NGO/ZnO2/ZnO Heterojunctions with Self-Accelerating Photocatalysis for Efficient Degradation of Organic Dyes

Photocatalytic degradation of dyes using semiconductor materials has received widely attention. We employed ZnO2 as a zinc source and synthesized NGO/ZnO2/ZnO heterojunctions with self-accelerated photocatalytic function by hydrothermal technique and investigated their photocatalytic degradation performance of RhB and MO under simulated sunlight irradiation. NGO greatly improved the adsorption performance of NGO/ZnO2/ZnO on dyes, among which, the adsorption of MO dyes was 11 times higher than that of ZnO2/ZnO. While enhancing the sunlight absorption range and adsorption performance, the NGO could also rapidly transfer electrons and effectively inhibit the complexation of electron-hole pairs, further improving the photocatalytic performance. By optimizing the doping ratio of NGO, NGO/ZnO2/ZnO with the highest photocatalytic degradation activity was obtained, which was 4.4 times higher than that of ZnO2/ZnO. In addition, the acid-base resistance and cycling experiments showed that the NGO/ZnO2/ZnO-3 photocatalyst had good stability. The EPR experiments showed that ·O2− and ·OH radicals were extremely important active substances in the whole photodegradation process. Finally, the synergistic enhancement mechanism of the photocatalytic performance of ZnO by NGO and ZnO2 was revealed. This work provides a good strategy for designing ZnO composite photocatalysts to efficiently degrade organic dyes.