Engineering sulfur vacancies into Fe₉S₁₀ nanosheet arrays for efficient alkaline hydrogen evolution

The development of Earth-abundant transition metal sulfide electrocatalysts with excellent activity and stability toward the alkaline hydrogen evolution reaction (HER) is critical but challenging. Iron-based sulfides are favored due to their economic benefits and good stability, but their intrinsic catalytic activity still needs to be improved urgently. Herein, we successfully prepared Fe₉S₁₀ nanosheet arrays on iron foam (Fe₉S₁₀/IF) through a simple one-step method and utilized plasma treatment to introduce S vacancies (Fe₉S₁₀-V_s/IF) to regulate their intrinsic catalytic activity. The final materials demonstrate excellent HER performance, and only need 149 mV to drive a current density of 10 mA cm^-2 and a small Tafel slope of 50 mV dec^-1. The experimental results show that the existence of S vacancies can enhance their intrinsic electrocatalytic activity. This work provides a reference value for the future regulation of iron-based sulfides and is devoted to the development of non-precious metal catalysts toward the HER.