Enhancement of HER kinetics with RhNiFe for high-rate water electrolysis

Abstract

The revolutionary findings of new catalysts with exceptional activities for electrocatalytic water splitting are unavoidable for viable hydrogen production. Herein, nanosheets of NiFeCHH (nickel iron carbonate hydroxide hydrate) showed commanding oxygen evolution reaction (OER) and with the introduction of Rh³⁺ ions showed humongous hydrogen evolution reaction (HER) in 1 M KOH for the first time. This new idea of introducing Rh³⁺ ions into NiFe systems to form trimetallic RhNiFe carbonate hydroxide systems has shown overwhelming HER response, and hence, the overall voltage for alkaline water splitting is much reduced. The overpotential required at 50 mA cm⁻² for OERs was around 207 mV for NiFeCHH (1 : 0.5) with a Tafel slope value of 30 mV dec⁻¹. The Rh³⁺–NiFeCHH (1 : 0.5) for HERs showed an overpotential of 36 mV at 50 mA cm⁻² with a Tafel slope value of 34 mV dec⁻¹. NiFeCHH (1 : 0.5) and Rh³⁺–NiFeCHH (1 : 0.5) used as the anode and cathode, respectively, showed an overpotential of 286 mV at 50 mA cm⁻² with utmost stability. This finding of adding Rh³⁺ ions to form RhNiFe electrodes can have huge advantage for alkaline water electrolysis with lesser energy applied.