Application Of Tungsten-based Catalytic Materials Based On Polyacids In Counter Electrodes Of Dye-sensitized Solar Cells

Dye-Sensitized Solar Cells（DSCs）,as a photovoltaic device that can directly convert solar energy into electrical energy,have attracted widespread attention due to their environmental protection,high efficiency,and strong plasicity.The counter electrode is one of the important components of the DSCs,and the catalytic activity of its material directly affects the photovoltaic performance of DSCs.The traditional Pt catalyst for counter electrode has been widely used due to their high conductivity and high catalytic properties.However,Pt has the disadvantages of being expensive and easy to be corroded in by I^-/I₃^-in electrolyte.Therefore,the development of new Pt substitute materials has become a research hotspot in today’s DSCs.Tungsten-based compounds,as Pt-like semiconductor materials,have become the preferred alternative materials for electrode due to their high electron energy density,good catalytic performance and simple preparation.In this paper,polyacid phosphotungstic acid was used as the tungsten source,organic amine or metal organic framework compound（MOF）was used as the carbon source to construct the organic complex precursor,and then high temperature pyrolysis was used to prepare tungsten carbide,tungsten oxide and corresponding compound,which were applied to the counter electrode of DSCs as the catalytic material.The specific research content are as follows:1.The polyacid H₃PW₁₂O₄₀·XH₂O and dicyandiamide（C₂H₄N₄）were mixed to prepare the precursor according to 5 different mass ratios of 1:3、1:5、1:7、1:9 and 1:11,and the P-W₂C@CN electrode materials were prepared by high temperature pyrolysis.The material was characterized by XRD,SEM,XPS and the corresponding electrochemical test.The corresponding J-V results showed that the optimal efficiency was 5.32%for P-W₂C@CN with the mass ratio of 1:9.Then chemical,ball milling,and physical methods were used to prepare composite electrode materials for P-W₂C@CN-4 and carbon nanotubes（CNTs）.The photoelectric efficiency was increased to 5.95%,and the optimization rate reached 11%.2.The polyacid H₃PW₁₂O₄₀·XH₂O was assembled into the metal organic framework compound ZIF-8 by milling,and the electrode materials were calcined at high-temperature at 600℃,700℃,800℃,900℃respectively.The XRD of W₂C material prepared at 900℃showed that the diffraction peak was the strongest,indicating that the crystal shape was the best.At the same time,the electrochemical performance test showed that this material could obtain the highest photoelectric efficiency of 4.33%.Furthermore,it was compounded with graphene with different mass ratios to.Because the doping of graphene could reduce the transfer resistance and enhanced the electrical conductivity,the photoelectric efficiency was 5.12%after the composite.3.The polyacid H₃PW₁₂O₄₀·XH₂O was mixed with triethylamine hydrochloride,tetrapropyl ammonium bromide and tetrabutyl ammonium bromide respectively by solvent method,and the carbon supported tungsten oxide（WO₃@C）electrode material was prepared by pyrolysis.After a series of characterization,it was found that the electrode material prepared with tetrabutylammonium bromide had a better efficiency of 3.98%.Then the reaction conditions were optimized to determine the influence of different calcination time on the electrode materials.When the calcination time was 5h,the activation degree of WO₃@C was better,the defect sites were more,and the photovoltaic efficiency was 4.50%.