Fe-doped and sulfur-enriched Ni₃S₂ nanowires with enhanced reaction kinetics for boosting water oxidation

Exploring cost-effective and highly-active oxygen evolution reaction (OER) electrocatalysts is a pressing task to propel water electrolysis for green hydrogen production. Herein, we constructed a class of Fe-doped and S-enriched Ni₃S₂ nanowires electrocatalysts for optimizing the target intermediates adsorption to decrease the OER overpotentials at various current densities. The optimal Ni₃S₂-1.4%Fe electrocatalyst possesses the most active sites and exhibits an ultralow overpotential of 190 mV at 10 mA cm⁻² with an excellent stability of > 60 h, exceeding the majority of recently-reported Ni₃S₂-based electrocatalysts. The trivalence Fe-doping not only reduces the electron density of the Ni center, but also enables the sulfur enrichment on the Ni₃S₂ surface, which greatly improves the intrinsic activity and the number of target intermediates (∗OOH). A novel methanol-assisted electrochemical evaluation further reveals that the Ni₃S₂-1.4%Fe electrocatalyst demonstrates a weaker binding ability to ∗OH with the rapid generation of ∗OOH species, and thus gives a lower apparent activation energy compared with the surface sulfur reduced ones. This work provides a new perspective for regulating the adsorption of intermediates through doping strategy.