Plasma Etching of Pyrite-Type Nickel Diselenide Nanosheets to Create Selenium Vacancies for Applications as Electrocatalysts for Hydrogen Evolution

Boosting the hydrogen evolution reaction (HER) process with highly efficient non-noble metal catalysts is crucial for hydrogen-powered fuel cells. Pyrite-type NiSe 2 is one of the most promising HER catalysts due to its inexpensive cost and good conductivity, although its intrinsic activity is moderate. Using a plasma etching method on a carbon cloth substrate material, we created a large number of selenium vacancies on NiSe 2 nanosheets (NiSe 2 -V Se /CC). With a low overpotential of 91 mV and a Tafel slope of 91 mV dec –1 at 10 mA cm –2, as well as a durability of 20 h at high current (100 mA cm –2 ), the NiSe 2 -V Se /CC demonstrates superior HER performance for its catalytic activity and long-term stability. Cross-validated by measurement analyses and density functional theory calculations, the introduction of vacancies reduces the resistivity of NiSe 2 and optimizes its hydrogen adsorption energy ( G H* ) and water adsorption energy ( G H2O* ). Based on defect engineering, this study proposes an approach to designing improved electrocatalysts for alkaline HER.