Galvanic displacement of Co with Rh boosts hydrogen and oxygen evolution reactions in alkaline media

Abstract

Abstract The growing energy crisis put an emphasis on the development of novel efficient energy conversion and storage systems. Here we show that surface modification of cobalt by a fast galvanic displacement with rhodium significantly affects the activity towards hydrogen (HER) and oxygen evolution (OER) in alkaline media. After only 20 seconds of galvanic displacement, the HER overpotential is reduced by 0.16 V and OER overpotential by 0.06 V. This reduces the predicted water splitting voltage from 2.03 V (clean Co anode and cathode) to 1.81 V at 10 mA cm− 2. During the galvanic displacement process, the surface roughness of the Co electrode does not suffer significant changes, which suggests an increase in the intrinsic catalytic activity. Density Functional Theory calculations suggest that the reactivity of the Rh-modified Co(0001) surface is modified compared to the clean one. In the case of HER, experimentally observed activity improvements are directly correlated to the weakening of the hydrogen-surface bond, confirming the beneficial role of Rh incorporation into the Co surface.