| Dye-sensitized solar cells（DSCs）is an ideal photoelectric conversion device,which has been the research hotspot of the photovoltaic field in recent years.The DSCs is consisted of three parts,the photoanode,the counter electrode and the electrolyte.The electrode is an important part of the DSCs system,which is responsible for catalyzing the redox couple in the regenerated electrolyte.Precious metal-platinum（Pt）has a good catalytic activity that can be the ideal electrode material for DSCs.However,the Pt is expensive and the reserves of Pt are limited,all that limit its wide application in DSCs.Therefore,in order to overcome these shortcomings,it is urgent to develop a cheap efficient counter electrode catalytic material.Carbon materials,with low cost,high conductivity,rich source of raw materials and other characteristics,can be used as a catalyst for electrode,widely used in DSCs.There are several carbon materials,such as activated carbon,carbon black,ordered mesoporous carbon,graphene,CNTs,fullerenes and so on.In order to develop a new and efficient low-cost DSCs electrode catalytic material,this paper mainly undertakes from two aspects: on the one hand,a new type of electrode material nano-carbon sphere（CS）is designed and synthesized to replace Pt as the electrode of DSCs;on the other hand,it is possible to reduce the amount of Pt by using the composite counter electrode which is synthesized as the carbon sphere with Pt（Pt / CS）,instead of the Pt electrode.In this paper,a monodispersed solid carbon sphere（SCS）is synthesized by the hydrothermal method.The size of the carbon sphere is 420 nm and the specific surface area is 380.97 m2g-1.Based on this carbon sphere,the energy conversion efficiency of DSCs is 8.60%,but still lower than that of DSCs with Pt as the electrode.The energy conversion efficiency is 9.41%.In order to improve the catalytic performance of carbon sphere,we further synthesize the carbon spheres that with particle sizes of 250,320 and 550 nm.It is found that the carbon nanotubes with particle size of 250 nm have the highest catalytic activity because of the larger specific surface area（454.47 m2g-1）,so it can provide more catalytic activity sites,corresponding to the efficiency of DSCs reaches 9.32%.It canbe seen that the catalytic performance of carbon sphere with a diameter of 250 nm is very close to that of Pt.In addition,in order to improve the catalytic performance of CS,Pt / CS composite electrode is prepared,and the effect of Pt-loading on its catalytic activity is characterized.The experimental results show that the catalytic activity of Pt / CS is the highest when the loading of Pt is 2.1 wt %,and the efficiency of DSCs based on this electrode is 9.05%,which is higher than that of Pt（8.42%）,and higher than the efficiency（6.70%）of DSCs with CS as the electrode.In order to verify the high catalytic performance of Pt / CS,the activation energy of Co3+/2+ on Pt / CS electrode is 26.55 kJ mol-1 by electrochemical impedance experiment,which is lower than that of Pt/CS（37.03 kJ mol-1）,the reason for the high catalytic activity of Pt / CS is fundamentally explained.Therefore,this method of loading Pt nanoparticles onto CS surface can reduce the amount of Pt and improve the catalytic activity of the electrode material.In this paper,two kinds of electrode materials —— carbon sphere and Pt / CS,have been successfully synthesized,which can effectively reduce the production cost of DSCs and improve the energy conversion efficiency of DSCs. |
