Design,synthesis And Application Of Carbon/Fe₃O₄ Composites In DSSC

Energy is a significant basis for economic development and enhancement of human living standards.Because of the non-renewability of fossil fuels and the emission of carbon dioxide greenhouse gases,this has initiated incredible damage to environment and human health.Therefore,changing the existing energy structure and developing sustainable clean energy have become the main concerns of all countries in the world.At present,solar energy is the most abundant,renewable and clean energy.It has been extensively used in energy conversion and has received numerous research reports.With the unremitting progress of solar cells,dye-sensitized solar cells(DSSCs)were improved by Gratzel and his colleagues in 1991.With the benefits of simple preparation process and excellent performance,many researchers pay attention to them.Considering that photoelectrons are produced by photosensitive dyes alone,and semiconductor is used to transport electrons under sunlight in DSSC,which is different from traditional solar cells.In DSSCs,lower recombination rate of electron holes can be achieved,so higher efficiency can be achieved.At the same time,DSSCs be made into different characters,colors and transparency to meet the different requirements of different applications.In addition,DSSCs can also generate electricity efficiently under low sunshine,which increases the indoor application.Electrodes are one of the components of dye-sensitized solar cells,while platinum is the traditional material for electrodes.It has excellent electrocatalytic performance and is recognized as a reference electrode in the field of CE catalysis.However,due to the scarcity of resource reserves,Pt is very expensive.As counter electrode materials,the high price,unstable performance,which result in cannot be used for large-scale invention and application in DSSCs.Therefore,it is of great significance for the development of dye-sensitized solar cells to find low-cost and high-performance counter electrode materials to replace the traditional platinum electrodes.So as to improve the electrochemical possessions of electrode materials in DSSCs,the design of nanostructured composites should pay attention to the following aspects:(1)Homogeneous nanostructures are helpful to the good diffusion of electronic units;(2)hollow composite nanostructures of electrode materials have outstanding electrocatalytic activity;(3)layered porous materials with high specific surface area can absorb electrons in electrolyte to the maximum extent;(4)nanocomposites should have Superstability in electrolyte;(5)simple and low-cost synthesis strategy is beneficial in practice.In view of key issues,we constructed a reasonable design and precise control to achieve highly uniform Fe3O4 nanoparticles and used dye-sensitized solar cells as electrodes in combination with carbon materials.The relevant contents are as follows:(1)a large number of uniform Fe3O4 microspheres were synthesized by simple hydrothermal method.The microspheres were aggregated,due to smaller nanoparticles.Fe3O4 microspheres were combined with amorphous carbon and graphene to form nanocomposites of metal oxides and carbon materials respectively,and were used as counter electrodes in dye-sensitized solar cells.It was found that Fe3O4 exhibited excellent catalytic performance in electrolyte,and its performance was close to that of platinum electrode.However,the steadiness of electrocatalysis is poor,which affects the large-scale application.Therefore,we first compounded the amorphous carbon with Fe3O4 microspheres.The experimental show that the steadiness of photoelectric conversion of the composite is enhanced,but the electrochemical performance of the composite is slightly lower than that of pure Fe3O4 microspheres.We suspect that the electrochemical performance of amorphous carbon may be poor,thus affecting the electrocatalytic performance of the composite.Therefore,we use graphene with better conductivity to compound;Fe3O4 spheres are encapsulated by graphene,which greatly improves the stability and electrocatalytic performance.(2)Fe3O4 nanoparticles are easy to conglomeration,which affects the contact between electrolyte and nanoparticles,leading to the failure of electrocatalytic performance.Therefore,we first design hollow core-shell mesoporous carbon microspheres and then insert Fe3O4 nanoparticles into the mesoporous of carbon microspheres.SEM and TEM show that Fe3O4 nanoparticles uniformly adhere to HCCMS,forcing Fe3O4 nanoparticles to adhere to the mesoporous.The uniform delivery of Fe3O4 on HCCMS avoids the disadvantage of agglomeration.Compared with pure Fe3O4 and core-shell carbon mesoporous microspheres,the properties of the compounds are greatly enhanced,however,the steadiness is still lowly.On this basis,we introduce graphene to form a ternary sandwich structure,and use the flexibility of graphene to package the whole,so as to resist the corrosion of electrolyte to Fe3O4 nanoparticles.Ternary composites have made great breakthroughs in photoelectric conversion and stability.(3)In DSSCs,the effect of morphology on the performance of Fe3O4 electrodes was investigated by synthesizing and designing the microstructures of Fe3O4.The electrochemical properties of two-dimensional porous Fe3O4 nanosheets and three-dimensional porous Fe3O4 nanospheres were tested under the same conditions.The results showed that three-dimensional porous Fe3O4 nanospheres exhibited electrochemical properties beyond platinum,indicating that the morphology of the nanospheres was light-sensitive.The output of electrical efficiency has a excessive effect.(4)The three-dimensional porous Fe3O4 nanoflowers were compounded with RGO and N-RGO respectively and applied to dye-sensitized solar cell pair electrodes.Three-dimensional porous Fe3O4 nanoflowers were prepared by hydrothermal method and successfully compounded with RGO and N-RGO.We found that compared with pure Fe3O4 nanoflowers and Fe3O4UFM@RGO,Fe3O4UFM@N-RGO has larger specific surface area and more reaction sites.It is clear that the performance of Fe3O4UFM@N-RGO exceeds that of pure Fe3O4 nanoflowers,Fe3O4UFM@RGO and precious metal platinum in polarization,impedance,cyclic voltammetry and PCE tests.It can be substituted for precious metal platinum as a pair of electrode materials for DSSC.