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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.

Oxygen vacancies (Ovac) can improve electrocatalytic activities in the oxygen evolution reaction (OER) process but remain a great challenge. Herein, we report a facile two-step approach to synthesizing La-doped CoOx nanosheets (NSs) with abundant oxygen vacancies by a La-triggered effect. Profiting from enriched Ovac and fast charge transfer, La-doped CoOx NSs deliver a remarkably high OER activity with a low overpotential of 353 mV at 10.0 mA cm−2 and a Tafel slope of 78.2 mV dec−1, surpassing those of initial CoOx, IrO2, and most reported non-noble metal based electrocatalysts. In addition, they also exhibit superior durability with only slight degradation after continuous operation of 35 h in a 0.1 M KOH solution. Undoubtedly, the results inspire the use of La into the oxygen vacancies to explore highly active catalysts for various applications.