Three-dimensional nano-framework CoP/Co2P/Co3O4 heterojunction as a trifunctional electrocatalyst for metal–air battery and water splitting

Abstract

Clean renewable energy conversion and storage technologies, such as metal–air batteries, water splitting and fuel cells, require the development of cost-effective trifunctional electrocatalysts toward the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Herein, a three-dimensional (3D), heterogeneous nano-architecture composed of a mixture of CoP, Co₂P, and Co₃O₄ is fabricated via LiCl-assisted thermal phosphidation of porous Co₃O₄. Thanks to the combination of heterojunction and 3D nano-network which facilitates the mass/charge transport and the spatial redistribution of electron, the resultant electrocatalyst exhibits prominent activities toward the ORR, OER and HER, surpassing most of the previously reported trifunctional electrocatalysts. Notably, the Zn–air battery with CoP/Co₂P/Co₃O₄ as the air cathode exhibits superior efficiency and durability, comparable to those of the apparatus based on the state-of-the-art Pt/C//RuO₂. Moreover, the electrolyzer using CoP/Co₂P/Co₃O₄ as both the anodic and cathodic electrodes, requires a potential as low as ∼1.87 V to drive a current density of 200 mA cm⁻² for overall water splitting. This well-defined nano-heterogeneous network-based catalyst can offer some interesting prospects for the design concept of outstanding multifunctional catalysts toward various energy conversion and storage devices.