Interface engineering of defected earth-abundant transition metal oxo-phospho-selenide-derived electrocatalyst for high-performance AEM water electrolysis

This study introduces a cost-effective, high-performance electrocatalyst based on non-noble metals for anion exchange membrane water electrolysis (AEMWE), crucial for sustainable hydrogen production. We describe a NiMn-oxo-phospho-selenide (NiMn-OPSe) catalyst, synthesized via a simple two-step method involving hydrothermal synthesis and controlled phospho-selenization. This approach combines morphology control, interface engineering, coordination tuning, and defect engineering, resulting in a needle-like structure that optimizes charge-transfer pathways and tunes the electronic structure, thereby enhancing catalytic performance. The NiMn-OPSe catalyst demonstrates outstanding HER and OER activities with ultralow overpotentials of 69 mV and 269 mV, respectively, at 10 mA cm⁻² in 1.0 M KOH medium, thus resulting in a low cell voltage of 1.57 V for overall water splitting, surpassing many non-noble metal catalysts and approaching noble-metal-level performance. Moreover, efficient performance of the fabricated AEMWE device is confirmed by requiring only 1.94 V to reach 500 mA cm⁻², along with excellent stability over 500 h. Operando Raman spectroscopy reveals enhanced water dissociation capability, while water contact angle analysis confirms superior wettability. Density functional theory (DFT) calculations show that the NiSe/Ni₈P₃/MnCO₃ heterointerface optimizes hydrogen adsorption with near-zero ΔG_H⁎ and enhances electronic properties through d-band center modulation, confirming the intrinsic catalytic advantages of the developed NiMn-OPSe material.