Cationic Oxidative Leaching Engineering Modulated In Situ Self-Reconstruction of Nickel Sulfide for Superior Water Oxidation

Tuning the electroactive surface species of electrocatalysts remains a significant challenge for achieving highly efficient oxygen evolution reactions. Herein, we propose an innovative in situ leaching strategy, modulated by cationic oxidation, to achieve active self-reconstruction of these catalysts. Vanadium is introduced as a cation into Ni₃S₂ and oxidized under low oxidative potential, leading to subsequent leaching into the electrolyte and triggering self-reconstruction. The structural evolution from V-Ni₃S₂ to Ni(OH)₂ and subsequently to NiOOH is identified by operando Raman as a three-step transition. In contrast, V-free Ni₃S₂ is unable to bypass the thermodynamically predicted nickel oxysulfide products to transform into active NiOOH. As a result, the self-restructured V-Ni₃S₂ only needs an ultralow overpotential of 155 mV at 10 mA cm^-2, outperforming V-free Ni₃S₂ and many other advanced catalysts. This work provides new guidelines for manipulating in situ leaching to modulate the self-reconstruction of catalysts.