SHI Shunchao, ZHANG Hailun, WANG Jiansheng, ZENG Xiongfeng

(Hebei Province Laboratory of Inorganic Nonmetallic Materials, College of Material Science and Engineering, North China University of Science and Technology, Tangshan 063210, Hebei, China)

Extended Abstract:[Significance] With the acceleration of industrialization, environmental problems such as water pollution have become increasingly severe. Photocatalytic technology represented by TiO₂ provides a new solution to environmental pollution problems and lays the foundation for applications in fields such as photocatalysis, solar energy conversion and environmental pollution control. However, the low quantum efficiency of TiO₂, large band gap and insufficient utilization of visible light seriously restrict its practical applications. Localized surface plasmon resonance (LSPR) based on noble metals (Au, Ag, Pt) has been proven to be an effective strategy to enhance photocatalytic performance. However, the high cost of noble metals limits their large-scale applications. This paper is aimed to summarize the mechanism and key issues of LSPR-enhanced photocatalytic activity, by focusing on the latest research progress in achieving plasmon-enhanced photocatalytic performance by modifying TiO₂ with non-noble metals such as transition metals, rare earth metals and main group metals, thus providing theoretical basis and technical reference for the development of efficient and low-cost photocatalysts.[Progress] This article is aimed to elaborate the specific application scenarios of improvement in photocatalytic performance of TiO₂ by utilizing the Localized Surface Plasmon Resonance (LSPR) effect. How the materials, sizes, shapes of metal nanoparticles, and the refractive index of the surrounding medium affect the intensity of the LSPR effect will be discussed. Meanwhile, the specific applications of using non-noble metals to modify TiO₂ to form plasmons and enhance the photocatalytic performance through the LSPR effect will be overviewed. Subsequently, they will be compared with the traditional modification approaches with noble metals. It is particularly emphasized that non-noble metals possess characteristics such as high carrier mobility, high abundance in the Earth's crust, unique electronic structures, low carrier density and a highly anisotropic Fermi surface. These characteristics endow non-noble metals with potential roles in the specific applications of the LSPR effect. In addition, for non-noble metal materials, the specific mechanism by which the LSPR performance enhances the photocatalytic activity is examined, with a focus on theoretical analysis. The emphasis is on changing the types and sizes of nanoparticles to alter their macroscopic physical and chemical properties, enabling the plasmons to exhibit desired optical properties within a specific frequency range. At the same time, the existing evaluation criteria for the improvement in the photocatalytic performance by the LSPR effect are not perfect. It is desired to have a unified standard system and the adoption of test methods that are convenient for comparison. For example, light source calibration and light intensity measurement should be carried out to ensure consistent illumination conditions in photocatalytic experiments. The evaluation criteria for photocatalytic activity should be unified to ensure the comparability of data, such as degradation, hydrogen production and CO₂ reduction. The stability test procedures should be unified to ensure the durability of catalysts in practical applications.[Conclusions and Prospects] The mechanisms of using the Localized Surface Plasmon Resonance (LSPR) to modify the surface of TiO₂ and enhance its photocatalytic activity are summarized. Factors affecting the LSPR effect and the modification of the light absorption efficiency of TiO₂ are discussed. The complex multi-field synergistic effect is the result of the combined influence of multiple factors. Through appropriate modification, the absorption spectrum could have a red shift, improving the ability of TiO₂ to absorb visible light. However, currently, the research on enhancing the activity of TiO₂ by constructing plasmons mainly focuses on noble metals (such as Au, Ag, etc.), which are expensive for practical applications. A series of non-noble metals (transition metals, rare earth metals, main group metals) have been used to modify TiO₂ to construct plasmons through the LSPR effect, to improve the photocatalytic activity. The main mechanisms include the enhancement of the surrounding field effect caused by localized plasmons, the increase in the light scattering effect and the transfer of hot carriers from the metal to the semiconductor, which further increases the number of electron-hole pairs generated by the excitation of the semiconductor. The use of LSPR effect to modify the surface of TiO₂ is an effective means to improve the photocatalytic performance. Future research directions can be based on the LSPR effect, such as constructing Schottky junctions. By constructing specific plasmons and regulating their interfacial effects, the photocatalytic effects of a large class of semiconductor catalysts can be improved.

Key words: surface plasmon resonance; nano-titanium dioxide; photocatalytic performance; surface modification