Adjusting The Cocatalyst Of TiO₂-based Nanocomposites For Photocatalytic Reduction Of CO₂

Because of large amounts of fossil energy consumption,it produces a large amount of carbon dioxide which is not renewable,resulting in the the greenhouse effect and foreseeable energy crisis.To solve this problem,it is ideal to use carbon dioxide to reversely produce organic fuels.Given that the reaction itself is irreversible in mild conditions,we expect that the light of the sun can be used in the reactions to satisfy kinetics and thermodynamic requirements.Titanium oxide has become a hot material of photocatalytic reduction of carbon dioxide,due to the characters like cheap,non-toxic,good light stable and easy-preparation.Moreover,molybdenum sulfide,as a new type of semiconductor material,has been widely used as a cocatalyst owing to its stability,the product selectivity and excellent ability to transport the electron.Therefore,the separation of the carriers in the TiO2 under light and the production rate was promoted.The importance of cocatalyst arise our attention.(1)Tetrabutyl titanate and hydrofluoric acid was used to fabricate titanium oxide nanosheets by a hydrothermal technique.Then MoS2/TiO2 composite were synthesized by a same method.It was found that the maximum amount of CO2 was reduced to methol at a loading amout of 0.5%and its carrier separation efficiency was further confirmed by transient time-resolved PL decay measurements.The methanol conversion rate of molybdenum sulfide is much higher than that of platinum and gold in a aqueous solution under UV-vis light irradiation,while the catalytic selectivity of silver tends to reduce CO2 to acetaldehyde as main liquid production.(2)Nanocomposites consisting of a-MoS2 quantum dots,TiO2 nanoparticles and Co(OH)2 nanosheets as building blocks are successfully fabricated by a electrostatic self-assembly technique and using a molecular linker to link TiO2 nanoparticles and a-MoS2 quantum dots.The further separation of carries in the catalyst was confirmed by time-resolved fluorescence decay spectra.Therefore,in the gas phase photocatalytic reaction,carbon monoxide conversion efficiency of the a-MoS2/TiO2/Co(OH)2 was nearly twice that of TiO2/Co(OH)2 or a-MoS2/TiO2,while pure TiO2 has nearly no CO production.