HYDROGEN OVERPOTENTIAL FOR INTERMETALLIC COMPOUNDS, TIAL, FEAL AND NIAL, CONTAINING 3D TRANSITION-METALS

A theory proposed for understanding the alloying effect on the hydroge n; overpotential of alloys has been further confirmed in the present s tudy of intermetallic compounds, TiAl, FeAl and NiAl containing variou s 3d transition elements. The trend of hydrogen overpotential changes with alloying elements in these compounds resembled the observation in Ti-, Fe- and Ni-based binary alloys. The variation in hydrogen overpo tential was explained in terms of the direction for the charge transfe r between atoms as is shown in the transition metal based binary alloy s. In other words, the most negatively charged atom in the compound, a s the result of charge transfer between the constituent atoms, is resp onsible mainly for the hydrogen overpotential change with alloying. Th is concept was also applicable to the hydrogen overpotential problem f or transition metal based ternary alloys.