Preparation And Properties Of Mixed Proton-Electron Conducting Dual Phase Ceramic Membranes For Hydrogen Permeation

The low electronic conductivity of conventional perovskite-type proton conductor restricts the hydrogen permeability of ceramic membrane, thus searching for appropriate method to improve the ceramic membrane electronic conductivity is the priority challenge in enhancing the hydrogen permeability.In this work, Sr Ce0.95Y0.05O3-α(SCY) was chosen as the fundamental proton conductor material, and the hydrogen permeability was explored to improve by two ways:(a) Metal Ag was selected as electronic conductive phase to prepare Ag-SCY dual-phrase membrane;(b) The metallic oxides were selected as electronic conductive phase, such as Ni Fe2O4,La Cr O3,Zn O to prepare dual-phrase membrane. The perovskite structure SCY power and SCY/metallic oxides compound were prepared via Sol-gel low-temperature combustion method and Physics mixing method. The power was compressed into sheet blank through Solid dry pressing method and then sintered to get the dense ceramic membrane. The dense ceramic membranes were investigated by XRD, SEM, Digital Source-meter and GC for phase composition, chemical compatibility, microstructure, electrical conductivity and hydrogen separation. The stability was investigated at H2, boiling water and high temperature-CO2 atmospheres. The results showed as followed:SCY was prepared successfully with perovskite-type structure. Due to Zn O and SCY provide excellent chemical compatibility, Zn O was chosen as electronic conductive phase in ceramic membrane. After sintering at 1400℃with 4h, SCY form the compact structure while Zn O/SCY dual-phrase membrane was sintering at 1200℃. It indicated Zn O not only improve the electronic conductivity but also reduce the sintering temperature.The result of conductivity tests showed that both the doping content of Zn O and atmosphere had significant effect. With the doping ratio increase the electronic conductivity enhanced. At different atmosphere, the same conducting rule of dual-phrase membrane and SCY membrane could be observed σH2>σair>σwet ai>σN2 with Zn O doping ratio less than 20%.The results of hydrogen permeation of SCY, Ag-SCY, Zn O/SCY membranes indicated that with the permeation temperature arising, the compound flux and sweep gas rate increasing the hydrogen permeation flux increase. Ag-SCY dual-phrase membrane had the best permeation performance of 0.073 m L·min-1·cm-2 at 900 ℃,compound gas flux 126 m L·min-1, sweep gas flux 142 m L·min-1.The results of stability tests revealed that SCY powder was unstable with boiling water or CO2 at high temperature, but sintered SCY ceramic membrane showed certain stability. It could be attributed to the doping of Zn O into SCY, which at the same time was reducing its stability at H2 atmosphere.