Electrocatalysts For Alkaline Water Electrolysis Research Articles

Ni-base amorphous alloys as electrocatalysts for alkaline water electrolysis

The development of efficient and cost effective electrodes for hydrogen generation from water electrolysis and for hydrogen oxidation in power generation from fuel cells is very important in developing the hydrogen economy. This paper focuses on the role of the structure and chemistry of amorphous metal alloys (AMA) on the electrocatalytic activity for the hydrogen evolution reaction (HER) in alkaline water electrolysis. The test AMA electrodes, Ni-base alloys with different metal additive ratios, were prepared by a planar flow casting technique. The electrochemical behaviour of the AMA was investigated in 1 M KOH at 30 °C by cyclic voltammetry and steady-state polarization techniques. The AMA displayed voltammetric responses similar to that of crystalline Ni, however, differences were found in the oxide formation mechanism. The electrocatalytic activities of the AMA were dependent on the AMA composition. The prepared alloys displayed good stability relative to that of crystalline Ni. Even after extensive potential cycling which roughened and attacked the crystalline Ni electrodes, the surfaces of the amorphous alloys remained smooth. As a result of the roughening of the crystalline Ni electrodes, the amorphous alloys appeared to be less active than crystalline Ni for the HER on the basis of geometric surface area.

Surface microstructure on Raney nickel catalysts

Raney nickel is a favorite electrocatalyst for alkaline water electrolysis and fuel cells. The good electrochemical properties of this material result from its very fine porosity giving the electrodes a large effective surface. Usually the microstructure is formed by chemical etching of a nickel alloy, leaving back a highly porous electrode consisting of nearly pure nickel. It is well known that the total effective surface can considerably vary depending on the etching process, but up to now the understanding of the influence of all etching parameters on the resulting pore structure is quite ambiguous. Consequently, the study of the microporosity on Raney nickel is an important task within the scope of the development of electrocatalytic electrodes.

Materials research and development of electrocatalysts for alkaline water electrolysis

Preparation, properties and long term performance of spongy Raney nickel type electrocatalysts for cathodic H 2 evolution show that secondary structure (fine pores) and tertiary structure (coarse pores and cracks) of this catalyst depend on the chosen preparation procedure and that they influence the effective catalytic activity sizeably. Long term performance is remarkably improved by controlled leaching of the Raney-nickel precursor and oxidative aging of the developed Raney-metal matrix. Porous oxygen evolving anodes containing metallic cobalt and nickel are prepared by reductive sintering and the effect of chemical composition on catalytic activity is reported. It is still impossible to combine highest activities with technically sufficient longevity of this type of activated anodes.