Heterostructure of Semiconductors on Self-Supported Cuprous Phosphide Nanowires for Enhanced Overall Water Splitting

Rational design, controllable synthesis, and an in-depth mechanism study of Cu-based bifunctional semiconductor heterostructures toward overall water splitting (OWS) are imperative but still face challenges. Herein, n-type iron oxide and p-type nickel phosphide and cobalt phosphide are respectively coupled with p-type cuprous phosphide nanowires on Cu foams via a general growth-phosphorization strategy. These self-supported semiconductor heterojunctions with different built-in potentials ( E BI ) are used as binder-free electrodes for OWS and exhibit significantly improved electrocatalytic activities compared to their counterparts. Among them, the heterostructure with the largest E BI of 1.57 V attains the smallest overpotential of 97 mV at 10 mA cm –2 for the hydrogen evolution reaction and 243 mV at 50 mA cm –2 for the oxygen evolution reaction in 1 M KOH. The corresponding two-electrode electrolyzer requires a cell voltage of 1.685 V at 50 mA cm –2 and shows admirable long-term stability at 100 mA cm –2 with a Faraday efficiency of around 98%. These promoted electrocatalytic performances originate from the enhanced active site, accelerated charge transfer, enlarged electrochemical active surface area, and synergy between different components at the heterointerface. This work represents a promising avenue to construct cost-efficient semiconductor heterostructures as bifunctional electrocatalysts applied to the sustainable energy industry.