Abstract
The electromotive force (EMF) of H2|H+|M cell (M=transition metals and s-p metals) was measured as a function of temperature. From the measurement, the thermodynamic quantities of hydrogen-metal systems at infinite dilution limit, Δ\barGH, Δ\barSH, and Δ\barHH, were obtained. These values for Ti, V, Nb and Ta (i.e. the exothermic system) were basically in agreement with the values derived from solubility data, respectively. While, in the case of the endothermic system (i.e. Mo, W, Co, Rh, Ir and Pt), the thermodynamic values measured by the EMF method, for instance, Δ\barH<0, were different from those of the solubility data. From these systematic measurements, the thermodynamic quantities obtained by the EMF method were discussed on the basis of the bonding nature of metal-hydrogen systems by considering the chemisorption of hydrogen on the metal surface.
