Activating CoP via spontaneous atomic palladium doping for efficient hydrogen evolution

Electrocatalytic hydrogen evolution is an efficient and clean hydrogen production technology with simple process and high product purity. Searching for inexpensive alternatives to platinum will help popularize proton exchange membrane water electrolysis (PEMWE) technology. However, the alternative catalytic materials are essentially limited by low catalytic efficiency. Herein, we address this challenge through chemically activating cobalt phosphide (CoP) by doping a small amount of atomic palladium. Palladium substitution occurs at the cobalt site of CoP. Theoretical calculations manifest that the phosphorus atoms near the palladium sites exhibit almost zero hydrogen adsorption free energy. The final cobalt phosphide doped with only 2 wt% of palladium shows wonderful HER performance. Specifically, its overpotential at a current density of 10 mA cm-2 is only 37.5 mV in an acidic medium, and the corresponding Tafel slope is 56 mV dec- 1. This work provides a reference for preparing high performance non-platinum catalysts.