Nitrogen-driven electronic modulation and long-term durability of AlCoCrFeNiN high entropy alloy thin films for...

High entropy alloys (HEAs) are attracting increasing attention as electrocatalysts due to their structural robustness and tunable surface chemistry; however, sustaining high performance in corrosive environments remains a major challenge. In this study, AlCoCrFeNiN HEA thin films were fabricated via direct current magnetron sputtering, and the effects of nitrogen doping on oxygen evolution reaction (OER) activity and long-term stability were systematically investigated in alkaline-saline electrolyte (1.0 M KOH + 3.5 wt% NaCl). Nitrogen incorporation significantly improved corrosion resistance and catalytic durability, with the optimized film (HEAN20, 28.7 at.% N) maintaining high OER activity for over 300 h of continuous operation. This film achieved a low overpotential of 399 mV and a Tafel slope of 114.3 mV·dec^-1 at 100 mA·cm^-2, along with the highest double-layer capacitance (Cdl = 2.03 mF·cm^-2) among the tested samples. Density functional theory calculations revealed that nitrogen doping tailors the electronic configuration, facilitates charge redistribution, and optimizes the adsorption of OER intermediates. These findings provide mechanistic insight into the role of nitrogen in stabilizing HEA catalysts and demonstrate a viable strategy for developing durable, efficient, and noble-metal-free electrodes for water splitting in harsh environments.