Temperature dependence of electrocatalytic behaviour of some glassy transition metal alloys for cathodic hydrogen evolution in water electrolysis

Abstract

A series of glassy transition metal alloys of various compositions, involving the elements Ni, Mo, V, Fe, Cr, Ti, together with B, have been investigated as electrocatalysts for the cathodic evolution of hydrogen. The polarization behaviour over a range of temperatures has been evaluated and exchange current-densities, Tafel slopes and apparent heats of activation have been determined. The Tafel slope behaviour as a function of temperature has been analysed to give the formal enthalpic ( α H) and entropic ( α S) components of the transfer coefficient or, for certain conditions, the barrier symmetry factor for charge transfer. Potential-relaxation experiments, following interruption of cathodic polarization currents, enable the pseudocapacitance, C φ , for H adsorption to be evaluated as a function of overpotential, η. Integration of the C φ vs η relation for one of the NiMo based alloys suggests that cathodic H 2 evolution takes place through proton discharge on to a surface substantially covered by H, a factor that is related to the tendency for some of these glassy metals to form hydride phases during H 2 generation.