Engineering Selenium Vacancies on CoSe₂ Nanoarrays for Alkaline Hydrogen Evolution

The development of highly efficient nonnoble metals toward hydrogen evolution reaction (HER) electrocatalysts is significant for producing hydrogen via water electrolysis. Selenides are becoming increasingly attractive owing to their excellent HER activity. Herein, CoSe 2 nanorods were successfully manufactured on a carbon cloth (CC) and selenium vacancies were obtained using a plasma cleaner (CoSe 2 -V Se /CC) to enhance their intrinsic catalytic activity. The synthetic catalyst exhibited a lower overpotential of 88 mV at 10 mA cm –2 in 1 M KOH and high durability over 100 h at 100 mA cm –2, which can be ascribed to the increased electrochemical surface area and rapid electron transfer. In addition, density functional theory (DFT) calculations showed that introducing Se vacancies optimized the hydrogen adsorption energy on the Se site and reduced the transition-state energy barrier of water dissociation. This study laid a firm foundation for preparing high-performance and stable electrocatalysts via anion defect engineering.