ELECTRODEPOSITED Ni-Fe-C CATHODES FOR HYDROGEN EVOLUTION

摘要

Tailoring of active nickel alloy cathodes for hydrogen evolution in a hot concentrated hydroxide solution was attempted by electrodeposition. Electrodeposited iron is naturally more active for hydrogen evolution than nickel, but Ni-Fe alloys show further high activity for hydrogen evolution, although the rate-determining step being assumed as proton discharge is not changed. The carbon addition to iron or nickel remarkably enhances the activity for hydrogen evolution and changes the mechanism of hydrogen evolution. Ternary Ni-Fe-C alloys show the highest activity for hydrogen evolution, and the Tafel slope of hydrogen evolution is about 30 mV/decade, suggesting the rate-determining step of desorption of adsorbed hydrogen by recombination. XPS analysis reveals that the charge transfer occurs from nickel to iron in alloys and the carbon addition particularly enhances the charge transfer. Accelerated proton discharge due to enhanced charge transfer from nickel to iron is responsible for the high activity of the Ni-Fe-C alloys for hydrogen evolution.