Preparation And Properties Of Ceria-Based Oxygen Reduction Catalysts

As people pay more and more attention to the environment,fuel cells have received more and more attention due to their non-polluting and high energy conversion efficiency.The oxygen reduction catalysts currently used in fuel cells are Pt catalysts.Although platinum catalysts have high activity,their high cost and poor stability make them unsuitable for commercial large-scale promotion.Therefore,the development of non-noble metal oxygen reduction catalysts with high activity,low cost and excellent stability is very important for the commercial application of propulsion fuel cells.In this thesis,the research of ceria is based on the doping of non-precious metals and carbon materials to control the structure and composition of ceria.The details are as follows:（1）Nano-cerium oxide and cerium oxide-doped cobalt materials in hollow spherical shape were successfully synthesized by spray pyrolysis.The addition of Co helps to increase the number of ORR active sites in ceria,thereby improving the ORR activity of cobalt-doped ceria catalysts.The initial potential is 0.68 V and the half-wave potential is 0.587 V,which are higher than those of cerium oxide,and the cerium oxide doped with cobalt tends to the four-electron transfer pathway,while the redox reaction of pure cerium oxide proceeds according to the two-electron reaction.（2）The cerium oxide-doped cobalt prepared by the hydrothermal method has excellent porosity and large specific surface area,which enables better utilization of the active sites of the catalyst and provides a basis for an efficient mass transfer process.The half-wave potential of cobalt-doped ceria reaches 0.623 V,and the electron transfer number is 3.82,which is close to the four-electron reaction process,indicating that the hydrothermally prepared cobalt-doped ceria has better performance than ceria because of its large surface area.,more oxygen vacancies and a unique mesoporous hollow spherical structure.（3）The C-CeO₂catalyst was successfully prepared by the hydrothermal method.After a series of characterization tests,the analysis showed that the carbonized material after hydrothermal treatment has a higher specific surface area and a richer pore structure.The initial potential of C-CeO₂catalyst is 0.82 V and the half-wave potential is 0.784 V,which are higher than those of hydrothermal ceria catalyst,indicating that the prepared C-CeO₂catalyst has great development potential.Not only that,it can be seen from the K-L diagram that the electron transfer number of the C-CeO₂catalyst is close to 4,indicating that the process is a four-electron reaction.It shows that carbon materials and cerium oxide form a mixed carrier,which can overcome the disadvantage of poor electrical conductivity of cerium oxide,and the rich pore structure of carbon materials improves the electrochemical performance of cerium oxide.