Preparation Of Pervoskite Oxides And Their Performances In Photocatalytic Reduction Of CO₂ To Methyl Formate

The combustion of the fossil fuel has led to a sharp increase in CO2emission, andexcessive amount of CO2in the atmosphere has caused a series of environmental problems,which have attracted more and more attention in worldwide. CO2capture and sequestrationtechnology can store a large amount of CO2, but there is a leak risk along with environmentalhazards via the storage technology. Photocatalytic reduction of carbon dioxide is mild inreaction condition, friendly to environment and has many other advantages. In this paper, wehave investigated the photocatalytic reduction of CO2over SrTiO3perovskite catalysts inmethanol to form methyl formate. The main content is as following:1 Small size and well dispersed particles of Ag/SrTiO3and InOOH-SrTiO3semiconductors were prepared by solvothermal method by using oleic acid as a dispersant.The influences of the preparation method, mode of Ag loading, the Ag loading amount as wellas the InOOH composite amount on the photocatalytic activity have been studied.2 The catalysts were characterized by UV-vis DRS, XRD, TEM, HRTEM and FT-IR toobtain the structure, crystal morphology. The results of UV-vis DRS indicated that the lightabsorption of Ag/SrTiO3displayed a red-shift and a broader absorption wavelength, andInOOH loading also gave rise to the extension of UV light absorption range. XRD patternsshowed that Ag/SrTiO3photocatalyst was composed of SrTiO3and Ag in the form of cubicphase, and the average crystalline size was 14 nm. Meanwhile, InOOH-SrTiO3was composedof cubic phase SrTiO3coexisted with InOOH crystal, and the crystalline size was 21.5 nmcalculated from Scherrer formula. TEM photos showed that Ag nanoparticles were welldispersed on the surface of SrTiO3. Acting as electron trap, Ag atoms formed the electronicenrichment site of the catalyst system, promoted electron transfer, and enhanced thephotocatalytic activity. From HRTEM analysis the interface between InOOH and SrTiO3wasconjunct well, and regular heterojunction structure was formed as well. New conduction bandand valence band were formed in the heterojunction system and resulted in promoting thephotogenerated charge separation. The FT-IR spectra indicated that the synthesizedphotocatalysts were consisted of SrTiO3, Ag and InOOH nanoparticles.3 We used Ag/SrTiO3and InOOH-SrTiO3photocatalysts for photocatalyzing reductionof CO2to methyl formate in methanol, which was taken as the sacrifice reagent and reactant.Methanol consumed the photogenerated holes for facilitating the hole-electron separation andleading to the enhancement of CO2reduction. CO2was reduced to formic acid andformaldehyde, and then followed by the further reaction of formic acid, methanol andformaldehyde to methyl formate.