Preparation And Electrochemical Performance Of Gd、Sc Co-Doped BaZrO₃ Proton Conductor

Solid Oxide Fuel Cell（SOFC）is regarded as a promising chemical-to-electrical energy transformation devices due to its high efficiency and environmental friendliness,and therefore attracted widespread attention all over the world.High operating temperature is the biggest obstacle to the commercialization of SOFC.Under conditions of low temperature,proton conductive solid oxide electrolysis cell（H-SOFC）has a good performance,H-SOFC thus provides an effective and feasible way to reduce the operating temperature of the fuel cell.Doped BaZrO₃proton conductor under an oxygen partial pressure has a relatively wide high ion conductivity and excellent chemical stability,but poor activity sintering,preparation is difficult,low grain boundary conductivity,which limits its application of H-SOFC.This paper mainly studies the influence of Zr site multi-element doping on the structure,sintering activity and conductivity of BaZrO₃proton conductor.On this basis,the influence of sintering aid Ni O on the sintering performance and conductivity of BaZrO₃proton conductor is studied.First,mechanical ball milling combined with high temperature and atmospheric sintering was used to prepare Sc and Gd co-doped Ba Zr_0.8Gd_0.2-xSc_xO_3-δ（BZGd Sc）ceramic,and the phase structure and sintering properties of Sc and Gd co-doped Ba Zr O3 matrix subconductors were investigated.Studies have shown that BZGd Sc has a good single cubic perovskite structure.With the increase of Sc doping,the sintering performance of BZGd Sc is improved.The average grain size of the sample sintered at 1600℃grows from about 1.5μm when Sc is 0to more than 5μm when Sc is 0.15.The relative density of ceramics has correspondingly increased from 95%to 98.74%.Although Gd-doped BaZrO₃exhibits high grain conductivity,its lower grain boundary conductivity results in a smaller total conductivity.With the further increase of Sc doping,the total conductance of Ba Zr_0.8Gd_0.2-xSc_xO_3-δceramics are all improved.At 750℃,the electrical conductivity of Ba Zr_0.8Sc_0.2O_2.9in three atmospheres of dry air,humid air and humid hydrogen are 1.724×10^-2S·cm^-1,1.651×10^-2S·cm^-1and 1.831×10^-3S·cm^-1,respectively.This indicates that the co-doping of Gd and Sc is one of the effective measures to improve the sinterability and conductivity of BaZrO₃proton conductor.Secondly,through a comparative study of trace Ni doping and as a sintering aid,the effect of Ni O addition on the conductivity of Ba Zr_0.8Gd_0.2-xSc_xO_3-δ（BZGd Sc）electrolyte was investigated.The results show that the addition of 1wt%Ni O can improve the sintering activity of the electrolyte to a certain extent and increase its electrical conductivity.When Ni O is used as a dopant,the conductivity of the electrolyte is higher than when Ni O is used as a sintering aid.When 1%Ni is doped at the Zr site,the conductivity of BZGd Sc-Ni electrolyte can reach1.403×10^-2S·cm^-1,1.960×10^-2S·cm^-1and 2.864×10^-3S·cm^-1under three atmospheres of dry air,humid air and humid hydrogen.This indicates that a small amount of Ni doping can make the crystal grains grow uniformly and increase the grain boundary conductivity,Furthermore,it has a certain improvement effect on the electrochemical performance of the BaZrO₃proton conductor.