Performance Of Vanadium-based Catalytic Materials Based On Polyoxometalate In Counter Electrodes Of Dye-sensitized Solar Cells

Dye-sensitized solar cells（DSCs）,as a representative photoelectric conversion device,can efficiently and economically convert solar energy into electric energy,which has attracted more and more attention in recent years.As an important component of DSCs,the counter electrodes（CEs）catalyzes the reduction of I₃^-to I^-in the electrolyte,and realizes the circulation of electrons in the whole circuit.Traditional counter electrode catalysts are high efficient,stable and broad-spectrum precious metal Pt.However,Pt has disadvantages such as low abundance,high cost and easy to be corroded in iodine electrolyte.Therefore,the development of cheap,efficient and stable non-Pt counter electrode materials has become one of the research hotspots of DSCs.In this paper,ammonium polyoxate polyvanadate was used as raw material to synthesize complex precursors with different organic functional compounds,and then high temperature pyrolysis was used to prepare vanadium-based catalytic materials,which were applied to the counter electrode of DSCs.Relevant research contents are as follows:1.A series of V₂O₃/VC counter electrode catalytic materials were prepared by pyrolysis of polyvanadate(（NH₄）₂V₆O₁₆)and glucose(C₆H₁₂O₆)at different temperatures（600,700,800,900 and 1000℃）,that structure characterization and electrochemical test of the prepared materials were carried out.The electrochemical test results show that the best power conversion efficiency is 6.82%when the pyrolysis temperature is 900℃.V₂O₃ counter electrode material,which using ethylene glycol as carbon source,was obtained by pyrolysis at high temperature.The results show that the photovoltaic efficiency of the counter electrode material obtained at 700℃reaches 5.57%.2.Carbon supported vanadium carbide composites were prepared by high temperature pyrolysis of precursors obtained by ball milling of polyvanadate(（NH₄）₂V₆O₁₆)and dicyandiamide（C₂H₄N₄）at five different mass ratios（6:1,12:1,18:1,24:1 and 30:1）.The influence of different pyrolysis temperatures on the preparation of electrode catalytic materials was further investigated.A series of characterization and electrochemical test results show that when the ratio of the precursor is 18:1,the catalytic material prepared by pyrolysis at 900℃has the strongest diffraction peak and the best crystal shape,the largest surface area and the highest energy conversion efficiency of 6.64%.3.The precursors of polyvanadate(（NH₄）₂V₆O₁₆)and melamine（C₃H₆N₆）were prepared by chemical mixing method,gel-sol method,solvothermal method,hydrothermal method and ball milling method,and the carbon supported vanadium nitrode composites were obtained by high temperature pyrolysis.The power conversion efficiency of the counter electrode material prepared by chemical mixing method is 5.93%.For the catalytic materials prepared by this method,the influence of different pyrolysis time on electrode materials was investigated.When the pyrolysis time increased to 5 h,the activity degree of VN@C was better,with more defect sites,and the power conversion efficiency reached 6.33%,which increased by about 6.7% compared with the previous.