Preparation And Performance Of Graphene Supported Nanomaterials As Counter Electrodes For Dye-sensitized Solar Cells

As one of the third-generation solar cells,dye-sensitized solar cells(DSSCs)have been the focus in the photovoltaic field.Counter electrode(CE)is one of main components in DSSCs,which functions collecting and transferring electrons and accelerating the reduction of I3-.At present,platinum(Pt)metal is the primary catalytic material for CEs,but its properties including limited resources,high cost and instability decelerate the commercialization of DSSCs.As such,developing cheap,efficient and stable catalysts is an effective measure to overcome this key problem.Carbon materials represented by graphene,with low cost,high conductivity and good stability,are expected to replace the noble Pt.This thesis aims to improve the catalytic activity of graphene materials.The cobalt phosphide/graphene composite(CoP/rGO)and antimony nanoparticles/graphene nanoribbons composite(Sb/GNR)were respectively constructed and applied to the catalytic materials of counter electrode for DSSCs.And their catalytic behaviors of I3-reduction reaction were investigated.CoP/rGO composites were prepared by one-step phosphating with cobalt-based Prussian blue analogues(Co PBA)and graphene oxide(GO)hybrid as a precursor and NaH2PO2 as phosphorus source.In this process,Co PBA in-situ translated into CoP with the three-dimensional cube morphology,whose porous frame structure provides favorable channels for the diffusion of I3-.The electrochemical performance of CoP/rGO was optimized by adjusting the amount of graphite oxide(50 mg,100 mg,150 mg,200 mg).It was found that CoP/rGO-100 showed the greatest electrochemical performance.The DSSC with the CoP/rGO-100 CE delivered a power conversion efficiency(PCE)of 7.17%,which was close to Pt CE(7.30%),and higher than CoP(4.78%)and rGO(6.31%)CEs.One-dimensional graphene oxide nanoribbons(GONR)with rich edges were prepared by chemical unzipping carbon nanotubes.Then antimony nanoparticle/graphene nanoribbons(Sb/GNR)composites were synthesized by high-temperature annealing with GONR as the substrate and SbCl3 as the antimony source.It was found that,compared with the carbon substrates of antimony/graphene(Sb/rGO)and antimony/carbon nanotubes(Sb/CNT)composites,the one-dimensional structure of GNR substrate enhanced the carrier transport rate,while its abundant edges increased the catalytic active sites.Therefore,Sb/GNR showed excellent electrocatalytic activity towards I3reduction.In addition,Sb nanoparticles were tightly anchored to the surface of GNR through interaction of Sb-O-C bond,which not only activated the inert surface of GNR,but also enhanced electrochemical stability of Sb/GNR composites.The DSSC with the CoP/rGO-100 CE achieved a high PCE of 8.47%,superior to Sb/rGO(7.31%),Sb/CNT(7.54%)and Pt(8.27%)CEs.