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

Abstract A novel mesoporous nanosheet networked hybrid comprising Co 3 O 4 and Co 3 (PO 4 ) 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 Co 3 O 4 to Co 3 (PO 4 ) 2 , together with the special networked structure and the porous nature of the nanosheets enable the Co 3 (PO 4 ) 2 ‐Co 3 O 4 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 RuO 2 electrocatalyst. Furthermore, Co 3 (PO 4 ) 2 ‐Co 3 O 4 hybrid is demonstrated to be used as an efficient cocatalyst to enhance the photoelectrochemical OER performance of BiVO 4 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 BiVO 4 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.