| Aggravated greenhouse effect caused by rapid consumption of fossil fuels andserious environmental pollution have restricted the development of economy and society.Photocatalysis has been considered as one of the promising strategies to solve the above problems.However,the high recombination rate of photogenerated electron-hole,low efficiency and poor stability of photocatalyst limited the application of photocatalysis.Therefore,it is greatly important to synthesize new photocatalysts with high efficiency and wide light spectrum response range.Herein,we chose tungsten oxides as a research target,which can be modified by crystal facet engineering,doping,defect engineering and heterojunction fabrication,respectively.We intended to study the relationship between crystal structure,morphology,energy band structure,and photocatalytic activity,photocatalytic mechanism.Our research findings may provide insights into the influence of application of photocatalysis.In summary,the main results are listed as follows:?1?This study demonstrated that hexagonal tungsten bronze M0.33WO3?M=K,Rb,Cs?series with{010}facets,prepared by solvothermal method,showed excellent full spectrum induced photocatalytic carbon dioxide reduction?PCR?performance directly from the air.According to the products of photocatalysis and density functional theory?DFT?study,some advanced characterization techniques,such as X-ray Fine Absorption Spectrum?EXAFS?,Synchrotron Radiation Vacuum Ultraviolet Photoionization Mass Spectrometry?SVUV-PIMS?,13C calibration experiment and X-ray photoelectron spectroscopy?XPS?have been applied to research the impact of photocatalys'micro structure,electronic structure on the mechanism of full spectrum photocatalytic CO2 reduction.Under full spectrum light irradiation,the samples Cs0.33WO3,Rb0.33WO3 and K0.33WO3 exhibited outstanding CH3OH production activity with the conversion rate of 4.375,3.775 and 1.925?mol gcat-11 h-1,respectively.While,under the irradiation of NIR light?>800 nm?,the samples Cs0.33WO3 and Rb0.33WO3 still exhibited good CH3OH production activity with the conversion rate of1.27 and 2.33?mol g-1cat h-1,respectively.More intriguing,the catalyst Rb0.33WO3 can be used continuously in a flowing air and still demonstrated nice performance.The results of TPD and theoretical calculations unveiled that the introduced alkali metal atom can enhance the selectively adsorb CO2 rather than O2 from the air and decrease the activation energy of CO2 reaction.Besides,in situ FT-IR indicated that W5+sites were possibly not only active for CO2 but also for H2O.The synergistic effect of the introduced alkali metal atom and W5+sites enhanced the activity of photocatalytic conversion of CO2 in air.In addition,the result DRS and ellipsometry confirmed that the NIR light induced PCR performance of M0.33WO3 series was mainly contributed by polaron transition induced by the short wavelength of NIR light.?2?This work prepared rich oxygen vacancies?OVs?WO3-x nanosheets with{001}facets using solvothermal synthesis of precursors and study the mechansims of photocatalytic nitrogen fixation.The WO3-x nanosheets exhibited superior photocatalytic performance for N2 fixtion to NH3 with the conversion rate of 82.41?mol h-1 g-1 under 420 nm light irridiation.Fourier Transform Infrared Spectroscopy?FT-IR?and Transmission Electron Microscope?TEM?confirmed that non-stoichiometry and two-dimensional structure of the WO3-x nanosheets induced the generation of OVs.In addition,the results of XPS and DRS unreviled that the N?N bond can be weakened and activated when electrons are transferred from photocatalyst into the anti-bonding?-orbitals of N2,facilitating the bond dissociation.This study provides new insights into the design of rich OVs photocatalyst for N2 fixtion.?3?This work synthesized a series of mace-like g-C3N4 decorated Cs0.33WO3nanocomposites using ultrasonic assisted strategy.The optimized g-C3N4@Cs0.33WO3?weight ratio=3:7?photocatalyst selectively converted low concentration methane?1000 ppm?into methanol with yield of 4.38?mol h-1 g-1 under full spectrum light irradiation.TEM and FT-IR indicated that the g-C3N4 anchored on the W-O bonding of the Cs0.33WO3.The·O2-firstly activated the methane to methyl on the surface of the g-C3N4 in the composite and then the photogenerated electrons from the Cs0.33WO3 in the composite inhibited the peroxidation and increased the generation of methanol.The strategy of components proportion regulating in the g-C3N4@Cs0.33WO3nanocomposites controlled the production of·O2-radical and photogenerated electrons,resulting in the effective and selective photocatalytic performance.?4?This work prepared Z-scheme g-C3N4@CsxWO3 nanocomposites via ultrasonic assisted strategy,exhibiting excellent UV isolating,visible light penetrating?70%?and NIR heat-shielding features.More importantly,these composites display excellent VOCs?HCHO or/and toluene?decomposing properties under the full spectrum light irradiation.Both electrochemical characterization and trapping experiments verified that the high efficiency of photocatalytic decomposing of VOCs by g-C3N4@CsxWO3nanocomposites depends on two sides:firstly,g-C3N4@CsxWO3 constructs a nice Z-scheme structure to promote the separation of charge carriers and then enhance photocatalytic oxidation effectively;secondly,the small polaron can jump from localized states to conduction band of CsxWO3 under irradiation of NIR and result in a NIR-catalytic reduction.Accoding to the above analyses,we found that Z-scheme g-C3N4@CsxWO3 nanocomposites can be applied as multifunctional smart windows coating.According to the study of synthesis and photocatalytic activity of tungsten oxides,this work provided theoretical basis and research ideas on the application of photocalysis technology on the field of clean energy production,green organic synthesis and environment purification. |
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