Janus CoN/Co cocatalyst in porous N-doped carbon: toward enhanced catalytic activity for hydrogen evolution

Abstract

Using earth abundant transition metal-based compounds to replace noble metal catalysts towards hydrogen evolution from water splitting seems to have great importance worldwide. Compositional modulation and structural design on nanoscale have been hot topics for the optimization of their catalytic properties and have attracted great research interest. In this study, we report Co/CoN Janus nanoparticles embedded in a porous nitrogen doped carbon (Co/CoN–NC) composite catalyst, derived by the heat treatment of a Co²⁺ containing polymer in ammonia atmosphere. The as-obtained hybrid catalyst showed excellent electrocatalytic activities for the hydrogen evolution reaction in both acidic and basic media, and it delivered a current density of 10 mA cm⁻² at the overpotential of 160 mV in 1 M KOH and 190 mV in 0.5 M H₂SO₄ electrolyte. In addition, the catalyst could sustain potentiostatic electrolysis for at least 100 hours at 10 mA cm⁻² in both acidic and alkaline solutions. Mechanistic study suggested that the high activity of the composite electrocatalyst originated from the Janus effects between Co and CoN, which enhanced the electron transfer efficiency and led to fast hydrogen adsorption and desorption kinetics.