The nitrogen oxides (NOx, including NO and NO2) in the atmosphere are one of the important precursors for the formation of secondary aerosols and have important contributions to the formation of haze in China. Therefore, the pollution control of nitrogen oxides is imminent. Nanophotocatalysis is a new interdisciplinary subject developed in recent years. With its characteristics of greenness, high efficiency, and low energy consumption, it exhibits broad application prospects in the field of environmental governance, and opens up new ideas especially for the deep treatment of atmospheric pollutants in low concentrations. .
The Environmental Pollution Control Team of the Institute of Earth Environment of the Chinese Academy of Sciences has made new progress in the photocatalytic degradation of NOx. In the early stage of semiconductor nanomaterials controllable construction and its catalytic performance of photocatalytic degradation of atmospheric pollutants (Applied Catalysis A: General. 2016, 515, 170. Industrial & Engineering Chemistry Research, 2016, 40, 10609), for the traditional single The limitations of phase-catalyzed materials have led to the design and development of a series of highly efficient nano-heterojunction photocatalytic materials that have been effectively applied to the degradation of NO contaminants in the atmosphere. Through the chemical composition of the material and micro-nano structure regulation, the “construction-effect†relationship between the structure composition of the catalytic material and NO removal in the photocatalytic process was explored to reveal its influence on the photocatalytic reaction mechanism. The relevant research results were published in Scientific Reports, Applied Catalysis B: Environmental, ACS Applied Materials & Interfaces and other international journals.
Compared with the intrinsic energy band structure of traditional single-phase catalytic materials, the construction of heterojunction catalytic materials can not only regulate the light absorption threshold of the materials, but also can realize the rapid separation of photocarriers and the reduction of electron holes by regulating the energy band structure. The degree of compounding increases the efficiency of photocatalytic degradation of pollutants. In addition, in the process of photocatalytic degradation of pollutants, the interfacial structure of the heterojunction determines the transfer and transport directions of the interface carrier, the adsorption characteristics of pollutants, and the reactivity of active groups. In view of this, the researchers of the research group used the Bi-based layered structure to facilitate the electron transfer characteristics, and based on (BiO)2CO3, in-situ thermal decomposition method was used to prepare α-Bi2O3/having good cycle stability and visible light activity. The (BiO)2CO3 heterojunction catalytic material greatly improves the separation efficiency of photogenerated carriers (Scientific Reports, 2016, 6, 23435). Subsequently, the researchers used g-C3N4 to sacrifice the provision of CO32-groups, through a one-step hydrothermal method to skillfully synthesize a controlled thickness of Bi2O2CO3/g-C3N4 layered heterojunction nanodisks (Figure 1). Through synergistic catalysis of morphology control and heterojunction, the effect of the heterojunction on the removal of NO is significantly enhanced. It has been found that superoxide radicals are the main active groups in the degradation of NO by this heterojunction. (Applied Catalysis B: Environmental , 2016, 199, 123). In addition, the new perovskite-type composite oxide has a greater structural tolerance due to the perovskite structure of ABO3, and its structure and performance are regulated to a greater extent. Therefore, LaFeO3-SrTiO3 (LFO-STO) heterojunction photocatalytic materials were prepared by controlling two perovskite materials with similar lattice structures. The experimental results and density functional theory (DFT) calculations show that the construction of the LFO-STO heterojunction forms a built-in electric field, the energy band position changes, and the interface optical carrier transfer and transmission have a new driving force, which is beneficial to light. The reaction process of catalytic degradation of pollutants (Figure 2) (Applied Catalysis B: Environmental, 2017, 204, 346). In addition, it has been found that nano-Ag can absorb visible light by surface plasmon resonance and transfer excited electrons to SrTiO 3 to form active oxygen radicals and increase the photocatalytic NO removal efficiency of SrTiO 3 under visible light (Figure 3). Nano-Ag loading and photocatalytic removal performance have a positive correlation within a certain range. By changing the Ag loading, the photocatalytic ability can be indirectly controlled. The existence of a surface basic site (Sr2+) is favorable for inhibiting the formation of NO2 (ACS Applied Materials & Interfaces, 2016, 8, 4165). In subsequent studies, it was found that the synthesized Bi/ZnWO4 photocatalytic material also has a similar plasma effect (ACS Sustainable Chemistry & Engineering, 2016, 4, 6912). This series of studies provides new ideas for designing highly efficient and selective nano photocatalytic materials.
The above research work has received support grants from the National Key R&D Program “Special Nanotechnology Projectsâ€, the “100-person Plan†of the Chinese Academy of Sciences and the National Natural Science Foundation.
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