Anti-defect Engineering of Crystalline g-C3N4 Nanostructures for Efficient Photocatalytic In Situ H2O2 Production

How to realize on-site small-scale production and sustainable consumption of H2O2 is the focus of attention of this study. Photocatalysis technology can just meet this demand, and g-C3N4 is one of the most popular catalysts employed. However, the numerous defects in the g-C3N4 nanostructure seriously inhibit its catalytic activity, which act as recombination centers of photogenerated carriers. Herein, we propose an anti-defect engineering strategy to tailor a highly crystalline g-C3N4 nanostructure for efficient photocatalytic in situ H2O2 production, which can be further cascaded to wastewater remediation. High-resolution transmission electron microscopy and electron spin-resonance spectroscopy results demonstrate that highly crystalline g-C3N4 is successfully fabricated with extremely low defect concentrations. Transient surface photovoltage data shows that highly crystalline g-C3N4 exhibits rapid charge separation and transfer with slow decay. Therefore, the photocatalytic activity of g-C3N4 can be significantly promoted by eliminating its defects to construct a highly crystalline structure. Especially, the crystalline g-C3N4 prepared by thiourea (CNT) exhibits the maximum H2O2 production of 2.48 mmol g–1 h–1 with an apparent quantum efficiency of 22% (λ = 400 nm), along with an excellent cascade tetracycline removal effect. This work provides an anti-defect engineering strategy to regulate the crystal structure of the catalyst for its enhanced photocatalytic activity.