Synthesis Of Non-platinum Catalytic Materials And Their Application To Dye-sensitized Solar Cells

As the energy crisis is increasingly getting serious,it is both necessary and meaningful to exploit solar energy resources.Dye-sensitized solar cells?DSSCs?have been widely focused by researchers around the world since 1991 due to their rich raw materials,low cost,easy assembly,and strong plasticity.Typical DSSCs consist of photoanodes?dye-sensitized nanocrystalline semiconductor films?,electrolytes?I₃^-and I^-redox pairs?,and counter electrodes?generally noble metal Pt?.Pt counter electrodes are used to catalyze the redox reaction of ions in the electrolyte and collect the electrons of the external circuit.To date,the photoelectric conversion efficiency?PCE?of the DSSCs using Pt-deposited fluorine-doped tin oxide?FTO?conductive glass as the counter electrodes?CE?has reached 13%,which is the highest value in this field.However,Pt is expensive and scarce,which limits its large-scale application on DSSCs in the future.Therefore,for the purpose of replacing Pt,this work synthesized a series of composite materials using cheap and readily available compounds and applied them to the counter electrodes of dye-sensitized solar cells,and obtained relatively high photoelectric conversion efficiency.?1?To this work,a composite ZnS-PbS-CNs?ZnS-PbS imbedded in carbon nanofibers support?is synthesized with a facile one-step hydrothermal method and then introduced the composite into dye-sensitized solar cells?DSSCs?as a counter electrode?CE?catalyst.Based on the analysis of the cyclic voltammetry,electrochemical impedance spectroscopy,and Tafel-polarization curve measurements,the catalytic activity of the ZnS-PbS/CNs composite for the regeneration of iodide is indeed enhanced significantly as compared with ZnS-PbS,because the composite electrode eliminates the particle aggregation and forms a mesoporous network structure withlarge pore size.The I₃^-/I^-electrolyte based DSSCs with ZnS-PbS/CNs CE yields a high power conversion efficiency?PCE?of 7.44%,generating a great improvement as compared to the Pt CE based DSSCs.?2?In this work,a counter electrode?CE?made from a composite of electrospun carbon nanofibers?CNs?andMo O₂ nanoparticles has been discussed for the first time as an efficient and low-cost Pt-free counterelectrode?CE?for dye-sensitized solar cells?DSSCs?.MoO₂/carbon nanofiber composites?MoO₂/CNs?were successfully prepared via a facile one-step hydrothermal method.The obtained MoO₂/carbonelectrode showed good chemical stability,lower charge transfer resistance and higher electrocatalyticactivity as compared to the conventional Pt electrodes.The characteristics of DSSCs based on MoO₂/CNselectrodes were analyzed using photocurrent density-voltage,cyclic voltammetry,Tafel polarizationcurve and electrochemical impedance spectroscopy measurements.The experimental results revealedthat the MoO₂/CNs electrodes exhibited the optimal electrode characteristics.The DSSCs based on MoO₂/CNs electrodes displayed better photovoltaic conversion efficiency?7.6%?than the Pt counter electrodes?7.34%?.?3?Mesoporous carbon?MC?-imbedded tungsten carbide?W₂C?composites are synthesized via a simplemethodology and subsequently used as flexible counter electrodes?CE?in dye-sensitized solar cells?DSSCs?.The W₂C/MC composite possesses remarkable electrochemical properties for both novel organicdisulfide/thiolate and conventional triiodide/iodide redox couples,with a performance that surpasses thoseof W₂C and MC separate components.Thus,the iodide electrolyte based-DSSCs involving W₂C/MC as aflexible CE shows a power conversion efficiency?PCE?as high as 7.61%.Remarkably,the W₂C/MCcomposite is also found to be suitable as a CE for organic sulfide redox couple electrolyte based-DSSCs,showing a much higher PCE?5.96%?as compared to their separate W₂C and MC component counterparts?5.08 and 4.38%,respectively?.