ELECTROCATALYTIC PERFORMANCE OF COMPOSITE-COATED ELECTRODES FOR ALKALINE WATER ELECTROLYSIS

Raney Ni, Raney Ni-Co and Raney Co composite-coated electrodes were investigated for hydrogen evolution cathodes and oxygen evolution anodes in alkaline media. The influence of the temperature, the OH- ion concentration and potential cycling on the kinetics of the hydrogen evolution reaction (HER) was investigated. The HER reaction mechanisms depends on the KOH concentration, since the latter strongly influences the Tafel slope while the apparent energy of activation is 8.4 kJ mole-1. Potential cycling is detrimental to the HER and eventually causes cracks in the electrode material. The presence of Co in the electrode material is also detrimental to the HER. The best performances with respect to the oxygen evolution reaction (OER) were observed for Raney Ni composite electrodes whose i0 is ≈ 100 times higher than for materials containing Co. The apparent energy of activation of the OER on Raney Ni composite electrodes is 12.2 kJ mole-1 and the Tafel slope is equal to 80 mV between 54 and 69°C in 32 ω/o KOH. © 1990.