| The reduction of CO2 via artificial photosynthesis is considered as a green and sustainable way to produce solar fuels through resource utilization of CO2.The photocatalytic CO2 reduction system consists of three basic elements:photosensitizer,catalyst and sacrificial electron donor,in which,the catalyst is the key component for mediating CO2 reduction.Numerious metal complexes had been described to catalyze CO2reduction under photochemical conditions,however,most of them contain precious metals（Ru,Ir,Re,etc）and suffered from complicated synthesis and poor stability in photocatalysis.In this regard,the development of novel earth-abundent metal-based catalysts with high activity and stability as well simple preparation is highly desired.In this thesis,two novel SiO2-supported hybrid catalysts,SiO2-NH2-Co and SiO2-TPA-Co,were synthesized as catalysts for photocatalytic CO2 reduction in the presence of g-C3N4as photosensitizer and triethylamine as sacrificial electron donor.The results were obtained as following:（1）The SiO2-NH2-Co was prepared by coordinating of Co2+with aminated SiO2nanoparticles（SiO2-NH2）.The SiO2-NH2-Co was characterized by IR spectra,solid UV-vis spectra,XPS,SEM,TEM,and ICP-MS.A photocatalytic CO2 reduction system were constructed by using SiO2-NH2-Co as catalyst,g-C3N4 as photosensitizer and TEA as sacrificial electron donor in CO2-saturated CH3CN/H2O mixed solvet.The system enabled to produce CO and H2 as syngas under visible light irradiation.At optimized conditions,the system demonstrated excellent stability for syngas production,the total amount of syngas of 5053μmol.g-1with a CO/H2 ratio of 1:1 were obtained after 140 hours of irradiation.The amino groups coordinated CoII-complex on the surface of SiO2 with a plausible structure of[Co（NH2）4Cl2]is proposed as a major active species for mediating CO2-to-CO and H+-to-H2 conversions.（2）The SiO2-TPA-Co hybrid catalyst,prepared by covalently bonding TPA ligand onto the surface of SiO2,were synthesized.The SiO2-TPA-Co were chareacterized by IR spectra,solid UV-vis spectra,XPS,SEM,TEM,ICP-MS,and solid 1H NMR.A photocatalytic CO2 reduction system consists of SiO2-NH2-Co as catalyst,g-C3N4 as photosensitizer and TEA as sacrificial electron donor in CO2-saturated CH3CN/H2O mixed solvet were construted.Under visible-light irradiation,the system enabled to produce CO and H2 as syngas.At optimized conditions,the system produced syngas with a total amount of 10179μmol.g-1with a CO/H2 ratio of 1:1 after 160 hours of irradiation.The system exhibited high acitivty and stability for syngas production. |
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