Phosphorus-induced reconstruction of Sub‐2 nm ultrafine spinel type CoO nanosheets for efficient water oxidation

•A covalent doping approach was employed to prepare ultrathin CoO nanosheets.•P1-CoO NSs rich with P–O bonds gave excellent alkaline OER activity and durability.•P1-CoO NS exhibits intrinsically high mass activity and large turnover frequency.•The ordered Ovac and P-activation synergistically optimized the electronic states of CoO. A phosphorus-triggered synergy of ~1.0 nm ultrathin CoO nanosheets and O vacancy migration leads to high mass activity and turnover frequency for Co-based oxides toward the oxygen evolution reaction. [Display omitted] The surface configuration of low‐cost spinel oxides for oxygen evolution reaction (OER) can significantly affect the electrochemical behavior by generating a thin oxyhydroxide layer and other structures on the surface. Herein, we design and construct phosphorus (P)-activated ~1.0 nm ultrathin CoO nanosheets (devoted as Px-CoO NSs) with enriched P-O bonds and high valence state Co active sites, which is beneficial to the OER process due to the balance with Co3+ and oxygen vacancies on the reconstructed surface/interface. In addition, such an ultrathin nanosheet structure is also benefit to expose more active sites and improve the intrinsic electronic conductivity. As a result, the surface reconstructed Px-CoO NSs show superior OER activity compared with pure CoO and IrO2 as benchmark. Furthermore, P1-CoO NSs demonstrate intrinsically high mass activity of 6.8 A gCo−1 at an overpotential of 270 mV, large turnover frequency of 0.0024 s−1 at an overpotential of 300 mV, and strong cycling stability in 0.1 M KOH solutions. Structural analysis further reveals that, as compared with CoO, the P-substitution not only induces the surface reconstruction into active Co oxyhydroxides under OER conditions, but also enhances the reaction kinetics. Undoubtedly, this work enriches the ways to prepare high-performance transition-metal-oxide-based catalyst for practical applications.