Defects modified in the exfoliation of g-C3N4 nanosheets via a self-assembly process for improved hydrogen evolution performance

Abstract

In this work, self-assembly g-C3N4 samples were prepared without templates by a facile method involving thermal oxidation etching of bulk g-C3N4 and subsequent reflux in the different organic solvent at a low temperature. The internal hydrogen bond, cyano and amino defects of g-C3N4 nanosheets can be partly repaired via refluxing in the different polarity of the organic solvent, which is attributed to the effect of hydrogen bond polarity, hydroxyl and carbon chain structure of organic solvent. Especially, refluxing in the solvent of isopropanol, g-C3N4 nanosheets have transformed into quasi-sphere structure via a self-assembly process utilizing the effect of Oswald, which evidently reduced defect density within a molecular of g-C3N4, because of strong interaction between the generation of C–O bond of g-C3N4 nanosheets during refluxing in the isopropanol solvent and molecular group of isopropanol (hydroxyl group and the carbon chain structure). The self-assembly quasi-sphere g-C3N4 samples exhibit much faster photocatalytic hydrogen evolution rate than other g-C3N4 samples under visible light irradiation and the hydrogen evolution rate is 30.67 μmol h−1, which is about 10 times higher than that of bulk g-C3N4. The enhanced hydrogen evolution performance for quasi-sphere g-C3N4 samples is ascribed to large surface areas and accelerated separation of charges.