Local Structure of Pulse Plated Ni Rich Ni-Zn Alloys and Its Effect on the Electrocatalytic Activity in the Hydrogen Evolution Reaction

Ni rich NiZn alloys were prepared on Pt substrates by galvanostatic pulse plating from baths of variable Ni:Zn ratio. The pulse plated NiZn alloys are crystallographically amorphous and their overall chemical composition shows relatively weak dependence on the pulse plating conditions. The local structure of the NiZn alloys determined from EXAFS spectra conforms to a model assuming coexistence of cubic and hexagonal-like arrangements. In the case of alloys plated from baths of low Zn content the cubic environment is zinc free and in the case of alloys plated from bath of high Zn content the Zn enters both cubic and hexagonal arrangement. The fraction of each of the coexisting local structures reflects the pulse plating conditions. The Ni rich NiZn alloys are active in the hydrogen evolution reaction showing electrocatalytic activity superior to that of bulk nickel. The electrocatalytic activity of the alloy samples in hydrogen evolution increases with increasing fraction of hexagonal local structure. This behavior is attributed to the residual strain mainly in the hexagonal-like environment.