Preparation Of Titanium Dioxide Nanorod Array Photoelectrode And Its Application In Photocatalytic Fuel Cells

Environmental pollution and energy crisis are two main problems faced by the development of human society,in particular,all kinds of wastewater generated in the process of industrialization and urbanization are discharged into natural water bodies,which seriously damage the balance of the ecosystem,affect people’s health and restrict the sustainable development of the economy.What’s more,the organic compounds in the waste water store a lot of chemical energy causing a waste of energy.Wastewater recycling technology is the hotspot and difficulty of water pollution control research at present,and one of the most effective methods to solve environmental problems and alleviate energy crisis.With the rapid development of semiconductor technology,photocatalytic fuel cells（PFC）based on semiconductors as photocatalytic materials is widely utilized in environmental governance and green energy development.However,there are still several key issues in the existing PFC,including the design and preparation of high-efficiency photoanodes and the optimal design of the system.In this paper,A unassisted,visible light-responsive PFC was proposed for efficiently removing organics coupled with producing electricity and hydrogen using sunlight based on photocatalysis and photovoltaic technology.The recombination rate of photegenerated electrons and holes has reduced by using titanium dioxide nanorod array（TiO₂ nanorod,TNR）photocatalytic material as the substrate for doping modification.The PFC system was successfully constructed with a photoanode which connected in series with a modified TNR and a silicon solar cell（SC）and a platinum cathode.The performance and the influencing factors of the PFC system were investigated.Specifically,the main content of this research is as follows:A unassisted hybrid tandem PFC is constructed by a monolithic photoanode,which was assembled with attaching a SC at the reverse side of a highly active antimony doped TiO₂nanorod array（Sb doped TiO₂ nanorod array,Sb/TNR）photoelectrode material for application of photocatalytic wastewater resources.The Sb/TNR was prepared in a simple hydrothermal synthesis method by using fluorine-doped tin dioxide conductive glass（FTO）as the substrate,and optimizing the synthesis conditions,the optimal doping amount was determined.Then,by using SEM,TEM,EDX-mapping,XRD,XPS,UV-vis Drs and other methods to characterize it,and test its photoelectrochemical performance.The results show that Sb/TNR grows vertically and orderly on the FTO substrate,and the photocurrent at an external voltage of 0.2 V vs Ag/AgCl is 0.77 mA cm^-2,which is～181%of the original TNR.This is mainly because the doped Sb as an electron capture center effectively improves the charge separation and increases the carrier density.The PFC showed a removal ratio of nearly100%for dichlorophenol（2-CP）and total onganic carbon（TOC）for 31.8%After 4 hours operation under AM1.5 illumination,and achieved an anverge hydrogen production rate of31.4μmol h^-1 cm^-2 and an excellent electricity output with an open circuit voltage(V_oc)of～2.16V,short circuit current(J_sc)is 1857μA cm^-2,and maximum power(P_max)is 967μW cm^-2,which is～10.8 times higher than the power density of the reported in the literature.The outstanding capability can be due to the high internal bias generated by the long-wave light captured by the SC,which promotes the rapid transfer of charge and greatly improves the utilization of the solar spectrum.The results also show that under simulated sunlight,the system has good stability in degrading different organic pollutants for power generation and hydrogen production.We further found that Sb/TNR morphology structure,light intensity,light area,initial organic concentration and pH and other factors have an important impact on system performance.In addition,we structured a novel,self-driven,hybrid tandem PFC through SC attached to the back of the Si/TNR photoelectrode material for efficient solar hydrogen production coupled with organic degradation.The Si/TNR with vertically arranged nanorods is prepared by a facile hydrothermal method and has improved charge transport properties and donor density due to the homogenously distributed silicon in the TiO₂ matrix The photoelectrochemical performance test showed that the Si/TNR has enhanced photocurrent density that is high as～0.76 mA cm^-2 at 0.2 V vs Ag/AgCl,which is about～271%of the photocurrent density of the undoped sample.By combining the excellent characteristics of Si/TNR and SC,PFC shows a superior performance for tetracycline hydrochloride（TC）degradation and hydrogen production,with a removal ratio of 94.3%after 1.5 h of operation and average hydrogen generation rate of～28.8μmol h^-1 cm^-2.Compared to conventional PFC,PFC has improved light absorption and charge transfer capabilities,which is due to the synergistic effect between Si/TNR and SC.The results also indicate that the PFC has highly flexibility,adaptability and stability in the treatment of wastewater containing various organic substances,and a wide range of pH values and salinities.In conclusion,the photoelectrode material was modified by metal ion doping,which effectively improves the photoelectric conversion efficiency while suppressing the recombination of photogenerated carriers.The metal ions introduced in the Ti O₂ matrix serve as the trapping sites for photogenerated electrons,which promotes the separation of charges and is beneficial to the generation of oxygen vacancies.With the reasonable coupling of photovoltaic technology and the synergistic effect of photoelectrode with SC,the PFC system constructed with composite photoanode structure has better performance than traditional pfc,and realizes the maximum utilization of solar energy,spontaneously degrade organic under the visible light illumination to recover electrical energy while generating clean energy-hydrogen.This idea is of great significance to the development of efficient and stable PFC system for environmental governance and the development of green energy.