Control of carbon vacancies in g-C3N4 photocatalyst via wood pyrolysis induced etching strategy

Abstract

Post-thermal treatment is a widely employed technique for the fabrication of graphitic carbon nitride (g-C3N4) with thin-layered, porous and defect-rich structures for photocatalytic hydrogen evolution. Here, the synthesis of catalysts is assisted with wood pyrolysis, which triggers an etching on g-C3N4 by released trace carbon oxides gases. Specifically, a nickel foam is used as the substrate to hold a piece of pine wood on top of bulk g-C3N4, thereby preventing interfacial structural damage and introduction of impurities in a conventionally used solid state mixing process. Such a multicomponent atmosphere results g-C3N4 with tunable carbon vacancies (TCCNx) and small particle sizes, and therefore a large specific surface area is obtained. The as-prepared TCCNx exhibits an improved photocatalytic hydrogen evolution rate of 3703 μmol·g−1·h−1, outperforming the bulk g-C3N4 by ∼20 folds under visible light (λ > 420). The reason for enhanced photocatalytic performance is ascribed to a favorable optical property, rapid charge carrier separation, and efficient charge transfer processes. This unique top-down etching strategy provides valuable insights for designing efficient polymer photocatalysts with controllable properties.