Carbon Vacancy-Induced Exciton Dissociation in Graphitic Carbon Nitride for Photocatalytic H2O2 Production Coupled with Benzyl Alcohol Oxidation

Abstract Photocatalytic efficiency for H2O2 production on graphitic carbon nitride (g-C3N4) is limited by the relatively low separation efficiency of photocarriers and the sluggish kinetics of the consumption of photogenerated holes. Herein, g-C3N4 with carbon vacancies (Cv-CN) is prepared for photocatalytic H2O2 production coupled with benzyl alcohol (BzOH) oxidation. The carbon vacancies reduce the exciton binding energy, thus increasing the separation and transfer of photocarriers. The coupled BzOH oxidation accelerates the kinetics of consumption of photogenerated holes. The H2O2 production rate on Cv-CN is enhanced to approximately five times that of g-C3N4 without carbon vacancies. Meanwhile, BzOH is oxidized to benzaldehyde and benzoic acid, with selectivities of 60.1% and 32.0%, respectively. It is found that H2O2 is produced by the reduction of O2 by the photogenerated electrons through •O2– and •OOH intermediates. BzOH is oxidized to benzaldehyde mainly by photogenerated holes, but the further oxidation of benzaldehyde to benzoic acid is contributed by photogenerated holes and reactive oxygen species. Our findings not only demonstrate the photocatalytic H2O2 production coupled with value-added chemical synthesis but also deepen the understanding of the function of carbon vacancies in g-C3N4 for photocatalysis.