engleski

The electronic structure of the α–Ni(OH)2 films: Influence on the production of the high– performance Ni–catalyst surface

In a view of the importance of the solid-state properties of the oxide/hydroxide films on the efficiency of Ni-catalysts, this work is focused on the electronic structure of the passive α- Ni(OH)2 film that behaves as an n-type semiconductor (with anion vacancies as dominant point defects). The solid-state transformation of the n-type α- Ni(OH)2 film to Ni was discussed in the terms of Gerischer’s approach for a reductive decomposition of a classical semiconductor. The kinetics of the α-Ni(OH)2 decomposition to Ni was studied in situ and the decomposition mechanism was proposed. The nickel metal nucleation begins at the anion vacancies on the film|solution interface and finally the whole oxide film matrix transforms to the new metallic phase. The hydrogen evolution reaction (h.e.r.) takes place at a potential more positive than Er(H2/H+) at a freshly, in situ extracted Ni surface. The semiconducting properties of the passive film were compared to those of an oxide film, also n- type semiconductor that is formed on Ni by ion- implantation method. The latter film mentioned shows compact, more ordered and less amorphous structure than the first one what is in accordance to the X-ray photoelectron spectroscopy (XPS) results.

nickel-catalyst; n–type α–Ni(OH)2 film; Ni nucleation; hydrogen evolution reaction

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