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)/CoS electrocatalysts for full water splitting. A CoP/CoS hybrid was prepared for the first time by partial homogeneous transformation of in situ-formed CoS, in which the atomic heterointerface was formed between CoP and CoS. Systematic experiments and theoretical calculations confirm that the as-formed atomic heterointerface can induce local charge distribution in CoP/CoS, which can not only accelerate the charge transfer but also optimize the hydrogen adsorption energy of CoP in favor of the fast transformation of H into H. Meanwhile, the CoS component can also increase the water adsorption capability of CoP/CoS. Benefiting from these outstanding advantages, an alkaline electrolyzer based on CoP/CoS as both electrodes achieves a low cell voltage of 1.6 V at an operating current density of 10 mA cm, and at the same time, it can also be self-powered by a home-assembled Zn-air battery employing the same CoP/CoS 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.