Acta Phys. -Chim. Sin. ›› 2023, Vol. 39 ›› Issue (11): 2212011.doi: 10.3866/PKU.WHXB202212011

• ARTICLE • Previous Articles     Next Articles

Construction of Z-Scheme MnO2/BiOBr Heterojunction for Photocatalytic Ciprofloxacin Removal and CO2 Reduction

Jintao Dong1, Sainan Ji2, Yi Zhang1, Mengxia Ji1, Bin Wang1, Yingjie Li1, Zhigang Chen2, Jiexiang Xia1,*(), Huaming Li1   

  1. 1 School of Chemistry and Chemical Engineering, Institute for Energy Research, Jiangsu University, Zhenjiang 212013, Jiangsu Province, China
    2 School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu Province, China
  • Received:2022-12-06 Accepted:2023-02-17 Published:2023-02-28
  • Contact: Jiexiang Xia E-mail:xjx@ujs.edu.cn
  • Supported by:
    the Postgraduate Research & Practice Innovation Program of Jiangsu Province(KYCX22_3692);the National Natural Science Foundation of China(21878134);the National Natural Science Foundation of China(22108106);the National Natural Science Foundation of China(22108108);the China Postdoctoral Science Foundation(2020M680065);the Hong Kong Scholar Program(XJ2021021)

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Abstract:

Rapid increase in energy shortage and ecological environmental pollution has become a major issue that has been continuously drawing global attention, because it severely affects human health and limits sustainable social development. Various technologies have been developed and used to rationalize the utilization of new energy sources and pollution control. Among these technologies, photocatalysis has become a research priority in the field of environmental governance and energy development. Advantages such as low energy consumption, no secondary pollution, simple operation methods, and mild reaction conditions make photocatalysis an attractive choice. Notably, although photocatalysis is a promising approach for enhancing antibiotic removal and CO2 reduction efficiency, the industrialization and large-scale application of photocatalysts is limited because of issues such as low photo-absorption efficiency, redox capacity, and photogenerated electron separation or migration efficiency. The progress of current research on the regulation of composition/structure and performance of photocatalysts has promoted the exploration of efficient and practical modification strategies to construct photocatalyst composites with improved performance by facilitating light absorption/utilization and enhancing photocatalytic surface/interface reaction performance. Among the many common modification strategies, the construction of a Z-scheme heterojunction can enhance the light absorption ability and significantly reduce the recombination rate of photogenerated electron-hole pairs. Additionally, this strategy maintains the strong reduction/oxidation ability of photogenerated electrons/holes to facilitate the oxidation of environmental pollutants and conversion to clean energy. In this study, Z-scheme MnO2/BiOBr (MO/BiOBr) composites were effectively constructed using a mechanically assisted ball-milling process. In situ X-ray photoelectron spectroscopy under dark and light conditions confirmed that photoexcited electrons in MnO2 can migrate directionally to BiOBr through Mn3+/Mn4+ redox couple to create a Z-scheme transfer path. A similar conclusion can also be deduced from the results of electron spin-resonance spectroscopy and band structure analysis. The formation of a Z-scheme heterojunction between MnO2 and BiOBr, attributed to the Mn3+/Mn4+ redox couple from MnO2 and staggered energy band, enabled the space separation of oxidation and reduction centers. Furthermore, compared with BiOBr, MO/BiOBr composites exhibited enhanced light absorption and a markedly reduced photoinduced electron-hole pair recombination rate, as confirmed by ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. Thus, the MO/BiOBr composites exhibited exceptional photocatalytic performance toward ciprofloxacin (CIP) oxidation and CO evolution. The CIP removal efficiency of the MO/BiOBr composites reached 77.3% in just 60 min, which is 1.28 times higher than that of BiOBr (60.2%). Simultaneously, the photocatalytic CO2-to-CO performance of the MO/BiOBr composites (20.02 µmol·g−1·h−1) was found to be 2.20-fold higher than that of BiOBr (9.08 µmol·g−1·h−1). Photocurrent measurement and electrochemical impedance spectroscopy indicated that the MnO2/BiOBr Z-scheme heterojunction has higher interfacial electron transfer efficiency than pure MnO2 and BiOBr. Additionally, liquid chromatograph mass spectrometry and in situ Fourier transform infrared spectroscopy is conducted to study the generation of intermediates during the photocatalytic CIP removal and CO2 reduction process. The toxicity of CIP and corresponding intermediates after the photocatalytic degradation of the MO/BiOBr composites was evaluated using toxicity estimation software (T.E.S.T.) to analyze the actual physiological toxicity, based on indexes such as Daphnia Magna lethal concentration 50% (LC50, 48 h), Fathead Minnow lethal dose 50% (LD50, 96 h), mutagenicity, and bioaccumulation factor. Thus, this study proposed a novel and simplified approach for constructing a Z-scheme heterojunction to facilitate solar-derived antibiotic removal and fuel synthesis.

Key words: Z-scheme heterojunction, BiOBr, Ciprofloxacin removal, CO2 reduction, Photocatalysis