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Developing efficient and durable oxygen evolution electrocatalyst is of paramount importance for the large-scale supply of renewable energy sources. Herein, we report a design of significant surface hydrophilicity based on the cobalt oxyhydroxide (CoOOH) nanosheets to greatly improve the surface hydroxyl species adsorption and reaction kinetics at the Helmholtz double layer for high-efficiency water oxidation activity. The as-designed CoOOH-Graphene nanosheets achieve a small surface water contact angle of ~23° and a large double-layer capacitance (Cdl) of 8.44 mF/cm2, thus could evidently strengthen surface species adsorption and trigger electrochemical oxygen evolution reaction (OER) under a quite low onset potential of 200 mV with an excellent Tafel slope of 32 mV/dec. X-ray absorption spectroscopy and first-principles calculations demonstrate that the strong interface electron coupling between CoOOH and graphene extracts partial electrons from the active sties and increases the electron state density around the Fermi level, and effectively promotes the surface intermediates formation for efficient OER.

Highly efficient oxygen evolution driven by abundant sunlight is a key to realize overall water splitting for large-scale conversion of renewable energy. Here, we report a strategy for the interfacial atomic and electronic coupling of layered CoOOH and BiVO4to deactivate the surface trapping states and suppress the charge-carrier recombination for high photoelectrochemical (PEC) water oxidation activity. The successful synthesis of a 3D ultrathin-CoOOH-overlayer-coated coral-like BiVO4photoanode effectively tailors the migration route of photocarriers on the semiconductor/liquid interface to realize a great increase of ∼200% in the photovoltage relative to bare BiVO4, consequently decreasing the corresponding onset potential of PEC water splitting from 0.60 to 0.20 VRHE. As a result, the unique CoOOH/BiVO4photoanode could efficiently perform PEC water oxidation in a neutral aqueous solution (pH = 7) with a high photocurrent density of 4.0 mA/cm2at 1.23 VRHEand a prominent quantum efficiency of 65% at 450 nm. Electronic structural characterizations and theoretical calculations reveal that the combination of layered CoOOH and BiVO4forming interfacial oxo-bridge bonding could greatly eliminate surface trapping states and promote the direct transfer of photogenerated holes from the valence band to the surface water redox potential for water oxidation.