Preparation And Electrochemical Properties Of Ce-based Composites

The rapid development of the global economy has made energy and the environment a difficult problem to limit the sustainable development of the present human society.Due to the depletion of fossil fuels and the increase of environmental pollution,mankind urgently needs green,efficient,clean and sustainable energy to meet the needs of production and other aspects.But the development of environmentally friendly energy is inseparable from new technologies related to energy conversion and storage,such as batteries,fuel cells,water decomposition,and electrochemical supercapacitors?ES?.As one of the promising energy storage devices in future energy technologies,supercapacitors have caused more and more attention in solving emerging energy demand because of their characteristics such as high power output,long cycle life and fast charge-discharge?CHDH?.But its low energy density and high cost production limit its development,so in order to overcome these problems,electrode material research has become critical.The ability to convert between Ce³⁺and Ce⁴⁺in CeO₂ makes it a good redox material that can be applied to supercapacitors.Although CeO₂ has good redox properties,its conductivity and structural stability are poor.When Ce⁴⁺is reduced to Ce³⁺,its lattice always expands.Therefore,it cannot be used alone for electrode materials.In order to meet the requirements of high-performance supercapacitors,while having good capacitance performance,rate performance,energy density and cycle stability,CeO₂ must be compounded with carbon materials or other metal oxides.This work mainly focuses on the preparation and electrochemical performance of low-cost cerium-based micro/nanocomposites.The research process and results are divided into the following sections:?1?Preparation and electrochemical properties of CeO₂/Fe₂O₃ and CeO₂-Fe₂O₃/C compositesCe?NO₃?₃?6H₂O and 1,1'-dicarboxyferrocene acid(C₁₂H₁₀FeO₄)were used as raw materials and ethanol was used as solvent.The cerium-based coordination polymer with microspherical morphology was successfully prepared by solvothermal method,and the effect of time,temperature and reactant ratio on the morphology and structure of the precursor was investigated.The precursor of cerium-based coordination polymer was calcined at 800^oC for 4 h under different atmosphere to obtain two kinds of composite materials with different carbon contents.The hollow spherical CeO₂/Fe₂O₃ material was obtained by calcination in air atmosphere,while the solid spherical CeO₂-Fe₂O₃/C material was obtained by calcination in nitrogen atmosphere.The electrochemical performance of these two kinds of electrode materials was tested respectively in 6 M KOH electrolyte.What's more,the CeO₂-Fe₂O₃/C material was also found to have a significant adsorption effect on Acid Orange II dye.?2?Synthesis and electrochemical properties of Ce,Mo,Ni-based supercapacitor functional materialsUsing Ce?NO₃?₃·6H₂O,Na₂MoO₄·2H₂O and Ni?CH₃COOH?₂·4H₂O as raw materials and water as solvent,a series of coordination polymers with micron flower morphology were successfully prepared by hydrothermal method.The coordination polymer precursors were calcined in air atmosphere at 450^oC for 2 h to obtain several bimetallic and multimetallic oxides with similar precursor morphology:NiMoO₄,Ce₂Mo₃O₁₂,Ni/Ce₂Mo₃O₁₂-CeO₂,Ni/Ce₂Mo₃O₁₂.A series of characterization of the products were performed.Finally,the electrochemical properties of these prepared electrode materials were tested in 2 M KOH electrolyte.The test results show that the capacitance?Csp?of NiMoO₄,Ce₂Mo₃O₁₂,Ni/Ce₂Mo₃O₁₂-CeO₂,and Ni/Ce₂Mo₃O₁₂materials reach 430 F/g,213 F/g,328 F/g,722 F/g respectively,at a scan rate of 1mV/s.?3?Fe-doped CeO₂ flower-like superstructures:fast microwave synthesis and their catalytic performance for oxygen evolution reactionCe?NO₃?₃·6H₂O and K₃[Fe?C₂O₄?₃]·3H₂O were used as raw materials and water was used as the solvent,Ce-based coordination polymer with three-dimensional flower morphology was successfully prepared by microwave-assisted method.The effects of time,temperature and ratio of reactants on the morphology and structure of the precursors were investigated in detail.The coordination polymer precursors were calcined at 400,500 and 600 ^oC for 3 h in air atmosphere to obtain three Fe-doped ceria.Due to the synergy between Ce and Fe,the electrocatalyst showed excellent OER?oxygen evolution reaction?performance in 1 M KOH electrolyte.