Carbon-Supported Oxygen Vacancy-Rich Co₃O₄ for Robust Photocatalytic H₂O₂ Production via Coupled Water Oxidation and Oxygen Reduction Reaction

Photocatalytic H 2 O 2 production is a promising strategy to alleviate energy crisis, since H 2 O 2 is an important liquidus chemical and fuel. However, the following problems severely restrict the development of this technique: (1) low selectivity; (2) low stability (normally less than five short-time cycles); (3) fast charge recombination; (4) assistance of hole scavengers; and (5) demand of O 2 saturation. Herein, carbon-supported oxygen vacancy-rich Co 3 O 4 nanoplate (C-ovCo) is reported as an efficient photocatalyst for scavenger-free H 2 O 2 production by coupled 2e – water oxidation (WOR) and 2e – oxygen reduction reaction (ORR) with low energy barrier of 1.1 eV. In this system, the oxygen vacancies can reduce the band gap, enhance the donor density, improve the charge separation and migration, and work as WOR sites, while the carbon support accepts electrons and works as ORR sites. The photocatalysts exhibit an optimal H 2 O 2 production rate of 3.78 mmol h –1 g –1 under visible light (λ ≥ 420 nm), an apparent quantum efficiency of 16.7% at 420 nm, and a solar-to-chemical efficiency of 0.4%. Moreover, the stability of over 720 h (30 long-time cycles) is also superior to the state-of-the-art photocatalytic systems.