LAUSR

The density functional theory calculation results reveal that the adjacent defect concentration and electronic spin state can effectively activate the CoIII sites in the atomically thin nanosheets, facilitating the thermodynamic transformation of *O to *OOH, thus offering ultrahigh charge transfer properties and efficiently stabilizing the phase. This undoubtedly evidences that, for metal sulfides, the atom-scale cation/anion vacancy pair and surface electronic spin state can play a great role in enhancing the oxygen evolution reaction. Inspired by the theoretical prediction, interconnected selenium (Se) wired ultrathin Co3 S4 (Sex -Co3 S4 ) nanosheets with Co/S (Se) dual-vacancies (Se1.0 -Co3 S4 -VS/Se -VCo ) pairs are constructed by a simple approach. As an efficient sulfur host material, in an ultralow-concentration KOH solution (0.1 m), Se1.0 -Co3 S4 -VS/Se -VCo presents outstanding durability up to 165 h and a low overpotential of 289.5 mV at 10 mA cm-2 , which outperform the commercial Co3 S4 nanosheets (NSs) and RuO2 . Moreover, the turnover frequency of Se1.0 -Co3 S4 -VS/Se -VCo is 0.00965 s-1 at an overpotential of 0.39 V, which is 5.7 times that of Co3 S4 NSs, and 5.8 times that of commercial RuO2 . The finding offers a rational design strategy to create the multi-defect structure in catalysts toward high-efficiency water electrolysis.