DC Magnetron Sputtering for Synthesizing Bimetallic NiFe Thin Films as Efficient OER-Catalyzing Electrodes.

Industrial water electrolysis systems for hydrogen production use noble metal-based RuO2/IrO2 to catalyze the oxygen evolution reaction (OER). Replacing noble metal compounds with earth-abundant NiFe compounds requires a scalable synthesis technique with structural and morphological control. In this study, DC magnetron sputtering was systematically investigated as a scalable approach for synthesizing NiFe bimetallic thin-film electrocatalysts as alternatives to noble metal-based materials. NiFe thin films (~200 nm) with varying Fe contents were deposited on SS-316L substrates and characterized using compositional, morphological, structural, and electrochemical techniques. Scanning electron microscopy revealed a columnar morphology, while X-ray diffraction confirmed the formation of a NiFe random solid solution. The Fe ratio was found to strongly influence OER performance, with the Fe24Ni76 composition exhibiting the best activity, requiring an overpotential of 361 mV vs. RHE to achieve 10 mA · cm-2 and delivering a current density of 363 mA · cm-2 at 1.7 V vs. RHE. X-ray photoelectron spectroscopy indicated that the enhanced activity of Fe24Ni76 originated from increased oxidation of metallic Ni and a higher density of catalytically active oxide species. These results demonstrate that sputtered NiFe thin films, particularly at optimized compositions, are promising scalable and low-cost OER electrodes for next-generation water electrolysis systems.