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Abstract

We present a systematic investigation of the microscopic mechanism of interface interaction, charge transfer and separation, as well as their influence on the photocatalytic activity of heterojunctions by a combination of theoretical calculations and experimental techniques for the g-C³N⁴-ZnWO⁴ composite. HRTEM results and DFT calculations mutually validate each other to indicate the reasonable existence of g-C³N⁴ (001)-ZnWO⁴ (010) and g-C³N⁴ (001)-ZnWO⁴ (011) interfaces. The g-C³N⁴-ZnWO⁴ heterojunctions show higher photocatalytic activity for degradation of MB than pure g-C³N⁴ and ZnWO⁴ under visible-light irradiation. Moreover, the heterojunctions significantly enhance the oxidation of phenol in contrast to pure g-C³N⁴, the phenol oxidation capacity of which is weak, clearly demonstrating a synergistic effect between g-C³N⁴ and ZnWO⁴. Interestingly, based on the theoretical calculations, we find that electrons in the upper valence band can be directly excited from g-C³N⁴ to the conduction band, that is, the W 5d orbital of ZnWO⁴, under visible-light irradiation, which should yield well-separated electron-hole pairs, with high photocatalytic performance in g-C³N⁴-ZnWO⁴ heterojunctions as shown by our experiment. The microcosmic mechanisms of interface interaction and charge transfer in this system can be helpful for fabricating other effective heterostructured photocatalysts.