Rational design of self-supported WC/Co3W3N/Co@NC yolk/shell nitrogen-doped porous carbon catalyst for highly efficient overall water splitting

Abstract

Designing high-efficiency catalysts with earth-abundance elements for overall water splitting (OWS) in alkaline electrolyte has been unsettled owing to the non-negligible overpotential of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). An electrocatalyst with decent HER and OER activities in the same electrolyte is crucial for sustainable energy storage and conversion device. In this work, a nitrogen-doped porous carbon confined yolk/shell OWS catalyst of WC/Co3W3N/Co@NC has been prepared via calcination polyhedron encapsulation structure PW12 @ZIF-8 @ZIF-67 generated by the epitaxial method. Because of the optimized chemical composition, the derived WC/Co3W3N/Co@NC multisite catalyst has outstanding OWS performance in 1 M KOH solution. For example, to reach a current density of 10 mA cm-2, it only needs low overpotentials of 141 and 280 mV for the HER and OER, respectively. By using the easy operation and classical bubble extraction method, we find that the Faraday efficiencies of the catalyst for HER and OER are 94.3% and 97.4%, respectively. Moreover, taking advantage of the micropores and mesopores in the yolk/shell structure, it exhibits enhanced stability and promoted diffusion kinetics. This work initiates an effortless approach to the synthesis of the highly efficient yolk/shell carbon-based OWS electrocatalyst.