Electrodeposited Ni-Sn coatings as electrocatalysts for hydrogen and oxygen evolution in alkaline solutions

Abstract

The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) were studied at electrodeposited Ni-Sn alloys. All coatings were electrodeposited onto a Ni 40 mesh substrate from a bath containing Ni and Sn ions in the presence of pyrophosphate and glycine. The electrodes were investigated by cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electrochemical impedance spectroscopy (EIS) and polarization measurements. It was shown that among the increase of the roughness factor of Ni- Sn coatings with the increase of electrodeposition current density, their composition was also responsible for their catalytic activity for both, the HER and the OER. In the potential range of the HER two regions were observed, but none of them was characterized with the linear dependence E vs. log j (Tafel slope). For the OER two Tafel slopes were detected: one of about 60 mV dec-1 at lower current densities (up to about 20 mA cm-2) and one of about 120 mV dec-1 at higher current densities. Based on the Tafel slopes and EIS results the mechanisms for the HER and OER were proposed and discussed.