Energy band engineering of graphitic carbon nitride for photocatalytic hydrogen peroxide production

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AbstractHydrogen peroxide (H2O2) is one of the 100 most important chemicals in the world with high energy density and environmental friendliness. Compared with anthraquinone oxidation, direct synthesis of H2O2 with hydrogen (H2) and oxygen (O2), and electrochemical methods, photocatalysis has the characteristics of low energy consumption, easy operation and less pollution, and broad application prospects in H2O2 generation. Various photocatalysts, such as titanium dioxide (TiO2), graphitic carbon nitride (g‐C3N4), metal‐organic materials, and nonmetallic materials, have been studied for H2O2 production. Among them, g‐C3N4 materials, which are simple to synthesize and functionalize, have attracted wide attention. The electronic band structure of g‐C3N4 shows a bandgap of 2.77 eV, a valence band maximum of 1.44 V, and a conduction band minimum of −1.33 V, which theoretically meets the requirements for hydrogen peroxide production. In comparison to semiconductor materials like TiO2 (3.2 eV), this material has a smaller bandgap, which results in a more efficient response to visible light. However, the photocatalytic activity of g‐C3N4 and the yield of H2O2 were severely inhibited by the electron‐hole pair with high recombination rate, low utilization rate of visible light, and poor selectivity of products. Although previous reviews also presented various strategies to improve photocatalytic H2O2 production, they did not systematically elaborate the inherent relationship between the control strategies and their energy band structure. From this point of view, this article focuses on energy band engineering and reviews the latest research progress of g‐C3N4 photocatalytic H2O2 production. On this basis, a strategy to improve the H2O2 production by g‐C3N4 photocatalysis is proposed through morphology control, crystallinity and defect, and doping, combined with other materials and other strategies. Finally, the challenges and prospects of industrialization of g‐C3N4 photocatalytic H2O2 production are discussed and envisioned.