Br-Induced d-Band Regulation on Superhydrophilic Isostructural Cobalt Phosphide for Efficient Overall Water Splitting

Abstract

Highly efficient novel electrocatalysts for hydrogen/oxygen production are urgently required, for noble metal-based catalysts substitution. Cobalt phosphides have shown great potential for serving as bifunctional catalysts, owing to the cost effectiveness and high conductivity. However, the water splitting ability of them is still not comparative with commercial noble counterparts. In this work, we reported a Br-induced strategy, to obtain an ultra-hydrophilic isostructural Br_0.036─Co_1.085P@NF catalyst by a gas-solid reaction method. As a typical halogen element, the introduction of Br can greatly enhance the surficial hydrophilicity and thus further impart ideal adsorption ability for water molecules. Meanwhile, the electronic structure could be regulated to further induce the generation of isostructural cobalt phosphides (CoP/Co₂P). As a result, the contact angle of Br_0.036─Co_1.085P@NF catalysts nearly cannot be caught owing to the ultra-hydrophilicity. It is also confirmed that, the d-band center of Co shows apparent negative shift after Br introduction, which reduces the adsorption energy of oxygen-containing intermediates thereby facilitating the desorption process. Besides, the introduction of Br can also reduce the barrier of O₂ formation, show more favorable dynamic behaviors. This work proved the accessibility for an effective design strategy on halogen-induced isostructural transition metal phosphides catalysts for high-performance overall water splitting.