Transition-metal-oxide coated titanium electrodes for redox batteries
Abstract
The production of porous electrodes with reproducible surface activity for experiments to corroborate predictions of porous electrode theory to ascertain if simple one step outer sphere electron transfer mechanism applies to the ferric-ferrous redox reaction at high reactant/product concentrations in a strong acid chloride medium was investigated. Kinetic rate expressions of this couple under these conditions at the metal oxide surfaces were sought. Coatings of the conductive and active rutile structure form of selected transition metal oxides were desired. Both IrO2 and RuO2 coatings having the rutile structure were prepared by thermal decomposition of their respective hydrated chloride salts. Low over potential exchange current densities of the ferric-ferrous couple were measured in concentrated solution at Pt, RuO2 and IrO2 RDF's. Significant corrections were necessary for ohmic effects, mass transfer effects, and nonuniform current distribution. It is shown that the electrocatalytic activity of RuO2 is comparable to that of Pt while the activity of IrO2 is approximately an order of magnitude less than Pt. The measured free energy of activation was similar for all three substrates and a nonbinding interaction between the couple and the surfaces is suggested. The variation in exchange currents among the different substrates can be attributed to some extent on double layer effects but primarily to crystal structure differences.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- December 1982
- Bibcode:
- 1982STIN...8335287S
- Keywords:
-
- Catalysts;
- Chalcogenides;
- Electrocatalysts;
- Electron Transfer;
- Fuel Cells;
- Redox Cells;
- Electrochemical Cells;
- Energy Conversion;
- Fabrication;
- Iridium Isotopes;
- Iron Compounds;
- Ruthenium Compounds;
- Transition Metals;
- Electronics and Electrical Engineering