Preparation And Photocatalytic Performance Of Metal-oxide Hollow Sphere/Carbon Composite Photocatalysts

Absorbing solar energy and converting those into solar fuels for storage and utilization by semiconductor photocatalysts becomes the most promising solution to the growing global energy crisis and impact of fossil energy consumption on climate change.Therefore,it is necessary to design effective,low-cost,high stability photocatalyst to achieve this technical objective.Titanium dioxide?TiO₂?and zinc oxide?ZnO?are excellent semiconductor photocatalytic materials,but large band gap is and low quantum efficiency limited their application to a certain extent.The method employed in this paper is clean,simple and gentle,in which the unique electron transporting ability and the light absorption of visible-ultraviolet region by carbon material effectively improved the photoelectric properties and photocatalytic efficiency of semiconductor photocatalyst.Herein,a series of hybrid carbon materials@metal semiconductor hollow spherical materials exploited by this method.The catalytic performance and corresponding mechanism of photocatalytic reduction of carbon dioxide?CO₂?were investigated in this thesis.The main contents are listed as follows:?1?Firstly,carbon spheres were obtained by hydrothermal synthesis using glucose as carbon source.At room temperature,tetrabutyl titanate?TBOT?,the precursor of TiO₂,was encapsulated outside the carbon-sphere template by hydrolysis and condensation after aged for 12 h,and then the TiO₂ hollow sphere structure with different carbon content inside was fabricated by controlling the conditions of calcination?at different times?.This is a simple process,clean and pollution-free method,in which the intervention of carbon material can effectively improve the light absorption and conductivity of the photocatalyst,increase the specific surface area of the composite sample.Moreover,the?-?conjugation of the carbon material is very beneficial to the adsorption of reactant?CO₂?.The results of photocatalytic CO₂reduction show that composite hollow sphere samples with carbon materials are more effective than commercial titanium dioxide?P25?,duo to the presence of carbon core improves the efficiency of photocatalytic conversion of carbon dioxide and produces selectivity to products of photocatalytic reaction.Consequently,the carbon content of the optimal carbon@TiO₂ composite sample is about 7%.?2?ZnO is a promising photocatalyst with high conductivity and high quantum efficiency compare with TiO₂.Initially,the carbon-sphere template is also synthesized by glucose-solution hydrothermal method.And then,we add carbon spheres into zinc acetate solution for adsorption of Zn²⁺on carbon-sphere surface and aging.Eventually,ZnO hollow sphere structure containing different content of carbonaceous materials successfully synthesized by controlling the calcination conditions?different temperature?.The unique photoelectric properties of the carbon material optimize the optical absorption,conductivity,and CO₂ adsorption capacity of the composite photocatalyst.The results of photocatalytic experiments show that the carbon-ZnO composite photocatalyst effectively improves the efficiency of photocatalytic reduction of carbon dioxide relative to commercial ZnO.