Prepareration And Photocatalytic Properties Of Silvel-based Catalysts

With the rapid development of modern economy,the flourish of industrial civilization has brought off numerous conveniences,but also given rise to many serious problems,such as the greenhouse effect and the energy crisis.As a major component of greenhouse gases,CO₂ is constantly rising in the atmosphere,aggravating global sea-level rise and climate change which extremely threaten the survival of mankind.The fossil fuel stored on the earth is not renewable and human's over-exploitation has made it at the stage of exhaustion.The search for new alternative energy has become the focus of scientists.Because of its high energy density,environmental friendly and sustainable,solar energy is regarded as the most promising energy in the long run.Artificial photosynthesis can transform CO₂ into high value-added chemicals under mild conditions,such as CO,CH₄,C₂H₆,etc.,which can not only slow down the greenhouse effect,but also provide energy products to alleviate the energy shortage.Therefore,it has attracted scientific research personnel to investigate deeply on account of the promising application prospect.In this paper,different morphology of TiO₂ was loaded with Ag nanoparticles through the wet chemical reduction method to form silver matrix composite.By comparing photocatalytic effect,tablet-like TiO₂ templated by MIL-125?Ti?was selected to serve as the substrate for Ag loading.The synthesized Ag/TiO₂ composite photocatalyst is analysed through different means to characterize its physicochemical property.The reaction of photocatalytic CO₂ with H2O was performed to test its performance.The test results showed that the prepared tablet-likeTiO₂ was a mixed crystal material containing anatase and rutile,with uniform size and diameter of about 600 nm,on which surface many micropores and mesopores are.The Nanocomposite formed by Ag loading have a response to visible light to some extent,and shows good photocatalytic performance under simulated sunlight irradiation to convert CO₂ into CO and CH₄.By investigating the yield of TiO₂ with different content of Ag loading,it was found that the photocatalytic effect of composite materials first increased and then decreased with the increase of Ag loading.When the Ag loading was 1.0%,the yield of the products was the highest,and the yield of CO and CH₄ were 4.89 ?mol/g and 90.79 ?mol/g,respectively.Ag nanoparticles play a key role in the reaction by acting as the active site,activating the adsorbed CO₂ and promoting its transformation.In addition,the Ag/Ni-TiO₂ catalyst was further synthesized by doping metal into TiO₂ in order to improve the visible light catalytic performance of Ag matrix composites.The influence of Ni doping on the photocatalytic effect was investigated and numerous characterizations of the catalyst was carried out.Studies have shown that Ni doping builds impurity levels in the energy band structure of TiO₂,shifting the light absorption range to the visible region and further improving the photocatalytic efficiency.The photocatalytic effects of composite catalysts with different Ni doping amounts were investigated.It was found that the yield of photocatalytic reaction was the highest when the Ni doping amount was 0.5%.The yield of CO and CH₄ after 3 h illumination was 14.31 ?mol/g and 279.07 ?mol/g,respectively.Ni doping can accelerate the transfer of electrons to Ag nanoparticles by capturing electrons or holes to promote the electron-hole separation.Ag nanoparticles and Ni can jointly promote the photocatalytic reaction.Through the study in this paper,it can be seen that Ag,as a kind of novel metal with cheap price,can effectively enhance the adsorption and activation of CO₂ for TiO₂.At the same time,Ag nanoparticles can work together with doped transition metal Ni to further promote the reaction of photocatalytic CO₂ with H2O.The supported Ag-based photocatalytic materials have great application value.