Hydrogen Permeability Of Pr,In Doped BaZrO₃ Proton Conductor

In order to achieve the goal of carbon peaking,the development of new energy sources is of great importance to the development of the world.Hydrogen is an important clean energy source,however,there are many impurity gases produced by industrial hydrogen production,which makes the research of hydrogen separation membranes gradually step into people’s view.In the field of hydrogen separation membranes,mixed conductor hydrogen separation membranes are characterized by simple structure,good mechanical properties and 100%selectivity for hydrogen due to their proton conduction properties.As an important material for hydrogen separation membranes,Ba Zr O₃has good stability,and the conductivity and the hydrogen permeation performance of the membrane can be improved by doping.In view of this,oxygen vacancy,conductivity and hydrogen permeability of ionic doped Ba Zr O₃-based conductors are studied.The phase structure,microscopic morphology and oxygen vacancy concentration of Pr³⁺and In³⁺doped Ba Zr_0.8Y_0.2O_3-δ（BZY）proton conductors were characterized,and their conductivity under different atmospheres,as well as hydrogen permeability performance and stability tests were investigated.The results show that Pr³⁺and In³⁺doping can not only increase the grain size and improve the sintering activity of BZY,and but also increase the oxygen vacancy concentration.Due to the higher concentration of oxygen vacancies,In³⁺doped BZY has the highest conductivity.All samples have the highest conductivity in air,indicating that the samples are dominated by oxygen ion conduction.To further analyze the proton conductivity of the material,a proton-electron mixed conducting hydrogen separation membrane was prepared by external short circuiting.The results show that the In³⁺doped BZY possesses the highest hydrogen permeation flux due to its maximum electrical conductivity.It is also shown that the increase in temperature,hydrogen partial pressure,and wet atmosphere have positive effects on the hydrogen permeation performance.In addition,the Wagner equation was used to calculate the proton conductivity.The analysis shows that the calculated proton conductivity is one order of magnitude lower than the total conductivity,which indicates that the material has other conductive behaviors in addition to proton conductivity.In order to analyze the stability of the material,the ceramic film was subjected to boiling water and CO₂.The Pr³⁺and In³⁺doped BZY still maintains its original structure and morphology,indicating its good stability.Pr³⁺and In³⁺doped Ba Zr O₃ were prepared by the sol-gel method,and the effects of Pr³⁺doping concentrations on the material properties were investigated.The results show that the grain size of the samples increases with the increase of Pr³⁺doping concentration,which indicates that the Pr³⁺doping could improve the sintering activity.In addition,the oxygen vacancy concentration increases with the increase of Pr³⁺.It is noteworthy that the highest conductivity is achieved at a Pr³⁺doping concentration of 20%,while when the Pr³⁺doping concentration was 30%,the conductivity of the samples decreases instead,which may be caused by the excessive oxygen vacancies leading to defect conjugation.Different from Pr³⁺and In³⁺doped BZY,Pr³⁺and In³⁺co-doped BZ has the highest conductivity in hydrogen atmosphere,indicating that its conductivity is mainly proton conduction.Ba Zr_0.9-xPr_xIn_0.1O_3-δmetal-ceramic hydrogen separation membranes were prepared using Pt as the electron conducting phase,and their hydrogen permeation properties were investigated.Among them,the hydrogen permeation flux is maximum when the Pr³⁺doping concentration is 20%,which is attributed to its better sintering activity as well as oxygen vacancy concentration.Similarly,the hydrogen permeation flux decreases slightly when the Pr³⁺doping concentration reaches 30%,which may be due to the large difference in the radii of Pr³⁺and Zr⁴⁺,the large lattice distortion caused by the excessive doping and defect association.Because the hydrogen permeation process is controlled by bulk diffusion,hydrogen permeation performance is greatly improved when hydrogen separation membrane is an asymmetric membrane with a thinner effective membrane thickness.The hydrogen permeation fluxes,structure and morphology of each hydrogen separation membrane remain unchanged after introducing CO₂,showing good stability.