| WU Min-ke,REN Lu,REN Rui-xiang,LI Jia-hao,ZHAO Chao-fan,YU Yang.Research Progresses on Photocatalytic Properties of Z-scheme Heterojunction Structures Based on ZnO[J],52(11):200-215 |
| Research Progresses on Photocatalytic Properties of Z-scheme Heterojunction Structures Based on ZnO |
| Received:August 15, 2022 Revised:March 01, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.11.015 |
| KeyWord:ZnO Z-scheme heterojunction photocatalysis semiconductor organic pollutants |
| Author | Institution |
| WU Min-ke |
School of Civil Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou, , China |
| REN Lu |
School of Civil Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou, , China |
| REN Rui-xiang |
School of Civil Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou, , China |
| LI Jia-hao |
School of Civil Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou, , China |
| ZHAO Chao-fan |
School of Civil Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou, , China |
| YU Yang |
School of Civil Engineering, Suzhou University of Science and Technology, Jiangsu Suzhou, , China |
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| Abstract: |
| As a common photocatalyst, Zinc oxide (ZnO) has some defects, such as poor utilization of light energy, low efficiency and easy deactivation, which limit its wide applications. It is one of the hotspots to solve the above problems to construct ZnO-based heterojunction structures by selecting semiconductor materials that can match the ZnO-band gap structure. Recently, forming Z-scheme heterojunction of ZnO is a new approach to improve its photocatalytic performance because its electron transfer process forms the shape of the English letter Z . This paper systematically introduced the research progress of nano ZnO photocatalytic efficiency improvement from three aspects:Z-scheme heterojunction structure, binary Z-scheme heterojunction structure, and ternary Z-scheme heterojunction structure. Firstly, heterojunction structures and Z-scheme heterojunction structure were explained in details. Heterojunction structures referred to the contact interfaces between two semiconductor materials with different band structures. Among them, Type-Ⅱ type heterojunction structures were arranged in a staggered manner of the two bands, which was the most studied traditional heterojunction structure. Different from Type-Ⅱ traditional heterojunction, the specific carrier migration process of Z-scheme heterojunction structure was as follows:the electrons in the conduction band of the semiconductor Ⅱ recombined with the holes in the valence band of the semiconductor Ⅰ. Meanwhile, the residual electrons mainly existed in the conduction band of semiconductorⅠ, and the holes mainly existed in the valence band of semiconductor Ⅱ. Thus, Z-scheme heterojunction structure had a higher separation efficiency of photogenerated carriers and maintained a high redox capacity. Secondly, ZnO-based binary Z-scheme heterojunction structures were discussed and the mechanisms of the improved of catalytic performance were summarized. Those binary Z-scheme heterojunctions were formed by ZnO with semiconductor oxides (e.g. WO3/ZnO, TiO2/ZnO, CeO2/ZnO, Cu2O/ZnO), semiconductor sulfides (e.g. ZnS/ZnO, CdS/ZnO), and other semiconductor materials (e.g. g-C3N4/ZnO, Ag3PO4/ZnO). The photogenerated electrons retained in the conduction band of ZnO or matched semiconductor maintain high reduction capacity, and the photogenerated holes retained in the valence band of matched semiconductor or ZnO maintain high oxidation capacity. Eventually, the composite catalyst showed better photocatalytic activity. The binary Z-scheme heterojunction constructed with the visible-light semiconductor catalyst could also promote the light response range of ZnO-based photocatalyst from ultraviolet light to visible light, which improved the utilization of light energy, and solved the limitation of ZnO excited only by ultraviolet light. Thirdly, the photocatalytic mechanism of ternary heterojunction and the advantages of ternary Z-scheme heterojunction in photocatalytic performance were reviewed. The ZnO-based ternary Z-scheme heterojunction structure was more complex than the binary heterojunction in terms of composition and charge migration. The most common type of ternary Z-scheme heterojunction was the inclusion of noble metal as an intermediate electron medium between two semiconductor materials (e.g. ZnO-Ag-BiVO4, ZnO-Au-ZnAl2O4). The ternary Z-scheme heterojunction structure of noble metal-ZnO system also could be built through the ZnO-based binary Z-scheme heterojunctions further modified by noble metals (e.g. Au-g-C3N4-ZnO). Other constructions of ternary Z-type heterojunctions were composed of three kinds of semiconductor materials, resulting in a double Z-scheme charge transport (e.g. ZnO/ZnWO4/g-C3N4, Bi2MoO6/ZnSnO3/ZnO). Finally, the research prospect of Z-scheme heterojunctions was summarized. Compared with pure ZnO photocatalyst, ZnO-based Z-scheme heterojunction structure had more potential in the catalysts design, and had more advantages in degradation of organic pollutants, hydrogen production and other photocatalysis. That provides a reference for the design, preparation and performance improvement of other semiconductor materials. |
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