3D Bi@Sn₃O₄ Construction Of Photocatalytic Materials And Study On High Value-added Chemicals Produced By Photocatalytic Coupling

The global energy crisis and shortage has become a major problem facing mankind,and fossil fuels such as coal,oil and gas have been the most popular energy sources due to their competitive prices and availability.However,these feedstocks are the main cause of man-made carbon dioxide emissions,and these energy sources are non-renewable and are being depleted.Therefore,the exploration of alternative clean energy carriers with satisfactory efficiency is a topic worthy of attention.Solar energy has attracted particular attention because of its clean,environmentally friendly and sustainable resources.In terms of solar energy utilization,photocatalysis（PEC）powered by solar energy can be used to generate hydrogen peroxide（H₂O₂）,which provides a reliable research basis for rich clean energy development.H₂O₂ is a kind of high value-added chemical,which is characterized by multi-function and environmental protection,with the highest active oxygen content of green products.It has been used in a wide range of industrial fields,such as pulp and paper,textile bleaching,chemical synthesis,water treatment and disinfection.However,the main method of producing H₂O₂,anthraquinone oxidation,consumes a lot of energy and resources,and causes serious pollution to the environment.The photocatalytic route for H₂O₂ production is particularly attractive because the entire process involves only water,O₂,solar energy,and electricity.Based on the matching of matter and energy,the photochemical cell coupling system can successfully integrate the reduction reaction of cathode with the oxidation reaction of anode.It can not only be used for catalytic production of various energy sources,but also realize the recovery of pollutants cooperatively.Therefore,Sn₃O₄ and Bi@Sn₃O₄ photocatalytic materials were designed and prepared in this paper for H₂O₂ production,and WS₂ photocatalytic materials with three-dimensional flower-like structure were used for H₂S and S^2-pollutant recovery.Build Bi@Sn₃O₄||Sn₃O₄ photoelectrochemical cell used in the anode and cathode produce H₂O₂,build the Bi@Sn₃O₄||WS₂ photoelectrochemical cell coupling recycle sulfur powder used for producing H₂O₂.The main research contents of this paper are as follows:（1）Sn₃O₄ microsphere integrated electrode was synthesized by hydrothermal method on nickel foam.Bi metal was deposited on Sn₃O₄ microsphere surface by electrodeposition method,and 3D Bi@Sn₃O₄ Schottky junction photocatalytic integrated photocathode electrode with oxygen vacancy was constructed.The excellent photocatalytic performance of Bi@Sn₃O₄ composites has been demonstrated by a series of opto-electrical experiments.The introduction of metal Bi plasmon resonance effect（SPR）can improve the visible light absorption efficiency of Bi@Sn₃O₄ photocatalyst,improve the transfer efficiency of photogenerated electrons,and promote the efficient production of H₂O₂by oxygen reduction（ORR）.Oxygen vacancies as electron traps can increase the concentration of carriers and accelerate the separation of photo-generated carriers.Using Bi@Sn₃O₄ Schottky-junction photocatalytic material as a photocathode for the production of H₂O₂ in ORR,the H₂O₂ yield was 1.4 mmol/L within 2 hours under visible light irradiation and-0.7V（vs.Ag/AgCl）external bias（pH=10.5,0.1 mol/L Na₂SO₄）.Faraday efficiency reached 75.73%.The results of free radical trapping experiment and rotating disk test show that Bi@Sn₃O₄ exists two step single electron pathway and one step two electron pathway in the production of H₂O₂by ORR.Sn₃O₄ microspheres showed excellent photocatalytic performance for the production of H₂O₂ by water oxidation（WOR）.Under visible light irradiation and 1.4V（vs.Ag/AgCl）external bias（0.1 mol/L KOH）,the production of H₂O₂ reached 150μmol/L within 2h.Using Bi@Sn₃O₄ as the photocathode and Sn₃O₄ as the photoanode,the photochemical cell can produce H₂O₂ simultaneously at the cathode and anode at-0.8 V（vs.Ag/AgCl）voltage,and the total output of H₂O₂ is 1.33 mmol/L.This study provides a reference value for the construction of a new type of battery system with anode WOR producing H₂O₂ coupled cathode ORR producing H₂O₂.（2）The photocatalytic materials of WS₂ with three-dimensional flower-like structure were successfully prepared by hydrothermal method.The flower-like structure of WS₂ increases the contact area of photocatalytic reaction,increases the active site,and has high oxidation activity for S^2-.Contact Angle experiments show that WS₂ has a low chemical affinity for sulfur elements of S^2-oxidation products.The desulfurization characteristics of WS₂ can avoid passivation caused by solid sulfur deposition and realize long-term self-cleaning desulfurization.Electrochemical tests show that flower WS₂ has excellent photocatalytic performance for alkaline sulfur oxidation reaction（SOR）,and can reach 50 mA current density at a voltage of-0.3V（vs.Ag/AgCl）,and long-term SOR has good stability.The catalytic performance of alkaline ORR excellent photoelectric Bi@Sn₃O₄ as a system of the photocathode,WS₂as light anode system,build the Bi@Sn₃O₄||WS₂ alkaline photoelectrochemical cell,through the coupling ORR and SOR,can promote the H₂O₂ production,The photoelectric chemical recovery of sulfur powder and production of H₂O₂ can be achieved simultaneously with low energy consumption.The self-cleaning WS₂ and the high efficiency Bi@Sn₃O₄ can significantly improve the energy efficiency.The alkaline photochemical cell shows excellent stability within 10 hours,and the total amount of H₂O₂ generated within 10 hours is about 5 mmol/L,and the total production of sulfur powder is about 81 mg.This study provides a reference value for the construction of a novel sulfide recovery coupled with the production of H₂O₂ battery system.