Controllable Preparation And Property Study Of The Cobalt-iron Based Carbon Composites

With the rapid development of society,energy crisis and environmental pollution have been the two main problems that challenge to human being.This has led us to evaluate a new environment-friendly alternative energy sources.Solar and hydrogen energy are sustainable,abundant,clean,and thus attracted much attentions as the alternatives to fossil fuels.Solar cells and（photo）electrochemical water splitting are two important ways to realize the utilization of solar and hydrogen energy.However,their high fabrication cost and low efficiency limited their practical applications at present.To solve the problem,we prepared a series of cobalt-iron composite carbon materials from the low-cost and readily available sulfonated asphalt,which can be used as the catalytic materials in solar cell as well as water splitting system.The main work is as follows:（1）The metal/carbon composites were prepared by using the cobalt and iron chlorides as metal sources and sulfonated asphalt as carbon source.Their structure of the composites were controlled by controlling the reaction conditions such as carbonization temperature,reactant composition etc.The structure of the composites were characterize by XRD,SEM,BET analyses etc.The results show that both the carbonization temperature and the reactant composition are important factors in determining the structure of resulted metal/carbon composites:low carbonization temperature is favorable for the formation of CoFe₂O₄,high carbonization temperature is apt to forming CoFealloys,whereas the presence of bimetals or the higher metal content is beneficial to the formation of sheet-like structures.（2）The metal/carbon composites were used to fabricate the CdSe QDSSCs.Cells performance investigations show that the bimetallic carbon composite（C@CoFe/CoFeO_x）carbonized at 700℃hold the best cell performance with the photoelectric conversion efficiency reached to 5.08%.To improve the cell performance,C@CoFe/CoFeO_x was further post-treated by methylhexylimidazolium iodide.Cell performance investigation shows that the treatment greatly increased the cell performance of CdSe QDSSCs,and the cell efficiency of 6.37%was achieved,which is much higher than that of the PbS based device（5.40%）.In view of the surface and kinetics analyses,two redox couples working mechanism related to the imidazole iodine is proposed.（3）The metal/carbon composites were used as the electrocatalyst for oxygen evolution reaction,and their catalytic properties were investigated.Results show that,the sheet structured C@CoFe composite,prepared with sulfonated asphalt/metal chlorides（2:1 in weight）and carbonized at 750℃,exhibits the best OER catalytic activity with an overpotential of 304 mV at 10 mA/cm² in 1 M KOH,which is comparable to that of normally used IrO₂ catalyst（275 mV）.