Application Of Fe-Co Compounds In The Counter Electrode Of Dye-sensitized Solar Cells

Since the first fires were made hundreds of thousands of years ago,energy has been an important cornerstone of social progress and development.Our life is inseparable from the application of energy.Fossil fuel is the main energy source at the present stage.With the development of industry,at this stage,the problems caused by energy have gradually emerged.In order to prevent the deterioration of the energy crisis and pollution,it is very necessary for human society to develop new energy sources.At the same time,the newly developed energy must be environmentally friendly and renewable There are many branches of new energy devices.Nowadays,the hot research direction includes fuel cell,lithium battery,supercapacitor,zinc-air battery,solar cell,and so on.Among them,solar cells occupy an important position.There are also many research directions for solar cells.Dye-sensitized solar cells（DSSCs）have the advantages of abundant raw materials,less pollution,simple structure,and easy assembly.At the same time,it also has a high solar energy conversion efficiency,which makes it become one of the hot research directions at present.The counter electrode（CSs）of DSSCs plays an important part of the work in the whole-cell device.In the past research,Platinum（Pt）has been considered as an ideal CEs material due to its excellent electrical conductivity and catalytic efficiency.However,as a precious metal,platinum is very expensive,so it is difficult to use platinum as a counterelectrode in mass production.If it cannot be put into industrial mass production,the research on dye-sensitized solar cells can only stop in the laboratory.Therefore,the research content described in this paper is to develop a more easily produced counter electrode material to replace the precious metal platinum.The research on the electrode materials of dye-sensitized solar cells is divided into many directions,among which ternary metal compounds have excellent performance in terms of electrical conductivity and catalytic efficiency.Therefore,based on iron and cobalt compounds,this paper optimized the performance improvement,manufacturing process,and other aspects,and carried out characterization and performance test for the improved materials.This paper mainly includes the following four chapters:The first chapter describes the energy problems and environmental problems faced by human beings at the present stage,which leads to people’s research on new energy materials,and introduces the origin and development process of dye-sensitized solar cells.The structure and working principle of the dye-sensitized solar cells are introduced.This paper introduces the current research on dye-sensitized solar cells for motor materials and introduces the research content of this paper.In the second chapter,the experiment is briefly introducedIn the third chapter,the CoFe₂O₄ ball string structure was prepared by hydrothermal method and then compounded with graphene.By testing and comparing the electrochemical properties of a single substance,composite structure,and platinum,the feasibility of Fe-Co compound as counter electrode was explored.In the fourth chapter,Fe-Co precursor nanoparticles were synthesized by the one-step hydrothermal method,and then CoFe₂O₄nanoparticles were synthesized by heating.In order to improve the properties of Fe-Co compounds,FeS₂/FeCoS₂nanoparticles were synthesized from Fe-Co precursors by the hydrothermal method.At the same time,REDOX graphene and FeS₂/FeCoS₂nanoparticles were synthesized to form a composite structure.The above three materials for characterization and performance tests;In the fifth chapter,Fe-Co precursors were directly grown in situ on the conductive surface of the substrate by the one-step hydrothermal method,and then FeS₂/FeCoS₂pair electrode was synthesized by hydrothermal method.The morphology of three pairs of electrode samples synthesized in different synthesis processes was compared and then compared with Pt electrode through characterization and performance test.Specific research contents and results are as follows:（1）CoFe₂O₄ spherical string structure was successfully synthesized and combined with redox graphene to form a composite structure.The electrochemical performance and photoelectric conversion performance of CoFe₂O₄,RGO and CoFe₂O₄@RGO were compared in detail.The results show that the photoelectric conversion efficiency of the composite structure reaches 6.73%.It is more than CoFe₂O₄（1.724%）and RGO（5.167%）,and close to Pt electrode（7.283%）,indicating that under the synergistic action of CoFe₂O₄catalytic performance and RGO conductive performance,a new electrode material can be prepared which can replace Pt electrode.（2）CoFe₂O₄ nanoparticles and FeS₂/FeCoS₂nanoparticles were successfully synthesized.On this basis,FeS₂/FeCoS₂nanoparticles were attached to rGO to synthesize FeS₂/FeCoS₂nanoparticles and rGO nanocomposites（FeS₂/FeCoS₂@RGO）.The electrochemical properties and photoelectric conversion properties of the three materials were compared in detail.The results show that the electrochemical and photoelectric conversion properties of FeS₂/FeCoS₂（7.05%）are significantly higher than those of CoFe₂O₄（3.71%）.It was proved that the catalytic and electrical properties of CoFe2O4 were successfully improved by curing.The proper introduction of RGO can further improve the conductivity and specific surface area of FeS₂/FeCoS₂,increase the active sites,and finally make the photoelectric conversion performance（7.84%）of FeS₂/FeCoS₂electrode exceed that of standard Pt electrode.Therefore,FeS₂/FeCoS₂@RGO meets our expectations and can replace the rare Pt electrode in DSSC devices.（3）The Fe₃S₄/Co₃S₄ material was directly grown on the surface of the FTO conductive glass by hydrothermal method,without the need of centrifugal drying,film scraping,annealing and other steps of the pair of electrode materials.According to the different experimental drugs and the different hydrothermal synthesis methods,three different structures of nanosheets,nanowires and nanowire-needle ball were prepared.The electrical properties and photoelectric conversion properties of the three structures are compared in detail.The results show that the electrochemical performance and photoelectric conversion performance（8.16%）of nanowires are much higher than those of nanowires（6.45%）and nanowires（6.39%）,and higher than that of standard Pt electrode（7.61%）.This indicates that it is possible to synthesize a kind of counter electrode material with good performance,low cost and mass production to replace Pt.