Study On Barium-Rich Perovskite Oxides Used As Electrodes For The Solid Oxide Fuel Cell

The solid oxide fuel cell(SOFC)is an energy conversion device that works at high temperature.It can realize the direct conversion of electrical and chemical energy.Furthermore,the conversion efficiency is high,and the device is entirely friendly to the environment.With the holding of the National People's Congress and the Chinese Political Consultative Conference(NPC&CPPCC),some hot words have gradually become the focus of people's discussion.Energy,as the lifeblood of the country,has become a high-frequency word during the conferences.The development of SOFC technology can,to a certain extent,alleviate the heavy demand for non-renewable energy such as fossil energy,and reduce greenhouse gas and sulfur oxide and nitrogen oxide emissions by changing the energy structure.The main challenges faced by SOFC are as follows:the lowering operating temperature which leads to the increased cathode impedance,and another problem that the anode is less adaptable to carbon-based fuels.Both of these problems result in lower power output of the entire cell.With the evolution of various human technologies,rare earth elements have been discovered,explored and separated by human beings,and gradually become crucial to lots of contemporary high-tech new materials.However,due to their geochemical properties,rare earth elements are rarely enriched to the extent that they could be economically exploited.Besides,they are not an inexhaustible resource so that the strategic value and economic value are equally important.Therefore,it is of great significance to actively explore new oxides to replace rare earth element oxides.To research new solid oxide fuel cell's electrode materials,the superconducting material Ba₂MCu₃O₆₊d(M=Y,Gd,Ho and Eu)and BaMnO₃-based perovskite type oxides have been systematically studied in different working modes in solid oxide fuel cells.We tested the relevant performance and analyzed the mechanism.The Ba₂MCu₃O₆₊d(M=Y,Gd,Ho and Eu)powders were prepared by the combustion method,and the effect of different rare earth elements doping to the phase formation was studied.Also,the electrical conductivity and stability of the materials in an oxidizing atmosphere were studied.We analyzed the action mechanism of different rare earth elements doping,studied the stability of the oxide structure and tested the electrochemical performance.Electric conductivity higher than 200 S cm^-1 at a temperature below 200 ^oC was obtained for the Ba₂MCu₃O₆₊dsamples but it decreased dramatically along with the heating process.However,the conductivity was higher than74 S cm^-1 at 600 ^oC.The conductivity of Ba₂YCu_2.6Fe_0.4O₆₊dat 600 ^oC was close to 22S cm^-1.Compared with Ba₂YCu₃O₆₊d,the conductivity decreased with the amount of Fe content as the temperature rose up to 800 ^oC in the air.For the anode materials,the conductivity of BaMnO₃,Ba Mn_0.75Fe_0.25O_3-dand Ba Mn_0.75Fe_0.2Ru_0.05O_3-dboth in the air and in 5%H₂/Ar increased with increasing temperature.The overall conductivity of BaMnO₃ at a reducing atmosphere was greater than that in the air.At 800 ^oC,the conductivity in the air and in the reducing atmosphere was 0.004 and 0.04 S cm^-1,respectively,an increase of about an order of magnitude.The conductivity of Ba Mn_0.75Fe_0.25O_3-dand Ba Mn_0.75Fe_0.2Ru_0.05O_3-din the air was 0.06and 0.03 S cm^-1,respectively and 0.011 and 0.012 S cm^-1 in 5%H₂/Ar.The OCVs of the cells with Ba Mn_0.75Fe_0.25O_3-dand Ba Mn_0.75Fe_0.2Ru_0.05O_3-danodes are above 1.0 V,and the peak power reached 230 and 240 m W cm^-2,repectively.The R_s value of Ba Mn0.75Fe0.2Ru0.05O3-dwas smaller than that of Ba Mn0.75Fe0.25O3-d.With propane as fuel,the OCV decreased to 0.89 and 0.95 V for Ba Mn_0.75Fe_0.25O_3-dand Ba Mn0.75Fe0.2Ru0.05O3-d.The performance of cells with Ba Mn0.75Fe0.25O3-dand Ba Mn0.75Fe0.2Ru0.05O3-danodes declined to different degrees when the stability testing was performed in propane at an applied voltage of 0.6 V and the Ba Mn_0.75Fe_0.2Ru_0.05O_3-done showed a large fluctuation.