Electronic Modulation and Surface Reconstruction of NiS2 for Enhanced Alkaline Oxygen Evolution Reaction Activity and Durability.

Practical anion exchange membrane water electrolysis (AEMWE) requires non-noble-metal oxygen evolution reaction (OER) anodes that deliver high activity while maintaining structural integrity under alkaline operation. Here, Fe-substituted Ni disulfide (Ni1-xFexS2, NFS-x) is designed as a conductive Fe-modulated sulfide framework and combined with alkaline pretreatment (AT) to pre-form a NiFe (oxy)hydroxide-rich surface before electrolysis. DFT calculations show that Fe substitution narrows the NiS2 band gap by ∼0.44 eV and lowers the free-energy barrier for the rate-determining *O → *OOH step by 0.59 eV, while spectroscopic analysis indicates an increased average Ni oxidation state. The optimized NFS-15 achieves an overpotential of 286 mV at 10 mA cm-2. AT produces a largely amorphous/poorly crystalline NiFe (oxy)hydroxide-rich outer layer on the retained sulfide core, confining subsequent reconstruction, suppressing catalyst detachment, and enabling superhydrophilicity-assisted bubble release. In an AEMWE single cell, the NFS-15-AT/NF anode reaches 1 A cm-2 at 1.65 V, outperforms commercial IrO2 under identical conditions, and maintains stable operation for >200 h. This work demonstrates that integrating Fe-induced electronic modulation of the sulfide framework with surface-confined pre-reconstruction provides an effective route to durable sulfide-derived anodes for practical AEMWE.