanovich Tereshchenko | ELECTRIC ENERGY ACCUMULATION DEVICE COMPRISING AN ELECTRIC GAS BATTERY |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE380344A (en) * | ||||
| DE259241C (en) * | ||||
| DE26819C (en) * | K. W. ZENGER, k. k. Professor am böhmischen polytechnischen Institut in Prag | Regenerative accumulator | ||
| GB188665A (en) * | 1921-11-14 | 1923-10-18 | Naamlooze Venootschap Algemeen | Improvements in and relating to the compression, storage and treatment of gases |
| US1746542A (en) * | 1928-10-25 | 1930-02-11 | Westvaco Chlorine Products Inc | Manufacture of chlorine |
| US1847435A (en) * | 1930-01-27 | 1932-03-01 | Westvaco Chlorine Products Inc | Electrolytic manufacture of chlorine |
| BE481309A (en) * | 1947-03-25 | |||
| DE1596143A1 (en) * | 1965-07-01 | 1970-05-06 | Hoege Dipl Ing Hellmut | Method and arrangement for converting heat into electrical energy |
| DE1596153A1 (en) * | 1966-01-21 | 1971-01-07 | Hoege Dipl Ing Hellmut | Process for converting heat into electrical energy |
| US3772085A (en) * | 1971-11-18 | 1973-11-13 | Occidental Energy Dev Co | Method and apparatus for improving efficiency of high energy density batteries of metal-metal halide-halogen type by boundary layer |
-
1977
- 1977-03-04 US US05/774,700 patent/US4124741A/en not_active Expired - Lifetime
-
1978
- 1978-02-21 SE SE7801989A patent/SE7801989L/en unknown
- 1978-03-01 DE DE2808827A patent/DE2808827C2/en not_active Expired
- 1978-03-02 FR FR7805945A patent/FR2382777A1/en active Granted
- 1978-03-03 CA CA298,189A patent/CA1108690A/en not_active Expired
- 1978-03-03 JP JP2437078A patent/JPS53109893A/en active Pending
- 1978-03-06 GB GB8848/78A patent/GB1600700A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4124741A (en) | 1978-11-07 |
| GB1600700A (en) | 1981-10-21 |
| FR2382777A1 (en) | 1978-09-29 |
| FR2382777B1 (en) | 1982-04-16 |
| SE7801989L (en) | 1978-09-05 |
| JPS53109893A (en) | 1978-09-26 |
| DE2808827A1 (en) | 1978-09-07 |
| DE2808827C2 (en) | 1982-08-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 19980908 |