Fabrication Of CuIn_0.3Ga_0.7S₂ Photocathode And Its Application On Photoelectrochemical CO₂ Reduction Reaction

With the increasing emission of atmospheric CO₂,the use of photocatalysis to convert CO₂ into usable chemicals and achieve the recycling of CO₂ has shown good prospects.Photocatalytic CO₂ reduction requires the use of photovoltaic materials to prepare suitable photoelectrodes.Copper indium gallium sulfide material is a direct bandgap p-type semiconductor material widely used as a light absorption layer in thin film solar cells.The band width of this material can be continuously adjusted from 1.6e V to 2.3 e V by adjusting the stoichiometric ratio of In/Ga atoms.This material can work stably in complex environments for a long time and can be used as a photocathode material in photocatalysis.Based on the large-scale deposition process,copper indium gallium sulfide thin films are generally prepared by physical vacuum deposition,which requires a large amount of energy to maintain high vacuum during the deposition process.From an economic and environmental perspective,this dissertation adopts the solution based nanocrystalline method to prepare Cu In_0.3Ga_0.7S₂ thin film as a photocathode.The use of n-hexane as an efficient surface ligand scavenger can yield large grain CIGS photocathode films,effectively improving the photocurrent density and repeatability of CIGS photocathodes.The CIGS photocathode is used for photocatalytic CO₂ reduction,and the exposed CIGS thin film photocathode has a limited CO₂ reduction activity,with the main reduction product being CO.In order to further improve the photoelectric CO₂ reduction performance of CIGS photocathodes,this dissertation improves the selectivity of CIGS photocathodes for CO₂ reduction by depositing gold nanoparticles catalyst on the surface of CIGS photocathodes.The CIGS thin film deposited with Au nanoparticles achieved a Faraday efficiency of 4%CO₂ reduction to CO in aqueous solution.In order to reduce the influence of aqueous solution on CO₂ reduction,this dissertation studied the photocatalytic CO₂ reduction performance of CIGS thin film in non-aqueous organic electrolytes.In a 0.1 M acetonitrile solution of tetrabutylammonium bromide,the CO₂reduction of the CIGS photocathode loaded with Au nanoparticles generated CO with a maximum Faradaic efficiency of 25%（-0.55 V vs FC/FC⁺）.In order to maximize the solubility of CO₂ in the electrolyte,this dissertation used imidazole based ionic liquids as the supporting electrolyte in acetonitrile and studied the CO₂ reduction performance of CIGS photocathodes in this electrolyte.Under bias voltage of-1 V vs FC/FC⁺,the main products of CO₂ reduction by CIGS photocathodes were CO and CH₄.By loading Cs Pb Br₃ perovskite nanocrystals on CIGS electrodes as catalysts for CO₂ reduction,it exhibits high CO₂ reduction selectivity.At the same time,the perovskite catalyst achieved a Faradaic efficiency of up to 84.8%for the conversion of CO₂ to CO in a 0.1 M 1-butyl-3-methylimidazolium tetrafluoroborate/acetonitrile electrolyte.In summary,this dissertation studied the photocatalytic CO₂ reduction reaction centered on CIGS photocathodes from three perspectives:electrode preparation,catalyst selection,and electrolyte engineering.The Faradaic efficiency of CO reduction in aqueous solution was increased from 4%to a maximum of 84.8%,and the selectivity of CIGS electrodes for CO₂ reduction was further improved,these demonstrate the broad application prospects of CIGS photocathodes in the photoelectric reduction of CO₂.