Enhanced Photocatalytic CO₂ Reduction Over TiO₂ By Using Metalloporphyrin As The Cocatalyst

The effective use of solar energy is an important means to solve the energy crisis.The photocatalytic carbon dioxide reduction reaction can use solar energy to realize the conversion of CO₂into fuel and chemical raw materials,which can not only reduce the concentration of greenhouse gases in the atmosphere,but also realize the recycling of carbon resources.Therefore,the development of highly active and stable photocatalytic CO₂reduction materials is one of the current research hotspots.TiO₂material is widely used as a photocatalytic semiconductor.However,its poor adsorption capacity for CO₂gas and high internal photogenerated electron-hole recombination rate affect its photocatalytic CO₂reduction performance.In this paper,through the loading of metal porphyrin,the high-efficiency output of photocatalytic reduction products CO and CH₄is achieved.The specific research contents are as follows:we synthesized different metal porphyrin-loaded TiO₂photocatalytic reduction materials,and explored the photoreduction activity of the catalyst and the mechanism of its performance improvement.Through different characterization methods,it shows that metalloporphyrin is dispersed in molecular form,and forms a bonding bond with the surface of TiO₂through the terminal carboxyl group,without changing the structure and phase of the base TiO₂material.The mechanism analysis shows that the increased activity of the catalyst can be attributed to the introduction of the porphyrin ring metal center,which accelerates the photogenerated electron transport process,effectively reduces the photogenerated electron-hole pair recombination rate,and provides sites for CO₂adsorption and CO₂molecular activation plays a role in promoting;the unity of catalytic center and adsorption center has been successfully achieved.The best performance catalyst（TCPP-Cu@P25）has a reduction product yield of 35.8 times(13.6μmol g^-1h^-1)before loading,and it has good stability.It can still maintain 90%after three cycles of photocatalytic reduction experiments of activity.The experimental results of this paper fully prove the high efficiency and applicability of metal porphyrin as a cocatalyst,which provides a strategy and basis for the development of non-noble metal cocatalysts and the further application of porphyrin materials in the photocatalytic reduction of CO₂.