Effect of the La/W ratio in lanthanum tungstate on the structure, stability and hydrogen permeation properties

Lanthanum tungstates are the kind of attractive mixed proton-electron conductive (MPEC) oxides, which can be used as the hydrogen permeable membrane with almost infinite hydrogen selectivity in dry hydrogen-containing atmosphere theoretically. A series of lanthanum tungstates with different La/W ratios, La5.3WO11.25-delta (LWO53), La5.4WO11.25-delta (LWO54), La5.5WO11.25-delta (LWO55) and La5.6WO11.25-delta (LWO56), were prepared through a solid-state reaction method and the effect of La/W ratio on the membrane structure, stability and hydrogen permeation properties have been investigated. A pure cubic phase can be formed gradually with the increase in calcination temperature for lanthanum tungstates. The phase formation temperature increases with the increase in the La/W ratio, and a higher oxygen absorption capacity can be achieved in lanthanum tungstate with a higher La/W ratio. The hydrogen permeation flux through the lanthanum tungstate membranes increases slightly with an increase in La/W ratio, while the stability decreases. The lanthanum tungstate membrane with a La/W ratio of 5.5 may be a good candidate for hydrogen separation applications because of its favorable balance between stability and hydrogen permeability.