Preparation Of TiO₂-based Materials And Their Photocatalytic CO₂ Reduction Performance

With the increasing fossil-fuel combustion and CO₂ emission,global energy crisis and green-house effect have caused great attentions.Photocatalytic CO₂reduction represents a clean,low-cost and environmentally friendly strategy for CO₂conversion into valuable hydrocarbon fuels by utilizing solar energy.This method can achieve the purpose of continuous recycling of carbon,saving energy and reducing environmental pollution.Therefore,it is of great academic significance and good potential in practical applications.Presently,the CO₂ energy conversion efficiency is usually low because carbon dioxide is a carbon-oxygen double bond configuration with very high bonding energy and stable structure,leading to the difficult activation.Meanwhile,the solubility of CO₂ in aqueous solution is very low.So,the adsorption of CO₂ on solid catalyst might be very poor.In addition,the traditional photocatalysts usually displayed low utilization of sunlight and high photoelectron-hole recombination due to low electroconductivity,leading to the poor photocatalytic quantum efficiency.So,the keystone is to design efficient catalysts to solve both the scientific problems in photocatalysis and enhance the CO₂ conversion efficiency.This work introduces metals into photocatalysts as co-catalysts,which could promote electron transfer,enhance the photoelectron-hole separation efficiency,and produce H atoms via photocatalytic water splitting,leading to the enhanced photocatalytic activity.More importantly,the metal co-catalyst could also promote the selectivity towards target products during CO₂ conversion.The reaching results are summarized as follows.(1)Core-shell structured TiO₂ has been successfully prepared by alcohol-thermal method without adding template,and the photocatalytic hydrogenation of CO₂ under mild conditions was realized.The core-shell structure can accelerate the mass transfer in the reaction.Meanwhile,the unique internal structure can improve the utilization rate of light via multiple light refractions.In addition,the larger surface area can promote the adsorption of reactant molecules.Furthermore,the nickel loaded on TiO₂can act as a co-catalyst,which can promote photoelectron transfer and thus,diminish the photoelectron-hole recombination,leading to the enhanced activity of photocatalytic CO₂ reduction.Besides,the electron-enriched nickel co-catalyst favors the formation of methane,corresponding to the high selectivity toward target product of methane during photocatalytic CO₂ reduction.(2)Nanoparticle TiO₂ around 5 nm was synthesized by alcohol-thermal method.Such a TiO₂ shows low photoelectron-hole recombination probability owing to the quantum size effect.Meanwhile,a larger specific surface area can facilitate the adsorption of reactant molecules.The Ru loaded on TiO₂ can construct Schottky potential barrier,which can effectively transfer photoelectrons and prevent the photoelectrons-hole recombination,leading to the enhanced catalytic activity.Meanwhile,the Ru co-catalyst also favors the formation of methane like Ni,leading to the high selectivity to methane during photocatalytic CO₂ reduction.