Mixed oxides as oxygen electrodes. [NiOx, NiCo/sub 2/O/sub 4/, and RuO/sub 2/--TiO/sub 2/]

Conference · Wed Jan 01 04:00:00 EST 1975

OSTI ID:7364535

Singh, G; Miles, M H; Srinivasan, S

The irreversibility of the oxygen electrode reaction on metals and alloys is the main cause of efficiency losses in fuel cells, water electrolysis cells and some battery systems. Oxygen evolution always occurs on oxide covered surfaces while the reduction reaction generally takes place on bare metallic surfaces but can do so on oxides. Since the most likely candidates for reversible oxygen electrodes are oxides, mixed oxides or compound oxides, three types of oxides--NiO/sub x/, NiCo/sub 2/O/sub 4/ and RuO/sub 2/ parallel TiO/sub 2/ were examined as oxygen electrodes in KOH solution. When these oxide electrodes were prepared by thermal decomposition of their salts on a substrate, ratios of true to apparent surface areas of the electrodes were quite high (over 200) and the transfer coefficients, obtained from the Tafel lines for oxygen evolution in the temperature range 25--100/sup 0/C were 1.5 as compared with about half its value on nickel electrodes. Above 100/sup 0/C NiCo/sub 2/O/sub 4/ and RuO/sub 2/ parallel TiO/sub 2/ electrodes corroded in the strong (50 percent) KOH environment. Mixed oxides are more stable than simple oxides in the region of potential where oxygen reduction occurs. From the values of the Tafel slopes and exchange current densities for oxygen evolution and reduction on NiCo/sub 2/O/sub 4/ (a spinel) and RuO/sub 2/ parallel TiO/sub 2/, it is clear that reversibility of this electrode reaction was not obtained. Other mixed oxides (including spinels and perovskites) will have to be investigated with the aim of developing reversible oxygen electrodes.

• Research Organization: Brookhaven National Lab., Upton, N.Y. (USA)
• OSTI ID: 7364535
• Report Number(s): BNL-20984; CONF-751234-1
• Country of Publication: United States
• Language: English

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ALKALI METAL COMPOUNDS
CATALYSIS
CATALYSTS
CATHODES
CHALCOGENIDES
CHEMICAL REACTIONS
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COBALT OXIDES
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CRYOGENIC FLUIDS
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ELECTROCHEMICAL CELLS
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ELECTROLYSIS
ELECTROLYTIC CELLS
ELEMENTS
ENERGY STORAGE SYSTEMS
FABRICATION
FLUIDS
FUEL CELLS
HYDROGEN COMPOUNDS
HYDROXIDES
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METAL-GAS BATTERIES
NICKEL COMPOUNDS
NICKEL OXIDES
NONMETALS
OXIDES
OXYGEN
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