| Water pollution and air pollution is not only the damage to the ecological environment,but also is the threat to human health,and the main pollution is the result of emissions of dyed wastewater and volatile organic compounds(VOCs).A new type,high efficiency and low cost processing technology for the management of the liquid phase and gas phase organic pollutants is urgently needed.Semiconductor photodegradation technology is considered to be an effective way to solve the problem of environmental governance.Nano Ti O2 and Zn O is the popular photocatalyst which is with similar band gap,non-toxic,wide distribution,etc.But for now,it still exists a lot of problems for nano Ti O2 and Zn O photocatalyst such as low photocatalytic efficiency,only UV excitation,quick deactivation etc.,which restricts their wide application.In order to solve these problems,in this paper,we explore new methods to increase the photocatalytic activity and durability,broaden the light response range by controlling the microstructure of nano Ti O2 and Zn O,the effect of the interaction between reactant and nano Ti O2,the synergetic effect of photothermocatalytic and light driven catalytic by Pt surface plasmonic effects.The main results in this study can be summarized as follows:1.we developed a novel strategy conceptually different from the Kirkendall effect to prepare Ti O2 nanocrystals with internal pores,and its photocatalytic activity is higher than Ti O2 solid nanocrystals.Ti O2 nanocrystals with internal pores were prepared by a microwave-assisted hydrolysis of Ti OCl2 aqueous solution in the presence of HF followed by calcination.The Ti O2 nanocrystals with internal pores are the pure anatase structures.There is one or more mesopores existed in each of Ti O2 particles,and the pores observed by TEM are inside the nanoparticles,not on the surface.HF and calcination plays a crucial role in the formation of Ti O2 nanocrystals with internal pores and crystalline phase.The Ti O2 nanocrystals with internal pores exhibit higher photocatalytic activity for photodegradation of cationic dye crystal violet(CV),anionic dye methyl orange(MO)and nonionic organic pollutants 4-chlorophenol(4-CP),compared to the fluorinated Ti O2 solid nanocrystals.The reason is the higher e-h separation efficiency of the Ti O2 nanocrystals with internal pores than the fluorinated Ti O2 solid nanocrystals due to the thinner wall thickness of the Ti O2 nanocrystals with internal pores,which leads to the faster migration of the photoexcited electrons and holes from the internal to surface.2.We studied the pivotal effect of the interaction between reactant and anatase Ti O2 nanosheets with exposed {001} facets on photocatalysis.It is found that for the photodegradation of acetone and benzene,the strong interaction not only reverses the photocatalytic activity of the F-free Ti O2 nanosheets and F-modified Ti O2 nanosheets,but also conspicuously induces efficient visible photocatalytic activity.From the measured photocurrent,we found the strong interaction between acetone and Fmodified Ti O2 nanosheets,and the strong interaction between benzene and F-free Ti O2 nanosheets can increase e-h separation efficiency.Through the DRUV-Vis spectra,it is attributed to the enhancement of the visible absorption above 420 nm after the adsorption of acetone on TNS-F and the adsorption of benzene on TNS.From the results of the fluorescence emission decay,when the atmosphere changes from air to acetone vapor,the ?uorescence lifetime of both TNS-F and TNS almost remains unchanged.TNS-F has a ?uorescence lifetime longer than the TNS in acetone vapor.But when the atmosphere changes from air to benzene vapor,the ?uorescence lifetime of TNS increases longer than that of TNS-F.The interaction between reactant and Ti O2 was theoretically investigated by density functional theory(DFT)calculation.The adsorption energy of acetone on F-modified Ti O2 slab is lower than that of acetone on F-free Ti O2 slab.And the length of O=C bond in acetone becomes longer.The adsorption of acetone on the F-modified Ti O2 slab leads to a decrease of band gap.For benzene adsorption,the lower adsorption energy of F-free Ti O2 than Fmodified Ti O2,and the adsorption of benzene on F-free Ti O2 slab leads to a decrease of their band gap.3.We found using the synergetic effect of photothermocatalytic can highly improve the activity effciency of anatase Ti O2 nanosheets with exposed {001} facets on the degradation of benzene.Through the benzene oxidation on Ti O2 nanosheets at different temperatures,we conclude that with the increase of the temperature,the photothermocatalytic activity for the oxidation of benzene increases,the photocurrent decreases.The CO2 production rate of the photothermocatalytic oxidation for benzene is much higher than the summation of the photocatalytic rate and the thermocatalytic rate at the same temperature.So the photocatalytic oxidation is not simplely in parallel with the thermocatalytic oxidation independently proceeds.There must be a synergetic effect between the photocatalytic and thermocatalytic oxidation did exist in the photothermocatalytic oxidation.The photothermocatalytic synergetic effect is further verified by in-situ FTIR spectra with CO as probe molecule: active speciesproduced by photogenerated electrons and holes accelerate the thermocatalytic oxidation on the Ti O2 nanosheets,thus signi?cantly increasing the catalytic activity.By coating Ti O2 nanosheets on an Hg lamp,we realize highly efficient synergetic photothermocatalytic without using additional heater,which exhibiting excellent durability.4.Zinc carbonate hydroxide nanobelts are prepared by the hydrolysis of zinc acetate aqueous solution in the presence of urea,and then the calcination of the zinc carbonate hydroxide nanobelts results in the formation of Zn O nanowires.Zn O nanowires were the long chains of closely attached Zn O nanocrystals with Zn O/Zn O nanocrystal junctions.Compared to Zn O nanocrystals,Zn O nanowires exhibit higher photoresponse current(~ m A)and superior on/off current ratio(~ 1000).Steadystate photoluminescence shows the Zn O nanowires have lower concentration of defects as recombination centers,which reveals that upon UV irradiation,more photogenerated charge carriers could migrate from the bulk to the surface,resulting in its higher separation efficiency of photogenerated electrons and holes.The Zn O nanowires have a longer ?uorescence lifetime than the Zn O nanocrystals,suggesting that the photogenerated electrons and holes in the former have more probability to migrate to the electrode than those in the latter.The impedance of the two Zn O samples indicates that the resistance of the Zn O nanowires is much smaller than that of the Zn O nanocrystals,which is favorable to the migration of the photogenerated charge carriers.5.1.0 wt% Pt/Zn O and 1.0 wt% Pt/Ti O2 were prepared by the impregnation of Zn O or Ti O2 nanosheets with Pt(NO3)2 aqueous solution,followed by the reduction with Na BH4 aqueous solution.UV-Vis-IR spectra test reveals that Pt/Zn O and Pt/Ti O2 show absorption in the entire solar spectrum region.The benzene oxidation test suggests that the deposition of Pt on Zn O or Ti O2 nanosheets can significantly improve the photocatalytic efficiency: under the irradiation of the Xe lamp,the CO2 production rate of 1.0 wt% Pt/Zn O(r Pt/Zn O=10.17 μmol min-1 g-1)is 59.8 times higher than r Zn O;1.0 wt% Pt/Ti O2 exhibit excellent catalytic activity,r Pt/Ti O2(428.61 μmol min-1g-1)is 2381.2 times higher than r Ti O2,and 42.1 times higher than r Pt/Zn O,besides1.0 wt% Pt/Ti O2 exhibit good durability.Under the irradiation of Vis-IR above 420,480,560 and 690 nm,1.0 wt% Pt/Ti O2 still has high catalytic activity. |
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