On March 9, 2022, Prof. Deng Bo of Wuhan Textile University (School of Materials/State Key Laboratory of New Materials and Advanced Processing Technology for Textiles) published his research results online in Applied Catalysis B: Environmental (IF=19.503) under the title “Amorphous TiO2 beats P25 in visible light photo-catalytic performance due to both total-internal-reflection boosted solar photothermal conversion and negative temperature coefficient of the forbidden bandwidth”. The first author is Prof. Deng Bo from Wuhan Textile University, and the first correspondent is Prof. Yang Huiyu, a Ph.D. student from the State Key Laboratory of New Textile Materials and Advanced Processing Technology, is the first author. The first corresponding author is Prof. Deng Bo from the School of Materials, and the first author is Yang Huiyu, a doctoral student trained by the National Key Laboratory of New Textile Materials and Advanced Processing Technology jointly established by the provincial ministry. The research results were supported by the National Natural Science Foundation of China.
Applied Catalysis B: Environment focuses on the application of the latest catalytic technology in the environment, and is the top international journal in this field. The published papers should not only have important theoretical guidance for the field of catalysis, but also have high application value, and at the same time be of wide scientific interest.
TiO2, as a semiconductor photocatalyst with excellent performance, can achieve a wide range of applications in wastewater treatment, air purification, sterilization and medical protection under the radiation of sunlight. Excellent photochemical stability, reactivity and no secondary pollution are the important manifestations of TiO2 in the field of environmental treatment for sustainable development, and it is also the most promising nano-functional material for high-efficiency energy saving and environmental protection applications at present.
The structure of TiO2 mainly contains two types of crystalline and amorphous. Among them, crystalline TiO2 (rutile and anatase) presents high catalytic activity under light excitation, but the industrial preparation is complicated, emits a lot of waste, and the crystalline transformation requires long-time high temperature (>500 oC) calcination and high energy consumption. Compared with crystalline TiO2, amorphous TiO2 has poor catalytic activity due to structural defects, but low energy consumption and simple preparation process. According to the classical physics theory, the forbidden band width of most semiconductors shows a negative correlation with temperature, i.e., the forbidden band width decreases with increasing temperature. Therefore, for the first time, the authors make full use of solar energy into thermal energy, and form SiO2@TiO2 core-shell catalysts with “egg”-like insulation structure by simple modification of amorphous TiO2, which can achieve the regulation of the forbidden band width by photothermal conversion efficiency and thus have high catalytic activity under visible light at room temperature.
Figure 1. Photothermal conversion enhancement mechanism of SiO2@TiO2-n visible photocatalyst.
The “eggshell” TiO2 of the SiO2@TiO2 core-shell catalyst is prepared by atomic layer deposition, and the deposited shell layer is highly dense and uniform, so that the incident light enters the interior of the “egg” and the light occurs at the “egg white”. The process is similar to the “greenhouse effect”, in which light is mostly absorbed and converted into heat by total reflection at the “egg white”. The refractive index of “eggshell” TiO2 is higher than that of “yolk” SiO2, and the isotropic nature of the amorphous phase ensures the feasibility of total reflection inside the “egg” structure. By depositing different thicknesses of “eggshell” TiO2, the photothermal conversion efficiency of the catalyst to total reflection light is improved and the photochemical activity is enhanced. The actual catalytic effect of SiO2@TiO2 core-shell catalysts with different “eggshell” thicknesses was verified with the model contaminant of refractory and highly toxic 17β-estradiol. The results showed that the catalytic degradation rate and removal rate of SiO2@TiO2 core-shell catalyst under visible light were 2.9 times and 1.5 times higher than those of commercial P25 (80 % anatase and 20 % rutile) with the thickness of “eggshell” TiO2 of about 32 nm, respectively. The optimal size of the core-shell structured catalyst is about 540 nm, which allows it to retain high catalytic activity while being easily recovered by low-speed centrifugation (500 rpm), avoiding secondary contamination and toxicity caused by conventional nanocatalysts that are difficult to recover.
Figure 2. Total reflection property and extremely strong photothermal conversion of SiO2@TiO2-n.
Prof. Deng Bo is a high-level overseas talent who was introduced from University of British Columbia in May 2016 to the School of Materials. He has been mainly engaged in the research related to the preparation of functionalized fabrics by atomic layer deposition and high-efficiency visible photocatalysts for several years after joining the university, the
