3D WO₃@Co₂SnO₄Z-Type Heterojunctions Preparation And Study On Photoelectrocatalytic Performance For H₂O₂ Production

With the rapid development of social economy and the continuous improvement of human living standards,energy shortage and environmental pollution have gradually become the two major problems that hinder the development and progress.Therefore,it is significant to seek sustainable clean energy and green ecofriendly functional materials.Solar energy as a kind of environment-friendly energy,its conversion into other available energy is the key to solve the problem of energy shortage.As a new technology of utilizing solar energy,photoelectrocatalytic（PEC）is not only used for catalytic production of energy,but also for degradation of water pollutants to solve energy and environmental problems.Hydrogen peroxide（H₂O₂）as an environmentally friendly chemical,is widely used in pulp and fabric bleaching,chemical raw material synthesis,electronic manufacturing,water purification and other fields.Therefore,the efficient synthesis of H₂O₂ has attracted much attention in recent years.The photoelectrocatalytic 2e^-oxygen reduction（ORR）and 2e^-water oxidation（WOR）method driven by solar energy has the advantages of in-situ production,mild reaction conditions and no secondary pollution.This is a new technology for H₂O₂ production.However,due to the low light utilization and low charge transfer efficiency and the low selectivity for 2e^-ORR and 2e^-WOR of catalyst limit the efficiency of PEC system in the production H₂O₂.Therefore,the selection of photoelectrocatalytic materials is very important,and the construction of a novel,efficient,visible light-responsive semiconductor photoelectrocatalytic materials is the key of this technology.Therefore,in this paper prepared a 3D WO₃@Co₂SnO₄ Z-type heterojunction photocathode photoelectrocatalytic material for the production of H₂O₂and in-situ degradation pollutants,and 3D WO₃@Co₂SnO₄ coupled with a Fe₂O₃-Ti photoanode bi-directional photoelectrocatalytic production of H₂O₂.The research content of this paper is as follows:（1）3D WO₃@Co₂SnO₄ Z-type heterojunction photoelectrocatalytic material was prepared by method of hydrothermal followed by calcination.The morphology and structure of the material are characterized by SEM,XRD,XPS,DRS,Mott-Schottky and other means.The photoelectrochemical properties were characterized by transient photocurrent,electrochemical impedance,photoluminescence spectrum,etc.The results show that the successful construction of Z-type heterojunction can significantly improve the separation efficiency of photogenerated electron-hole pairs of WO₃ and enhance the light absorption intensity,retain the strong redox ability of the photocatalyst.3D WO₃@Co₂SnO₄ Z-type heterojunction photoelectrocatalytic material was used as the photocathode for the production of H₂O₂.Under the optimal conditions,H₂O₂ production can reach1.34 mmol·L^-1·h^-1.The results of free radical capture and rotating disc test revealed the existence of direct one-step two-electron ORR and indirect two-step one-electron ORR to produce H₂O₂.Based on the excellent H₂O₂ production performance of3D WO₃@Co₂SnO₄Z-type heterojunction photoelectrocatalytic material,WO₃@Co₂SnO₄ and stainless steel mesh（SSM）were used to construct a dual-cathode photoelectric-Fenton system for in situ degradation of a variety of pollutants in water,such as dye methyl orange（MO）,rhodamine B（Rh B）,the antibiotic tetracycline（TC）,sulfamethazine（SMR）,ciprofloxacin（CIP）,the pesticide chlortoluron（CHI）and the heavy metal ion Cr（Ⅵ）.Using terephthalic acid as a probe,fluorescence spectrophotometry was used to detect·OH radicals in the system,and the degradation mechanism was revealed,indicating that the constructed two-cathode photoelectron-Fenton system has certain universal application to the degradation of different types of pollutions.This work provides insights into the mechanism of photoelectrocatalytic ORR production of H₂O₂,and provides ideas for designing high-activity photoelectrocatalytic materials to produce H₂O₂,and provides reference value for the construction of photoelectric-Fenton system without additional additives.（2）Constructed the coupling system of cathode and anode to explore the performance of photoelectrocatalytic bi-directional H₂O₂ production.Firstly,the anodic water oxidation production H₂O₂was studied by Fe₂O₃-Ti photoanode.The successful synthesis of Fe₂O₃semiconductor was demonstrated by SEM,XRD and Raman characterization,and the photoelectrochemical properties of the material were tested by solid ultraviolet and Mott-Schottky.The Fe₂O₃-Ti photoanode was used for water oxidation to produce H₂O₂.The potential,the type and concentration of electrolyte solution were optimized.The output of H₂O₂reached110.27μmol·L^-1·h^-1 under the best experimental conditions.This paper studies the collaborative production of H₂O₂by coupling photoanode（Fe₂O₃-Ti）and photocathode（WO₃@Co₂SnO₄）in the H-type electrolytic cell.Driven by cathode,at a voltage of-0.7 V,the production of H₂O₂ reached 919.56μmol·L^-1·h^-1.This work provides reference value and research ideas for the construction of bi-directional photoelectrocatalytic for the production of H₂O₂through the coupling of cathode and anode.