Researches On The Photocatalytic Performance Of Modified WO_3-xphotocatalysts

Since the Industrial Revolution,the carbon cycle of the ecosystem has gradually been broken owing to the massive combustion of fossil fuels,resulting in a sharp increase in the concentration of greenhouse gas and air pollutant,and the problem of greenhouse effect and energy crisis likewise become seriously.Therefore,in order to solve environmental problems and implement sustainable development strategies,solutions that can reduce green house gas emissions and air pollutant concentrations are urgently needed.As an environmentally friendly treatment of air pollution,solar driven photocatalytic reduction of CO₂ can reduce the concentration of CO₂ and conversion it into renewable energy,thereby alleviating the energy crisis and greenhouse effect.Literally,the development of photocatalytic technology is inseparable from the development of new photocatalysts.Therefore,the development of novel efficient semiconductor photocatalysts and in-depth exploration of their catalytic mechanisms have important practical significance and research value for the large-scale application of photocatalytic technology in large scale.Plasmonic semiconductor photocatalyst WO_3-x has attracted wide attention because of its high chemical stability,strong photon-harvesting ability and non-toxicity.In this thesis,by constructing WO_3-x with different concentration of oxygen vacancy,and depositing W₁₈O₄₉ with noble metal Au(Au-W₁₈O₄₉),the reasons and reaction mechanisms of their photocatalytic performance enhancement were explored,and the main research contents are as follows:Part Ⅰ:Photocatalytic performance of WO_3-xtowards NO oxidationIn this work,by calcining WO₃ under a reducing atmosphere,WO_3-x with different oxygen vacancy concentrations was constructed,and the effect of oxygen vacancy on photocatalytic oxidation of NO was explored.In this paper,tungsten chloride was used as a precursor to calcinate WO₃ under air atmosphere,and then mixed with different amounts of urea for calcination,so as to obtain WO_3-x with different oxygen vacancy concentrations.The results showed that:（1）When the urea was added to 5g,the prepared WO_3-x samples showed optimal photocatalytic NO oxidation activity,and the NO degradation rate reached to 43%,which was2 times higher than that of pristine WO₃（21%）.（2）The introduction of oxygen vacancies increases the number of reduced states in the system,and WO_3-xshows excellent localized surface plasma resonance（LSPR）effect,inducing more hot electrons injection and participating in photocatalytic oxidation of NO reactions.Part Ⅱ:Au-W₁₈O₄₉ photocatalytic CO₂ conversion to hydrocarbon fuelIn this section,photocatalytic semiconductors are modified by constructing composite photocatalysts.In this work,Au-W₁₈O₄₉ nanowires were prepared by mixing tungsten chloride and chloroauric acid as raw materials,and the effects of different Au source dosing amounts on the photocatalytic reduction of CO₂ performance of composite samples were explored.The results showed that:（1）5%Au-W₁₈O₄₉ had the best photocatalytic reduction CO₂ activity,and the CO₂ photorereaction rate reached 21.4μmol·g^-1·h^-1,which was 2.5 times higher than that of pristine W₁₈O₄₉(8.4μmol·g^-1·h^-1),with a CH₄ selectivity of 91%.（2）Noble metal Au as an electron radar can absorb more photons,and the dual LSPR effect of noble metal and W₁₈O₄₉successfully capture more photons,inducing stronger hot electrons injection participating in the reaction.