Study On Preparation Of Rare Earth-based Doped Oxide Composites Catalytic Materials Of From Bayan Obo Rare Earth Tailings

Inner Mongolia Bayan Obo is rich in rare earth resources.With the rapid exploitation of rare earth resources,the increasing amounts of tailings are piled up,which contains a large number of valuable minerals,such as bastanesite,monazite,magnetite,and fluorite.This generates a great waste of resources and causes significant environmental problems.Thus,it is urgent for us to find a reasonable,feasible,green and efficient way of comprehensive utilization of rare earth tailings Meanwhile,with the gradual depletion of petrochemical energies and the ever-increasing global environmental problems,clear energy sources of all kinds of full cells with low pollution and high efficiency using cheap non-noble metal oxides as electrocatalysts are highly desired.As rich with trace elements such as Ce,Fe,Ti,Mn,Co,Ni and Nb etc.,rare earth tailings contain the main active components of non-noble metal oxide electrocatalysts.The iron-cerium mixed oxide catalyst is one of the most effective catalysts for oxygen reduction reaction of fuel cells.Their conductivity,strength and stability can be greatly enhanced by adding other metallic elements.In order to realize the high value of rare earth tailings in Bayan Obo,the rare earth-based doped oxide composites catalytic materials are prepared directly without involving in the deep separation and their composition,solution chemistry characteristic,and precipitation behaviors are studied.Based on such investigations,rare earth-based doped oxide composites catalytic materials with controllable sizes and well-defined morphologies are synthesized by adjusting the pH value of rare earth tailings solution.Meanwhile,trace elements(Al,Mg,Co,K)as dopants successfully enter the lattice of rare earth-based nanocatalysts.The catalytic performance of rare earth-based doped oxide composites catalytic materials for electrocatalysis of oxygen reduction reaction is systematically evaluated in order to explore the feasibility of their application in practical full cells.The methodology of utilizing rare earth tailings may provide independent intellectual property rights for realizing high value utilization of rare earth tailings.The first chapter is the introduction.In this chapter,we introduced the current status of comprehensive utilization of rare earth tailings and the development of cathode oxygen reduction electrocatalysts for fuel cells,thus,to establish the research topics basis and raise a new way for comprehensive utilization of rare earth tailings.In the second chapter,we studied the physicochemical properties of phase and chemical composition,solution chemistry,dissolution and precipitation etc.by means of XRD and XRF etc.Then,the rare earth hydroxide precursors for preparing rare earth-based doped oxide composites catalytic materials were achieved through the treatments of ball milling,acid leaching,and precipitation etc.In the third chapter,rare earth-based doped oxide composites catalytic materials were synthesized via a hydrothermal/solvothermal method using rare earth hydroxides obtained from the rare earth tailings as precursors.By modulating the pH value of precursor solution,surfactants,reaction temperature and time,rare earth-based doped oxide composites catalytic materials with controllable sizes and well-defined morphologies were obtained,which were characterized by XRD,SEM,and TEM.Finally,the catalytic performance of rare earth-based doped oxide composites catalytic materials for the oxygen reduction reaction in cathode of full cells was evaluated.The optimum rare earth-based doped oxide composites catalytic materials showed the relatively good catalytic activity with a half-wave potential value of 0.78 V.Our research provided a new methodology for convenient,cheap,high value-added,and comprehensive utilization of rare earth tailings.The fourth chapter is the summary of the thesis.The unfinished works due to the research time limitation as well as the prospect were given for guiding the following researchers.