Copper phosphosulfides as a highly active and stable photocatalyst for hydrogen evolution reaction

Transition-metal phosphosulfides (TMPSs) have recently shown outstanding electrocatalytic performances toward hydrogen evolution reaction (HER), superior to the sulfide and phosphide counterparts. However, there are only limited TMPSs available due to the synthetic challenge. Herein, we demonstrate a novel synthetic approach for copper phosphosulfide (CuPS) and the first application in photocatalytic HER. Based on the thermodynamic considerations of starting materials, two synthetic routes are designed to obtain two distinct crystal structures (CuS|P and Cu₃P|S). Dramatically enhanced photocatalytic HER activities are achieved for both Cu₃P|S (2,085 μmol g^-1 h^-1) and CuS|P (976 μmol g^-1 h^-1) without using co-catalysts. First-principles calculations unveil the underlying mechanism for the improved HER activity, in which the Gibbs free energy of hydrogen adsorption approaches close to 0 eV and the number of active sites considerably increases with the formation of CuPS structure. This work provides new insight and design principle on preparing TMPSs for high-performance energy conversion applications.