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)/Co ₉ S ₈ electrocatalysts for full water splitting. A CoP/Co ₉ S ₈ hybrid was prepared for the first time by partial homogeneous transformation of in situ-formed Co ₉ S ₈ , in which the atomic heterointerface was formed between CoP and Co ₉ S ₈ . Systematic experiments and theoretical calculations confirm that the as-formed atomic heterointerface can induce local charge distribution in CoP/Co ₉ S ₈ , 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 _ads into H ₂ . Meanwhile, the Co ₉ S ₈ component can also increase the water adsorption capability of CoP/Co ₉ S ₈ . Benefiting from these outstanding advantages, an alkaline electrolyzer based on CoP/Co ₉ S ₈ 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/Co ₉ S ₈ 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.