Effect of Sputtering Power on the Structure and Electrocatalytic Hydrogen Evolution Performance of Mo₂N Thin Films

Mo₂N thin films were successfully prepared using a magnetron sputtering deposition system. The effects of sputtering power on the microstructure, crystal structure, and electrocatalytic hydrogen evolution performance of the Mo₂N films were systematically investigated. The results showed that at a sputtering power of 200 W, the Mo₂N film exhibits a relatively rough surface morphology, with preferential grain growth along the (111) crystal plane and an optical bandgap of 1.09 eV. In 1.0 M KOH alkaline medium, the overpotential and Tafel slope were as low as 169 mV and 146 mV·dec⁻¹, respectively. In 0.5 M H₂SO₄ acidic medium, the corresponding values were 187 mV and 151 mV·dec⁻¹. Further analysis revealed that moderate sputtering power facilitates the formation of a microstructure with high defect density, which provides additional active sites. The (111) crystal plane plays a significant role in modulating the electronic structure of the Mo₂N film, shifting the d-band center of Mo atoms to a moderate position, thereby optimizing the adsorption and desorption of H^* on the active sites and effectively enhancing the electrocatalytic hydrogen evolution performance. This study provides new insights for the fabrication of efficient and stable non-noble-metal electrocatalysts.