Mesoporous Nanosheet Networked Hybrids of Cobalt Oxide and Cobalt Phosphate for Efficient Electrochemical and Photoelectrochemical Oxygen Evolution

A novel mesoporous nanosheet networked hybrid comprising Co3O4 and Co3(PO4)2 is successfully synthesized using a facile and scalable method through calcinating the carbon, cobalt hydroxy carbonate, and cobalt phosphate composite precursor. Electron transfer from Co3O4 to Co3(PO4)2, together with the special networked structure and the porous nature of the nanosheets enable the Co3(PO4)2‐Co3O4 hybrid to have a high oxygen evolution reaction (OER) activity and outstanding stability in alkaline electrolyte, e.g., an overpotential of 270 mV at current density of 10 mA cm−2, and a Tafel slope of 39 mV dec−1, which are superior to most non‐noble metal‐based OER electrocatalysts reported thus far and as well the commercial RuO2 electrocatalyst. Furthermore, Co3(PO4)2‐Co3O4 hybrid is demonstrated to be used as an efficient cocatalyst to enhance the photoelectrochemical OER performance of BiVO4 photoanode. A significantly increased photocurrent density of 3.0 mA cm−2 at 1.23 V (vs reversible hydrogen electrode, RHE), and a potential reduction of 530 mV with respect to that of bare BiVO4 at the photocurrent density of 0.5 mA cm−2 are achieved. The electron transfer‐induced enhancement of OER by a hybrid structure may pave the new routes for the design and synthesis of low‐cost catalysts for electrochemical and photoelectrochemical oxygen evolution. A novel networked mesoporous nanosheet hybrid composed of Co3O4 and Co3(PO4)2 is synthesized through calcinating the carbon, cobalt hydroxy carbonate, and cobalt phosphate composite precursor. Beneficial from the collective effects of special morphological design and the synergistic enhancement effect between ingredients, the Co3(PO4)2‐Co3O4 nanocomposite exhibits very high activities and excellent stabilities for the electrochemical and photoelectrochemical oxygen evolution reaction.