A simple surface phosphating treatment accompanied by the formation of Co-based multiphase heterostructure for efficient oxygen evolution reaction

Abstract

Constructing heterostructures to increase the conductivity and enhance reaction kinetics of Co-based oxides is a fascinating yet challenging method for creating effective catalysts for oxygen evolution reaction. The controlled synthesis of multi-phase heterostructures comprising identical elements has been rarely reported in the literature. Herein, a simple and scalable strategy is proposed to prepare a multi-phase heterostructure of Co3O4 and CoO through an efficient hydrogen reduction assisted strategy and subsequent surface phosphating treatment. In the process of effectively doping phosphorus (P) atoms, spinel-type Co3O4 and rock-salt type CoO heterojunctions are cleverly formed, and an abundance of oxygen defects are also introduced. The spontaneous integration of multi-phase heterostructure of well-crystallized Co elements as well as the incorporation of P on catalyst surface, not only alters the electronic structure to foster the activation of oxygen and the disaggregation of water, but also causes a synergistic effect at the interface. Benefiting from these characteristics, the hybrid catalyst surpasses the RuO2 benchmark with outstanding OER performance, reaching 10 mA cm−2 at only 299 mV overpotential and excellent stability in alkaline electrolyte.