Fabrication And Perfomances Investigation Of MnO_x/CeO₂ CATHO-D E Catalyst For Lithium-AIR Battery

Nowadays, there gradually appears energy crisis due to excessive utilization non-renewable energy sources of coal and oil. At the same time, excessive consumption of these fossil fuels has caused serious environmental problems, such as greenhouse effect and hazy weather, which directly influence human health. Therefore, it is vital and urgent to develop novel renewable energy technology.As one of next generation lithium batteries, lithium air batteries combine characteristics of Li ion batteries and fuel cells, possessing many advances of high specific energy density, environment friendly and low cost, etc. which have already attracted much attentions in recent years. However, many challenges must be overcome before they can be considered further for practical applications, including high overpotential, poor rate capability, short cycle life and low electrolyte stability. Developing novel highly efficient catalyst for both oxygen reduction and evolution reactions is one of key strategies to solve these problems. The main purpose of my thesis is to study CeO2-based materials as catalyst of lithium air batteries.MnOx decorated CeO2 nanotube has been in-situ prepared through a hydrothermal process. Scanning electron microscope (SEM) and transmission electron microscope (TEM) results show that MnOx/Ce02 composite materials are hollow tube structure, MnOx nanoparticles were distributed evenly in the outer wall of CeO2 nanotube. HRTEM and XPS results display that MnOx are main MnO2 and Mn2O3。 Catalytic activites of MnOx/CeO2 composite materials for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been evaluated by the rotating ring-disk electrode (RRDE) technique. The onset potential for the ORR of MnOx/CeO2 composite materials is-0.15 V, which is right shift 40 mV compared with that of CeO2 material, and the diffusion current density of MnOx/CeO2 composite materials is 1.5 times than that of CeO2 material, suggesting that MnOx/CeO2 composite materials have better catalytic activities for the ORR. Also, MnOx/CeO2 composite materials exhibits enhanced catalytic activities for the OER.2032 lithium air batteries have been assembled with MnOx/CeO2 composite materials and CeO2 material as cathode catalyst, respectively. The first discharged specific energy density of MnOx/CeO2 catalyst based lithium air battery is 1434 mAhg-1 under 100 mAg-1 current density, while that of CeO2 catalyst based lithium air battery is only 1100 mAhg-1. Moreover, the rate capability and energy conversion efficiency of MnOx/CeO2 catalyst based lithium air battery have been greatly improved. In conclusion, MnOx/CeO2 composite materials could be a potential efficient cathode catalyst of lithium air batteries.