Creation of direct Z-scheme Al/Ga co-doping biphasic ZnO/g-C3N4 heterojunction for the sunlight-driven photocatalytic degradations of methylene blue
Al and Ga were co-doped into ZnO lattice (AGZ) by the sol–gel method. Herein, graphite carbon nitride (g-C 3 N 4 ) was synthesized by using the thermal decomposition method, which was used to integrate with the obtained AGZ to create direct Z-scheme Al/Ga co-doping biphasic ZnO/g-C 3 N 4 heterojunction by the simple single-phase dispersion method. The synthesized catalysts of composition, optical properties, topography structure and chemical state of element of the prepared AGZ/g-C 3 N 4 composites were analyzed by XRD, FT-IR, UV, PL, TEM and XPS respectively. The results have shown that the combination of AGZ and g-C 3 N 4 to form a direct Z-type heterojunction can effectively reduce the band gap of AGZ, thereby shifting the absorption edge to the visible light region. The PL spectroscopy study of the synthesized sample found that, compared with bare g-C 3 N 4 or AGZ catalyst, AGZ/g-C 3 N 4 significantly reduced the recombination of photogenerated electrons and holes, thereby ensuring that more reactive groups participate in the dye degradation process. The degradation experiment of methylene blue(MB) dye verifies that the AGZ/CN sample has excellent photocatalytic performance. Al/Ga co-doped ZnO/g-C 3 N 4 catalyst showed the maximum photocatalytic MB degradation of 95.4% after 150 min in visible light illumination, while the degradation efficiency of ZnO and g-C 3 N 4 are only 30.5% and 50.1%, respectively. It have observed that ·O 2 − , ·OH and h + radicals were the main active species that affect the photocatalytic degradation of dyes by radical trapping experiment. In addition, the heterojunction formed by AGZ and g-C 3 N 4 inhibited the photocorrosion of ZnO, which was confirmed by these five consecutive dye degradation tests. At the same time, in order to determine the optimal compounding ratio, four groups of AGZ/CN with different ratios were prepared. It was found that AGZ/CN15 has the highest catalytic efficiency, and the degradation of MB reached 94% within 2.5 h. This work will open up a new path for the development of more effective photocatalysts for organic matter treatment. Graphical abstract
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