| Titanium dioxide(Ti O2) based semiconductor photocatalyst has received widespread attention as the most promising development photocatalytic material in the field of environmental pollution. However, the band gap of Ti O2 is large, only responding to ultraviolet light, the photo-generated carriers generated by light excitation can easily recombine, which limits its scope of application. In recent years, hydrogenated Ti O2(usually black, hence named as black Ti O2) has caused widespread concern of domestic and foreign scholars for its good visible responsive proporties. In this paper, black Ti O2 mesoporous nanospheres and inverse opals with morphology highly comparable to white Ti O2 can be obtained when selected white Ti O2 as precursor, and high-temperature heat treatment under H2 atmosphere; meanwhile, the catalytic activity was investigated by choosed methylene blue(MB) as model of organic pollutant. Within the scope of this paper, the main contents and conclusions are summarized as follows:(1) The preparation of self-supported black Ti O2 mesoporous nanosphere and photocatality performance under visible lightThe black Ti O2 mesoporous nanosphere was prepared at 500 oC for 2 h under H2 atmosphere, while selected the white anatase Ti O2 mesoporous nanosphere with good monodispersion as precursor. The results of field emission scanning electron microscope(FE-SEM), X-ray powder diffraction(XRD) and Raman spectroscopy show that black and white mesoporous Ti O2 nanosphere did not change significantly in macroscopic dimensions(diameter of about 385 nm), morphology(spherical) and the main crystalline(anatase). In the visible degradation process catalyzed by three catalysts(black Ti O2 mesoporous nanospheres, white Ti O2 mesoporous nanospheres and P25), black Ti O2 mesoporous nanosphere exhibited the highest catalytic activity when choosed MB as model of organic pollutant; the process of catalytic reaction demonstrated pseudo-first order kinetics rule, the value of relative standard deviation(RSD) about pseudo-first kinetic constants k is 2.45 %, and its catalytic activity did not significantly attenuate after repeated 10 times.(2) Fabrication of black Ti O2 inverse opals and photocatality performance under visible lightThe polystyrene(PS) beads were synthesized by free emulsion polymerization method, and PS template with opal structure was obtained after solvent evaporation self-assembly. Then titanium isopropoxide precursor was injected into the gap of PS pellets by forced injection method, and a large area of highly ordered white Ti O2 inverse opals was fabricated after calcination under high-temperature; black Ti O2 inverse opals was obtained in situ hydrotreatment against white Ti O2 inverse opals under H2 atmosphere. The visible photocatalytic activity and reusability of black Ti O2 inverse opals were investigated by selecting degradation of MB as model. Results showed that black Ti O2 inverse opals has the highest catalytic activity when referring to P25, white Ti O2 inverse opals, debris of black Ti O2 inverse opals. The process of catalytic reaction demonstrated pseudo-first order kinetics rule, the value of RSD about pseudo-first kinetic constants k is 6.61 %, and its catalytic activity did not significantly attenuate after repeated 10 times.(3) Verifing the existence of reducing species on the surface of black Ti O2To confirm the presence of reducing species on the surface of black Ti O2, we designed reaction between the resulting black Ti O2 mesoporous nanosphere and inverse opals and HAu Cl4 solution respectively; then selecting the original black Ti O2 mesoporous nanospheres and inverse opals as reference, choosing the reduction reaction of p-nitrophenol(4-NP) by Na BH4 generating p-aminophenol(4-AP) as example to verify the presence of species which can reduce HAu Cl4, and the reducing species was on the surface of black Ti O2 mesoporous nanospheres and inverse opals; The results of X-ray photoelectron spectroscopy(XPS) show that the resulting product of the reaction is Au NPs. |
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