Study On The Preparation And Performance Of Plasmon-Enhanced Photocatalysts

Problems such as environmental pollution and the depletion of fossil energy have triggered an upsurge in countries all over the world seeking clean,high-efficiency renewable energy.Photocatalytic technology is an efficient and green way to obtain energy,but it still faces the main problems of low catalytic activity of catalysts and low solar energy conversion efficiency.Improving the separation ability of photogenerated carriers and inhibiting recombination is the key to solving this problem.The hot carriers,plasmon absorption,and localized plasmon electromagnetic field generated by the plasmon effect can effectively improve the photoelectric conversion efficiency of semiconductor materials.This dissertation takes wide-bandgap semiconductors as the research object,surface-modified titanium dioxide（TiO₂）by acid etching,composite precious metal gold with plasmon effect（Au/SrTiO₃）and semiconductor copper sulfide（p-Cu₇S₄/TiO₂）,etc.A plasmon heterojunction photocatalyst was constructed,and its photocatalytic properties for the conversion of nitrogen to ammonia and the reduction of carbon dioxide were studied.The details are as follows:（1）The Au/SrTiO₃nanoparticle composite photocatalyst was prepared by hydrothermal method and photochemistry.The plasmon resonance absorption of Au nanoparticles at 600nm can effectively broaden the spectral absorption range of SrTiO₃that only responds to ultraviolet light and improve its utilization of sunlight.The Au/SrTiO₃ composite photocatalyst exhibits enhanced photocatalytic nitrogen fixation performance under the optimized Au loading condition.（2）The p-Cu₇S₄/n-TiO₂ one-dimensional nanobelt p-n heterojunction photocatalyst was constructed by the physical oscillation method.Studies have found that the heterojunction catalyst can reduce CO₂ to CO,CH₄ and C₂H₆ under light conditions,and has a higher selectivity for C2 product ethylene in particular.In order to optimize the heterojunction,TiO₂ nanobelts were first prepared by hydrothermal method,and the surface was modified.The effect of different acid etching time on the surface structure of the nanobelts was explored.The results show that with the increase of the acid etching time,the morphology of the nanobelt changes greatly,the specific surface area increases,and a large number of tiny nanoparticles are produced on the surface.Nitrogen fixation performance test results show that the TiO₂ nanobelt prepared at the optimal acid etching time exhibits the best photocatalytic properties,and the surface-modified TiO₂nanobelt with a special structure can be used as an excellent carrier for constructing a heterojunction system.The ultra-thin Cu₇S₄ nanosheets were synthesized on a large scale by controlling the growth variable method.A high-resolution transmission electron microscope was used to systematically characterize and analyze the Cu₇S₄ nanosheets.The study found that Cu₇S₄nanosheets exhibit strong plasmon resonance absorption at 1500 nm.The photoelectrochemical test results show that Cu₇S₄ is a p-type semiconductor material with a band gap of 1.7 eV.Therefore,the prepared Cu₇S₄ nanosheet not only has a narrow band gap,but also has an excellent plasmon effect,which can fully utilize sunlight.