Plasma Transforming Ni(OH)₂ Nanosheets into Porous Nickel Nitride Sheets for Alkaline Hydrogen Evolution

Nickel nitride (Ni₃N) is a superior hydrogen evolution reaction (HER) catalyst where the nitrogen source is usually ammonia and the reaction temperature is high during the synthesis process. Herein, we employed an innovative method to obtain three-dimensional porous nickel nitride nanosheets on Ni foam (Ni₃N/NF) by transforming Ni(OH)₂ nanosheets in N₂-H₂ glow discharge plasma. The obtained Ni₃N/NF displays a high HER activity with a small overpotential of 44 mV and a low Tafel slope of 46 mV dec^-1, which is competitive to a Pt/C catalyst. Both the test data and simulation results prove that active ions and radicals in plasma play essential roles in achieving the facile nitridation, as well as building a nanostructured morphology over the Ni₃N/NF surface. The unique synthesis method opens new avenues for metal nitrides of HER catalysts and beyond.