The Synthesis And Study On Photo-thermal Catalytic Properties Of Mesoporous WO_3-x Catalysts

Frequent human activities as well as the energy demand is rising, the rise in emissions of carbon dioxide, the greenhouse effect caused by rising, prompting human find all sorts of ways to reduce the amount of CO2 in the atmosphere. Which employ photocatalytic technology synthetic hydrocarbon catalytic reduction of CO2 can realize the cycle of carbon and energy supplying. Due to low conversion efficiency hinders its development and application in industrial production, thus to find efficient catalytic material, improve the energy conversion efficiency of catalytic reaction is the key to the catalytic reduction of CO2. In numerous catalytic materials, mesoporous nanometer catalytic material with large specific surface area, strong adsorption capacity, more active center of macroscopic materials; In photo-splitting water hydrogen production, catalytic CO2 reduction etc are shows excellent catalytic performance, is a development potential and application prospect of catalytic materials. In this paper, we use the hard template synthesis of different shape and aperture size of mesoporous WO₃ catalytic reduction of CO2 in the coupling of field conditions. However oxygen vacancy is the origin of the tungsten trioxide induced catalytic performance, the oxygen vacancy will help to produce more of the catalyst surface defects, because of the existence of trap effect, accelerate the light on the surface of the electron transfer rate, as well as to the CO2 reduction into C/CO, thus improve the tungsten trioxide catalytic reduction of carbon dioxide generated hydrocarbons. Specific research work and achievements include the following parts:1. The synthesis and study on photo-thermal catalytic properties of oxygen vacancy mesoporous WO_3-x catalystsWe used the mesoporous silica molecular sieve ?K.IT-6? as hard template, silicotungstic acid hydrate as the preparation of tungsten trioxide as precursors, let stand, solvent double solvent method and solid roasting successful synthesis of the three dimensional ordered mesoporous tungsten oxide. Studies have shown that the m-WO₃ has large specific surface and entrance, effectively increase the catalytic reactivity; Mesoporous tungsten trioxide ordered pore structure, high crystallinity, greatly reduces the light electronic-hole of the compound, so as to promote the performance of the thermal coupling catalytic reduction of CO2. H2 heat treatment at different temperatures of the band gap of m-WO₃ catalysts can be reduced from 2.76 eV to 2.31 eV, catalyst redshift phenomenon is obvious. As the H2 heat treatment temperature rising, producing oxygen vacancy concentration will effectively improve thermal coupling catalytic reduction of CO2 generated hydrocarbons.2. The synthesis and study on photo-thermal catalytic properties of oxygen vacancy mesoporous WO_3-x loading nanometer molybdenum catalystsWith different morphology of the KIT-6 as hard template, using the ultrasonic double solvent method synthesized by different morphology of the mesoporous WO₃. Mo can effectively reduce the m-WO_3-x loading nanoparticles of band gap, but also become the light electronic capture center, promote normal living carrier of separation. Thermal catalytic CO2 and H2O generated CH4 and CH3OH experiments show that under the condition of thermal coupling, m-Mo/WO_3-x has good catalytic performance CO2 reduction to generate methane and methanol. Good catalytic activity of field due to the formation of oxygen vacancies, nanometer metal and mesoporous structure can promote the activity of CO2 reduction. In addition, compared with the microstructure has a larger surface area, and is conducive to the charge transfer to the surface and lead to higher emissions reduction activities.3. The synthesis and study on photo-thermal catalytic properties of inverse opal structure of WO₃ catalystsVertical sedimentary self-assembly adopted in the experiment of PMMA prepared by ball is a relatively simple operation. In the preparation of PMMA template control of MMA content can control gel ball size, to control the aperture of the inverse opal structure. Different diameter of 3DOM-WO₃ by partial of the precursor solution of ammonium tungstate colloidal crystal template was prepared.3DOM-WO₃ catalyst surface load of field Au by illumination successful synthesis, structure stability of the catalyst and gold nanoparticles deposited on the inner wall surface high dispersion, uniform size. Inverse opal structure light effect can improve the radiation from the sun and ordered macroporous absorption efficiency the spread of the reactant molecules. In addition, gold nanoparticles deposition in WO₃ surface can absorb more visible and induction of gold nanoparticles enhance SPR effect excited electrons WO₃ catalytic CO2 to CH4.3DOM-Au/WO₃ catalysts exhibited good catalytic reduction of field performance of CO2 and H2O to produce hydrocarbons.3DOM-WO₃ catalysts of field load Au nanoparticles may support metal coordination effect of basic research and potential practical applications.4. The synthesis and study on photo-thermal catalytic properties of large pore size mesoporous WO₃ catalystsWith different morphologies as a hard template reaming of SiO₂, silicotungstic acid hydrate as the preparation of tungsten trioxide as precursors. The tungsten trioxide is introduced into the reamer silica microspheres pores, calcined in an air atmosphere, the resulting load WO₃ mesoporous silica microspheres with HF solution to remove the mesoporous silica that was large pore mesoporous WO₃ microspheres. Resulting mesoporous WO₃ microspheres aperture up to 4.5nm, and the preparation method is simple, room temperature. Ordered pore structure, high specific surface area and a high degree of crystallinity, reducing electronic light green-hole pair recombination, promote solar thermal catalytic reduction of CO2 generated hydrocarbons.