Influence Of Ion Doping On The Properties Of Ni-BaCeO₃ Based Hydrogen Separation Membranes

With gradual depletion of the traditional fossil fuels,the importance of new energydevelopment has become increasingly necessary.Hydrogen energy has attracted a lot of attention because of its high thermal value,clean reaction product and extensive sources（fossil fuels,biomass energy and solar energy）.The hydrogen should be separated from the mixture gas which is obtained from the raw materials.Among them,proton-electron mixed conducting hydrogen separation membrane is one of the hot spot of current re-search,because of the high separation efficiency and low price.Among the high tem-perature proton conducting oxides,though the Ba Ce O₃-based proton conductors possess the highest conductivity,they show poor chemical stability,which leads to a poor chemical stability of Ni-Ba Ce O₃ based hydrogen separation membrane.The doping of Zr can improve its chemical stability,but it leads to the decrease in conductivity and sinterability.Upon this,this thesis studied the properties of the Ba Ce O₃-based proton conductor doped with In,Ta,Gd,Tb,Y and Ni-Ba Ce O₃ based hydrogen separation membrane doped with In,Ta,Y.In,Ta co-doped Ba Ce O₃-based proton conductors were fabricated by citrate method and modified citrate method.The chemical stability in H₂O and CO₂ atmosphere,as well as the conductivity in wet 10%H₂,was tested.The results indicate that In-doping not only can improve the sinterability of the sample,but also the sinterability increases with the In content increasing,while Ta-doping decreases the sinterability of the sample.Single In-doping can improve the chemical stability of the sample in H₂O,but has little effect on the stability of the powder sample under high concentration of CO₂.Co-doping with In and Ta can greatly improve the chemical stability of the sample in CO₂,and the chemical stability increases with the Ta content increasing.However,co-doping with In and Ta decreases the proton conductivity of Ba Ce O₃-based proton conductor,and the proton conductivity decreases continuously as a function of the doping content.The conductivity of BCI25Ta5 at 800℃is 1.16^′10^-3S/cm.the prepared Ba Ce O₃-based proton conductors with In,Ta,Y co-doping were mixed with Ni,and then sintered in 5%H₂/95%Ar environment to fabricate the dense cermet hydrogen separation membranes.The results indicate that the conductivity of the sample increases with the temperature increasing and the conductivity in wet 10%H₂ is higher than that in dry air and wet N₂.Moreover,in dry air and wet N₂,the conductivity of BCI10Ta10Y10 is higher than that of BCTa10Y20 and BCI20Ta10.The hydrogen per-meability of Ni-BCI10Ta10Y10 is lower than that of Ni-BCY30 between 700℃⁹00℃.However,the hydrogen permeability of Ni-BCI10Ta10Y10 is stable in 20%CO₂,while that of Ni-BCY30 decreases significantly,indicating that In and Ta co-doping decreases the hydrogen permeability of Ni-Ba Ce O₃ hydrogen separation membrane,but can im-prove its chemical stability.However,SEM and XRD results show that all samples have had a chemical reaction on the surface.In,Tb co-doping and In,Gd co-doping Ba Ce O₃-based proton conductors were fabri-cated.The results indicate that all samples have a poor chemical stability in H₂O and CO₂,which is similar to BCY.The single doping with Tb or Gd will increase the con-ductivity of the sample.In addition,the conductivity of In,Tb co-doping sample is slightly lower,while that of In,Gd co-doping sample has little change.