Study of mixed Pr/La molybdates, La5.4-xPrxMo1-yNbyO12-δ, for hydrogen separation membranes.

Abstract

Lanthanide molybdates, with general formula Ln5.4MoO11.1-, are materials with mixed proton-ionic conductivity that can be used as hydrogen separation membranes. Their symmetry (cubic or rhombohedral) depends on the synthetic conditions and composition [1-2]. In this work, it has been studied the influence of praseodymium and niobium doping on the La5.4-xPrxMo1-yNbyO12- (x= 1.35, 2.7, 4.05, 5.4; y= 0, 0.1) series, with two main objectives: i) increase the electronic conductivity (praseodymium doping) and ii) increase the amount of oxide ion vacancies and enhance the ionic conductivity (niobium doping). The materials have been prepared by the freeze-drying method and characterised by X-ray diffraction (Rietveld method), X-ray photoelectron spectroscopy, scanning electron microscopy and complex impedance spectroscopy.