Study On The Performance Of Photocatalytic Fuel Cell Semiconductor Polymer-WO₃ Modified TiO₂ Photoanode

In recent years,with the rapid growth of population and the rapid development of industry,a large number of organic wastes are discharged into the water body,resulting in serious water pollution,which not only seriously threatens the quality of drinking water and human health,but also wastes the rich chemical energy in wastewater.Therefore,it is necessary to develop a technology that can not only effectively degrade organic waste,but also use its chemical energy as a resource.Photocatalytic fuel cell（PFC）is considered as a candidate technology for wastewater treatment and synchronous power generation.Photoanode is not only the key component of PFC,but also the limiting factor to improve the performance of PFC.TiO₂ is widely used as photocatalyst because of its high photocatalytic activity and stability.However,TiO₂ photocatalysts can only respond to ultraviolet light（4-5%sunlight）.Although the combination of TiO₂ and WO₃ expands its photoelectric properties to a certain extent,there are still some problems such as easy recombination of electron electron-hole pairs,which inhibit the improvement of PFC performance.In this paper,a high-performance PFC photoanode was prepared by modifying WO₃/TiO₂ with semiconductor polymers（g-C₃N₄,PPy and PDA）,which promoted the separation of electron-hole pairs in the photoanode,and then improved the photoelectric properties of PFC and the degradation efficiency of Rh B.The specific research contents and conclusions are as follows:1.The g-C₃N₄/WO₃/TiO₂/Ti electrode was successfully prepared by using g-C₃N₄ and WO₃ composite sol-gel.The optimum preparation conditions were as follows:g-C₃N₄doping amount was 0.1 g,the coating number of composite catalyst was 3 layers,calcination temperature was 550℃,and calcination time was 2 h.The elemental analysis,valence structure and surface morphology of the photoanode were characterized by DRS,XRD,XPS and SEM.It was proved that the 0.1-g-C₃N₄/WO₃/TiO₂/Ti electrode was successfully prepared and had the best visible light response.0.1-G/W/Ti-PFC was constructed by combining 0.1-g-C₃N₄/WO₃/TiO₂/Ti photoanode with Cu cathode.The optimum water treatment conditions were obtained:the initial concentration of Rh B was 10 mg/L,the initial p H was 3.0,and the concentration of Na₂SO₄ was 0.1 mol/L.The short-circuit current density,open circuit voltage,maximum power density,filling factor and 2 h Rh B degradation efficiency of 0.1-G/W/Ti-PFC were 0.20 m A·cm^-2,0.598 V,19.35μW·cm^-2,0.161 and87.7%,respectively.Mechanism analysis shows the reason for the high efficiency of 0.1-G/W/Ti-PFC:WO₃/TiO₂,g-C₃N₄/TiO₂ and g-C₃N₄/WO₃ multi heterojunction structures are formed in g-C₃N₄/WO₃/TiO₂/Ti photoanode,which improves the carrier migration rate and reduces the recombination of photogenerated electrons and holes.2.The PPy/WO₃/TiO₂/Ti electrode was successfully prepared,and the optimum preparation conditions were obtained:PPy doping content was 14%,the number of coating layers was 3 layers of composite catalyst and 3 layers of TiO₂ film,calcination temperature was 150℃,and the optimum calcination time of the electrode was 2 h.The results of photoanode characterization by XRD,XPS,LSV,FT-IR,DRS and SEM showed that PPy/WO₃/TiO₂/Ti was successfully prepared.DRS test shows that PPy/WO₃ composite can effectively enhance the visible light absorption of PPy/WO₃/TiO₂/Ti electrode.PPy-14%/WO₃/TiO₂/Ti photoanode was combined with Cu cathode to construct P-14%/W/Ti-PFC.The optimum water treatment conditions were optimized:the initial concentration of Rh B was 10 mg/L,the initial p H was 3.0,and the concentration of Na₂SO₄ is 0.1 mol/L.After optimization,the short-circuit current density of P-14%/W/Ti-PFC is 0.25 m A·cm^-2and the maximum power density is 25.48μW·cm^-2,open circuit voltage is 0.508 V,filling factor is 0.201 and 2 h Rh B degradation efficiency is 88.5%.The visible light response and repeatability test of P-14%/W/Ti-PFC shows that P-14%/W/Ti-PFC has good visible light response and reusability.Free radical capture experiments showed that h⁺,·OH and·O^2-were involved in the degradation of Rh B,but h⁺and·OH played a major role in the degradation of Rh B.The mechanism analysis shows that the stepped heterojunction formed by PPy-14%/WO₃/TiO₂ composite catalyst is conducive to the rapid transfer of photogenerated holes and electrons to HOMO of PPy and CB of WO₃,so as to inhibit the recombination of photogenerated electron-hole pairs,and promote the improvement of PFC electrochemical performance and Rh B degradation efficiency.3.PDA/WO₃/TiO₂/Ti electrode was successfully prepared,and the optimum preparation conditions were optimized:the doping amount of PDA was was 11.5%,the number of coating layers was 2 layers of composite catalyst and 3 layers of TiO₂ film,the calcination temperature was 175℃,and the calcination time was 2 h.XRD,XPS,SEM and FT-IR showed that PDA/WO₃/TiO₂/Ti electrode was successfully prepared,DRS test showed that PDA-11.5%/WO₃/TiO₂/Ti expands the light absorption range of photoanode.PDA-11.5%/W/Ti-PFC was constructed by combining PDA-11.5%/WO₃/TiO₂/Ti photoanode with Cu cathode.The optimum water treatment conditions of PFC were optimized:the initial concentration of RHB is 10 mg/L,the initial p H is 3.0,and the concentration of Na₂SO₄ is 0.1 mol/L.The short-circuit current density of PDA-11.5%/W/Ti-PFC is 0.18 m A·cm^-2 and the maximum power density is 18.68μW·cm^-2,open circuit voltage is 0.520 V,filling factor is 0.190 and 2 h Rh B degradation efficiency is 84.6%.PDA-11.5%/W/Ti-PFC has good visible light response and repeatability.The mechanism analysis shows that the introduction of PDA forms a stepped heterojunction in the photoanode,which quickly transfers photogenerated holes and electrons to HOMO of PDA and CB of WO₃,respectively,which promotes the separation of photogenerated hole-electron pairs,and improves the Rh B degradation efficiency and power generation performance of PDA-11.5%/W/Ti-PFC.4.Through comparison of the main electrical properties and Rh B degradation efficiency of 0.1-G/W/Ti-PFC,PPy-14%/W/Ti-PFC and PDA-11.5%/W/Ti-PFC.it is known that PPy-14%/W/Ti-PFC has the best electrical properties and Rh B degradation efficiency.Therefore,PPy-14%/W/Ti-PFC is the best PFC system in this paper.In this paper,TiO₂ was co-modified with semiconductor polymer and WO₃ to prepare a photocatalysis with high photocatalytic activity,which was used to construct PFC to treat dye wastewater and improve its electrical properties and Rh B degradation efficiency.The semiconductor polymer modified photocathode proposed in this paper can provide a reference for the design of high-efficiency PFC photocathode.