Study On The Preparation Of Bismuth Sulfide-based Heterojunction Materials And Their Photoelectrocalytic Reduction Of CO₂

Along with the rapid development of the global economy,the energy demands of human society have increased rapidly.The consumption of large amounts of non-renewable fossil fuels has caused excessive emissions of CO₂,that results serious greenhouse effect and environment issues of planet.Therefore,the carbon neutrality has become a common concern in the 21st century.As a clean,environmental friendly and sustainable renewable energy,solar energy is a direct or indirect energy source for the entire biological world.If the botanic photosynthesis can be mimicked,the excess CO₂ in the atmosphere can be converted into hydrocarbon fuels,realizing the recycling of carbon resources,and also alleviating the energy crisis and environmental problems.Photoelectrocatalytic CO₂ reduction is considered to be one of the effective pathways to produce high value-added hydrocarbon fuels.By selecting a semiconductor catalyst with a proper energy band structure as the photocathode or anode under a certain bias by the electrochemical workstation,a photoelectrocatalytic reduction system of CO₂is built,which can well simulate natural photosynthesis.In this paper,Bi₂S₃-based semiconductor materials with good properties for light absorption are selected to be study.In view of its drawbacks such as high photo-generated carrier recombination rate,semiconductors with suitable energy band are selected to prepare heterojunction composite materials,which exhibit improved efficiency for photoelectrocatalytic CO₂ reduction.(1)A series of CuWO₄@B_i2S₃-X/FTO heterojunction composite materials were prepared and appiled to the photoelectrocatalytic reduction of CO₂.Firstly,WO₃was in-situ grown on FTO by hydrothermal reaction.And CuWO₄/FTO electrode was obtained by reacting with copper nitrate at 550?in muffle furnace.Then Bi₂S₃nanosheets was deposited on the surface of CuWO₄/FTO by chemical bath deposition with annealing in argon atmosphere,resulting CuWO₄@Bi₂S₃-X/FTO photocathode.The cathode materials were characterized by a series of characterization and photoelectric investigations.The experiments of photoelectrocatalytic CO₂ reduction were carried out in KHCO₃ aqueous solution,with three electrode system under the external bias voltage and Xenon lamp irradiation.The experimental results indicated that the formation of heterojunction is beneficial to improve the separation of photogenerated carriers and the catalytic activity of photocathoes.The CuWO₄@Bi₂S₃-3 electrode exhibits the highest catalytic activity under-0.8 V(vs.SCE).The total yield of hydrocarbon fuels is 4 times higher than that of pure CuWO₄,and the C₂₊selectivity reaches up to 79%?(2)A series of CuS@Bi₂S₃ heterojunction composite materials were prepared and appiled to the photoelectrocatalytic reduction of CO₂.Firstly,Cu₂O nanocubes were used as templates to generate hollow CuS cubes through the Kirkendall effect.Then Bi(OH)₃nanosheets were in-situ grown on the surface of hollow CuS cubes.Finally a series of hollow CuS@Bi₂S₃ heterojunctions were prepared by the hydrothermal reaction.The experimental results showed that the formation of heterojunction not only increases the adsorption and activation sites of CO₂,but also helps to inhibit the recombination of photogeneratedcarriers,thereby improving the photoelectrocatalytic reduction of CO₂.The 5%-CuS@Bi₂S₃ electrode exhibits the highest catalytic activity under-0.5 V(vs.SCE).The total yield of hydrocarbon fuels is two times higher than that of pure CuS,and the selectivity of C₂₊products is about 70%.