Research On Photo (electric) Catalytic Reduction Of Carbon Dioxide To Produce Carbon-compounds

The arrival of the industrial era is accompanied by the sharp consumption of fossil fuels.The global warming caused by the massive emission of carbon dioxide has become one of the environmental problems that human beings need to solve.To alleviate this impact,carbon dioxide emission reduction,conversion,storage and capture it has gradually become a hot issue in recent years.The traditional method has limitations on the conversion of carbon dioxide,such as harsh reaction conditions,high reaction energy consumption and low conversion efficiency.The semiconductor catalyst uses solar energy to simulate the photosynthesis of green plants,and converts inexpensive and abundant carbon dioxide and water into high value-added products such as hydrocarbons and syngas under normal temperature and normal pressure conditions.This consumes carbon dioxide,reduces the concentration of carbon dioxide in the air,and effectively alleviates the global energy crisis,making carbon dioxide resources and bringing huge economic benefits.Therefore,photocatalytic conversion of carbon dioxide has important research significance and application prospects for environmental and energy issues.However,photocatalytic semiconductors generally have problems such as narrow light absorption range and high recombination ratio of photogenerated electrons and holes.In order to solve these problems,techniques such as ion doping,semiconductor recombination,and metal modification are generally employed.In addition,photoelectrocatalysis,as a basis of photocatalysis,promotes the separation of electrons and holes to a large extent by applying a small bias voltage,thereby improving the catalytic efficiency.In this article,our main research contents are as follows:?1?The titanium dioxide nanotube array electrode sheet was synthesized by simple anodization method,and barium titanate was supported on the inner and outer walls of the tube by hydrothermal method,and the heterojunction of the core-shell structure was applied to the photoanode-driven photoelectrocatalytic system.The anode material is biased to excite electrons to the cathode copper foam under the excitation of ultraviolet light,and the CO₂ in the solution is reduced and converted to formic acid by utilizing the large specific surface area of the copper foam and the selectivity for CO₂ reduction.Through the modulation of the properties of the anode material,the influence of the anode material on the activity of the reduction product and the deep investigation of the cathode reduction process were explored.?2?Using a simple impregnation method,NaOH and?NH₄?₂S₂O₆ were used as precursor liquids,firstly Cu?OH?₂ nanowires were grown on the copper foam substrate,and then Cu₂O nanowire electrode sheets were obtained by firing in argon gas.Due to the severe photo-corrosion phenomenon of Cu₂O,the passivation layer of Al₂O₃ on the synthesized Cu₂O nanowire electrode sheet is applied as a photocathode to the photocatalytic reaction,which prolongs the life and stability of the catalyst.On the one hand,Cu₂O has a narrow band gap??2.2eV?,which can absorb a large amount of visible light and has good selectivity to CO₂.On the other hand,as a P-type semiconductor,Cu₂O mainly uses electron conduction as the main route.The application of negative bias voltage makes the bending of the energy band in the solution beneficial to the conduction of electrons to the material interface to reduce CO₂,which can greatly improve the photocatalytic efficiency.?3?Based on the conclusions in the second part of the work,Cu₂O has better CO₂catalytic activity.However,since hydrogen production as a competitive reaction greatly inhibits the catalytic efficiency during the progress of the reduction reaction.Then we used a simple hot solvent method to synthesize C-coated Cu₂O particles by carbonizing the MOF of the synthesized metal Cu and used it as a catalyst to reduce CO₂ by visible light.And the amino functional modification on the surface of the material enhances the selectivity of photocatalytic CO₂ reduction,and effectively inhibits hydrogen production based on the improvement of catalytic efficiency.