Preparation Of Semiconductor Materials Based On TiO₂ And Study On Photocatalytic CO₂ Fixation

The greenhouse effect caused by CO2,a greenhouse gas,has a great threat on people's life.The increasing content of CO2 in the atmosphere and the consumption of fossil energy has attracted more and more attention.The photocatalytic reduction of CO2 can not only reduce the CO2 content in the atmosphere,but also convert CO2 into high value-added fuel and chemical raw materials,such as CH4,CO and C2H6.The resources of solar energy and CO2 can be fully utilized and due to the green environmental protection,the photocatalytic reduction of CO2 has great prospect of research value and application.In our study,Pd/TiO2 catalyst was prepared by glucose reduction method and used in photocatalytic CO2 hydrogenation to evaluate its performance.The results showed that the yields of CH4,CO and C2H6 increased with the increase of reaction time,and the loading of Pd could effectively promote the reaction.With the increase of Pd content,the reaction activity increased first and then decreased.The 1.0%Pd/TiO2 catalyst showed the highest activity and the yields of CH4,CO and C2H5 were reached to 355,62,46.35 and 39.69 ?mol/g,respectively under UV irradiation(?<400nm)for 3h.The enhanced reactivity is attributed to the synergetic effect of Pd and TiO2.Pd nanoparticles can aggregate electrons and form electron accumulation centers.On the one hand,electrons and holes are effectively separated to improve the reaction performance.On the other hand,Pd can be used as reactive sites to adsorb and activate CO2 molecules,further promoting the photocatalytic activity of CO2 hydrogenation effectively.In addition,Ce-doped TiO2 catalysts were prepared by sol-gel method,and Pd was loaded on the surface by glucose reduction method.The catalysts were used for photocatalytic CO2 hydrogenation to evaluate its performance.The results showed that the doping of Ce is beneficial to the increase of the reactivity.With the increase of Ce doping content,the reactivity increased firstly and then decreased.The 0.5%Ce-doped TiO2 catalyst(1.0%Pd)showed the best activity and the yields of CH4 and CO were 220.61 and 27.36 ?mol/g,respectively under visible light(400nm<?<760nm)for 3h.The formed impurity energy level by Ce doping can extend the photoresponse range of TiO2 to the visible region.Ce element exists in two valence states of Ce3+ and Ce4+,and the conversion between these two valences is beneficial to the separation of charge.The Pd as a cocatalyst,can absorb and activate CO2 and provide reactive sites to facilitate the reaction efficiency.