RELATION BETWEEN NICKEL CRYSTALLINE-STRUCTURES AND THEIR ELECTROCATALYTIC PROPERTIES .2. DETERMINATION OF THE NATURE OF ADSORPTION SITES FOR HYDROGEN

It is possible to determine the function Q=f(E) which indicates for each potential value, the equilibrium-state hydrogen coverage. By preliminary determination of the electrode roughness from the differential capacity obtained by pulse techniques the maximum coverage of weakly bound Hads can be deduced. By assuming that each Hads atom corresponds to one site, the number of sites per unit area of the interface is calculated. Besides, for electrodes characterized by different crystallite diameters, the number of atoms located in different positions (edges, crystallite faces, etc.) may be determined. By comparison of the theoretical estimate with the number of sites which can bind Hads, it can be concluded that the sites are defined only by the low coordination Ni atoms (crystallite edges and summits). © 1979 Elsevier Sequoia S.A.