Atomic Heterointerface-Induced Local Charge Distribution and Enhanced Water Adsorption Behavior in a Cobalt Phosphide Electrocatalyst for Self-Powered Highly Efficient Overall Water Splitting

Developing economical and highly efficient noble metal-free electrocatalysts for overall water splitting is an essential precondition for renewable energy conversion. Herein, we highlight atomic heterointerface engineering in constructing highly efficient cobalt phosphide (CoP)/Co9S8 electrocatalysts for full water splitting. A CoP/Co9S8 hybrid was prepared for the first time by partial homogeneous transformation of in situ-formed Co9S8, in which the atomic heterointerface was formed between CoP and Co9S8. Systematic experiments and theoretical calculations confirm that the as-formed atomic heterointerface can induce local charge distribution in CoP/Co9S8, which can not only accelerate the charge transfer but also optimize the hydrogen adsorption energy of CoP in favor of the fast transformation of Hads into H2. Meanwhile, the Co9S8 component can also increase the water adsorption capability of CoP/Co9S8. Benefiting from these outstanding advantages, an alkaline electrolyzer based on CoP/Co9S8 as both electrodes achieves a low cell voltage of 1.6 V at an operating current density of 10 mA cm–2, and at the same time, it can also be self-powered by a home-assembled Zn–air battery employing the same CoP/Co9S8 as the air electrode for prospectively achieving renewable energy conversion. This work demonstrates the importance of heterostructure engineering in developing noble metal-free catalysts for high-performance water electrolysis.