| Implementation of hydrogen economy requires establishment of a whole supply chain,including hydrogen production,purification,storage,utilization,and recovery.It remains challenging to selectively purify hydrogen out of H2-containing streams,especially when H2 concentrations is low.High-temperature proton conductive ceramic hydrogen separation membranes show favorable advantages over the traditional separation technologies,such as low energy consumption,good operation stability,high mechanical strength,simple operation and low materials costs.However,the hydrogen separation performance of the current ceramic membranes cannot meet the practical needs in industrial applications.It is urgent to develop a novel protonic ceramic membrane for hydrogen separation with optimal conductivities and well-tailored microstructures so as to reduce the bulk proton transport resistances and the surface hydrogen exchange resistances.In this study,we prepared dual phase hydrogen separation ceramic membranes and ceramic hydrogen pumps to realize the efficient separation of hydrogen,by the tape casting and tape-lamination methods with Ba Zr0.1Ce0.7Y0.2O3-??BZCY?as the protonic conductor.Firstly,we prepared a series of proton conductor fuel cell cathode material powders by solid state reaction and sol-gel methods,and only Sr Fe0.75Mo0.25O3-??SFM?and Gd0.2Ce0.8O2-??GDC?were suitable for the hydrogen separation ceramic membrane by the characterization of X-ray diffraction,thermal expansion analysis,and conductivity measurement.Then we combined BZCY and SFM?GDC?to prepare the dual phase hydrogen separation ceramic membranes with“porous|dense|porous”structure to research the hydrogen separation performance of the ceramic membranes.The hydrogen separation performance of the“porous BZCY/SFM55|dense BZCY/SFM55|porous BZCY/SFM55”membrane was much lower than expected due to the poor catalytic activity after high temperature sintering.Using Ni O/BZCY as porous support layer could greatly improve the hydrogen separation performance due to the excellent catalytic activity of the metal Ni obtained by in-situ reduction;the separation rate reached 3.1 m L·cm-2·min-1at 750?and 2.9 m L·cm-2·min-1 even at500?.Secondly,the driving force for hydrogen separation of the dual-phase ceramic membrane is the difference in hydrogen concentration,the separation of hydrogen cannot be achieved when the hydrogen concentration in the raw gas is low;while the driving force for hydrogen separation of the electrochemical hydrogen pump is the external electric field,which can achieve controllable and efficient hydrogen separation across concentration gradient.So we prepared ceramic hydrogen pumps with“porous Ni O/BZCY|dense BZCY|porous Ni O/BZCY”structure,and then optimized the reduction treatment conditions of the ceramic hydrogen pumps.It was found that the Ni particles reduced at 500?contained a large number of nanopores with a mean pore size of about 70nm.With the reducing temperature rising to 700?,the nanopores within the Ni particles continuously collapsed and disappeared.The sintering and shrinking of Ni particles gradually increased the gap between Ni and BZCY particles,preventing the charge transfer reactions between Ni and BZCY.So the hydrogen pumping flux for the pump reduced at low temperature?such as 500°C,denote as HP500?was almost 3 to 4 times higher than that for the pump reduced at high temperature?such as 700°C,denote as HP700?;the hydrogen pumping flux could reach15.8 m L·cm-2·min-1 from 50%H2-50%N2 mixture at 500°C,and the energy consumption was as low as 1.62k Wh/m3 H2,with the Faradic efficiency almost 100%.The hydrogen pumping flux decreased with decreasing the hydrogen concentration in the feedstock,The hydrogen pumping flux and the recovery yield were 6.4 m L·cm-2·min-1and 68%for HP500 operating on 10%H2-90%N2 at 500?,respectively.With the feedstock switching to 10%H2-90%CH4,the pumping flux and the recovery yield of HP500 decreased to 3.65m L·cm-2·min-1and 39%,respectively.Thirdly,we prepared the single protonic fuel cell scaffold with“porous Ni O/BZCY|dense BZCY|porous BZCY”structure,and then the double-perovskite Ba Gd0.8La0.2Co2O6-??BGLC?nanoparticles were impregnated into the porous BZCY scaffolds as the s air electrodes.The resulting fuel cells showed excellent performance with the maximum power density as high as 1.20W·cm-2 at 750?,or 0.43W·cm-2 at500?.In addition,such cells also showed excellent characteristics in the electrolysis mode.The electrolytic current densities under 1.3V were 0.28 and 1.22A·cm-2 at 500and 700?,respectively.Furthermore,these cells had excellent cycling reversibility between the fuel cell and the electrolysis modes.In particular,no noticeable degradation was observed after a 5-cycle measurement with a total duration of 50 h. |
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