The influence of local structure of nanocrystalline Ni films on the catalytic activity

The aim of our investigation was to study the influence of the nanoparticles size (the local structure) in sputter deposited Ni films on hydrogen evolution kinetics. The grain size of Ni-particles (11–100 nm) was controlled by the substrate temperature (from 35 °C to 300 °C). The dependence of the kinetic parameters on the temperature at which the films were deposited was measured in alkaline solution by electrochemical impedance spectroscopy (EIS). It correlates well with the change of the ratio between the nanocrystalline and non-homogenous disordered fraction of the nc-Ni film observable by Grazing incidence small angle X-ray scattering (GISAXS) analysis and ascribed to the intercrystalline matter. The catalytic activity of nanocrystalline nickel (nc-Ni) on the hydrogen evolution reaction (h.e.r.) is markedly greater at larger fraction of the spherical inhomogeneities inside the film. This effect is especially strongly pronounced for the nc-Ni films prepared on the substrates at lower temperatures.