Enhanced alkaline water splitting on cobalt phosphide sites by 4d metal (Rh)-doping method

Abstract

The construction of effective water-splitting electrocatalysts in alkaline conditions is challenging due to lower water dissociation efficiency than in acidic conditions. In this study, we investigated the effect of doping 4d and 5d metals into the 3d metal active site of cobalt phosphide (CoxP) on the water-splitting reaction. Introducing Ru slightly improved hydrogen evolution efficiency, but Rh doping significantly enhanced the catalytic parameters with an overpotential of 0.03 V at 10 mA/cm2. Rh regulated the electronic structure of CoxP to improve proton reduction. The Rh-CoxP electrode showed a comparable catalytic efficiency to that of a Pt/C standard. Ir doping slightly improved catalytic reactivity, but not as much as Rh. Our results showed that doping 4d metal from the same group as Co maximizes the doping effect during hydrogen evolution. A lab-scale water electrolyzer built with Rh-CoxP successfully demonstrated catalytic water splitting in alkaline electrolyte.