Dense Ceramic Membranes for Hydrogen Separation

Defects and Transport Properties in TiNb2O7

“…Depending on the detailed transport properties, proton conducting ceramics may serve as the functional component of membranes for hydrogen separation and as electrodes or electrolytes for Proton Conducting Fuel Cells . In a dense ceramic hydrogen separation membrane, mixed proton–electron conductivity is a prerequisite, since the hydrogen flux is governed by the so‐called ambipolar proton–electron conductivity, assuming fast surface kinetics . In most cases, mixed conduction can be found in proton conductors constituting reducible parent cations …”

Determination of the enthalpy of hydration of oxygen vacancies in Y-doped BaZrO3 and BaCeO3 by TG-DSC

“…in hydrogen gas separation membranes and protonic ceramic fuel cells (PCFC) [1][2][3]. Consequently, determination of reliable parameters for the hydration thermodynamics and the understanding of how these vary between different materials are important.…”

“…Empirical relations between the hydration parameters and other materials properties have been sought [4][5][6]. For ABO 3 perovskites the standard hydration enthalpy was on empirical basis proposed to be correlated with the difference in electronegativity between the B-and A-site cations [6]. From a recent study it seems that the apparent correlation relates to the absolute difference in electronegativity, i.e., it appears not to matter whether the A or B cation is the more electronegative [4].…”

Factors Limiting the Apparent Hydrogen Flux in Asymmetric Tubular Cercer Membranes Based on La27W3.5Mo1.5O55.5−δ and La0.87Sr0.13CrO3−δ

“…Dense metallic membranes based on Pd and its alloys show high solubility and diffusivity of hydrogen and are promising for hydrogen separation at intermediate temperatures (>~300–500 °C) [4,5]. On the other hand, dense ceramic membranes based on mixed proton and electron conducting materials demonstrate thermal and chemical stability for application in high temperature processes (>700 °C) [6,7], although their hydrogen fluxes are much lower than their metallic counterparts.…”

“…Mixed proton and electron conducting membranes based on perovskite-type materials, such as acceptor-doped SrCeO 3 and BaCeO 3 , suffer either poor stability, e.g., in CO 2 -containing atmospheres, or low hydrogen flux as a consequence of low electronic conductivity under relevant operational conditions [6,8,9,10,11]. Rare earth tungstates have attracted much attention due to their high chemical stability in CO 2 and H 2 S containing environments [12,13,14].…”