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

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 P x -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 Co 3+ 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 P x -CoO NSs show superior OER activity compared with pure CoO and IrO 2 as benchmark. Furthermore, P 1 -CoO NSs demonstrate intrinsically high mass activity of 6.8 A g Co −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.