Nd5.5W1−xUxO11.25−δ system: Electrochemical characterization and hydrogen permeation study

•The symmetry evolves from cubic to rhombohedral symmetry with increasing U contents and sintering temperatures.•Incorporation of U increases the total conductivity, becoming predominant oxygen ionic conductivity at high U%.•The enhanced oxygen ion transport is assigned to the U+6 reduction to U+4.•U additions allow reaching H2 flows due to H2 production via water splitting.•Crystalline symmetry depends on U contents and sintering temperatures.•U incorporation increases the total conductivity and the oxygen ion conductivity.

This work presents the structural and electrochemical characterization of mixed conducting materials based on the system Nd5.5W1−xUxO11.25−δ where x=0.1, 0.5 and 1. The evolution of the crystalline structure is studied as a function of the sintering temperature and the U content in the oxide lattice. The influence of hydration and pO2 as well as the H/D isotopic effect are studied by DC-electrochemical measurements under reducing environments. Hydrogen permeation is carried out for Nd5.5WO11.25−δ and Nd5.5W0.9U0.1O11.25−δ compounds in the range from 650 to 750 °C. Finally, stability of the developed materials at 800 °C is evaluated in contact with CO2-rich gas streams. This work completes previous reported studies on Ln6−xWO12−y based materials that show the possibility of engineering the conductivity properties of the Ln6−xWO12−y just by doping strategies.

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