Research On The Reaction Activity With Hydrogen Of Doped CeO₂ And BaCeO₃ Based Composite Oxides

Today,with the worsening environment,people are in urgent need of renewable clean energy.Hydrogen has high energy density,high calorific value of combustion,and hydrogen can combine with many elements to form compounds.It is a good carrier of clean energy,but the instability of hydrogen energy output and storage limits its application.Therefore,in order to realize the rational utilization of hydrogen energy,the development of efficient and safe hydrogen storage technology is the key.Oxide hydrogen storage materials have the characteristics of stable chemical properties,simple preparation,corrosion resistance and so on.Especially at high temperature,they can show excellent electrochemical performance,which is the current research hotspot of hydrogen storage materials.However,oxide hydrogen storage materials still have some shortcomings,such as low electrochemical capacity and low kinetic performance,which need to be improved.It is found that ion doping can effectively modify the microstructure of the oxide and improve its hydrogen storage performance.Therefore,CeO₂and BaCeO₃are selected as the research subjects in this paper to study the effects of different doping ions and doping concentrations on the microstructure of solid solutions,and then to explore the effects of doping on the hydrogen storage properties of oxide materials.Nanosized Ce_1-4x（FeAlCoLa）_xO₂（x=0.00-0.05）solid solutions were prepared by hydrothermal method.The microstructure,spectral characteristics and hydrogen reaction activity of the solid solutions were analyzed.The results show that the solid solution limit of four ions in CeO₂is x=0.03.With the increase of doping concentration,the crystallinity and Ultraviolet energy gap of the samples decreased,and the oxygen vacancy concentration of the solid solution could be increased by doping ions.Compared with pure CeO₂,the reaction temperature of doped samples with hydrogen is lower,and the reaction amount with hydrogen is significantly increased,indicating that doped ions enhance the reaction activity of CeO₂solid solution with hydrogen.Ba_0.98M_0.02CeO₃（M=Li、Sr、Na、Ca）solid solutions were prepared by combustion method.The microstructure and electrochemical hydrogen storage properties of the solid solution were analyzed.The results show that Ca²⁺,Li⁺,Na⁺and Sr³⁺successfully enter the BaCeO₃lattice to form solid solutions with good crystallinity.The electrochemical capacity retention rates of pure BaCeO₃and doped Ca²⁺,Li⁺,Na⁺and Sr³⁺solid solutions after 60 cycles at 60℃were 22.8%,70.1%,39.46%,49.4%and 40.8%respectively.The hydrogen diffusion coefficients of doped Ca²⁺and Na⁺samples are higher than that of pure BaCeO₃.Through comprehensive comparison,it is found that the samples doped with Li⁺show better electrochemical performance.In order to explore the effect of Li⁺doping concentration on the electrochemical hydrogen storage performance of BaCeO₃solid solution,Ba_1-xLi_xCeO₃（x=0.00、0.02、0.04、0.06、0.08、0.10）solid solution was prepared by combustion method.Electrochemical tests showed that the maximum specific discharge capacities of the samples were 217 mAh/g,185 mAh/g,116 mAh/g,135 mAh/g,233mAh/g and 242 mAh/g respectively.With the increase of doping concentration,the maximum specific discharge capacity and cycle stability of the samples also increased.BaCe_0.95M_0.05O₃（M=Ce、Y、La、Al）solid solutions were prepared by combustion method.The experimental results show that the doped ions successfully enter the BaCeO₃lattice with good crystallinity.The capacity retention rates of undoped BaCeO₃and doped Y³⁺,La³⁺and Al³⁺samples were 22.8%,24.4%,27.0%and 16.2%respectively.La³⁺doping increases the solid solution capacity retention and hydrogen diffusion coefficient.