Gd-doped ceria enhanced triple-conducting membrane for efficient hydrogen separation

Abstract

Ceramic hydrogen separation membrane based on mixed protonic-electronic conductor has received considerable attention due to the advantage of 100% H2 selectivity. However, their widespread application faces two major hurdles including the limited hydrogen separation performance and chemical instability especially in CO2-containing atmospheres. Herein, using Gd-doped ceria (CGO) with excellent oxygen ionic conductivity to dope Sr-based hydrogen separation membrane, a novel triple-conducting (H+/O2−/e−) membrane Ce0.90Gd0.10O3−δ-SrCe0.95Fe0.05O3−δ-SrFe0.95Ce0.05O3-δ (CGO-SCF-SFC) was developed via automatic phase-separation of ceramic precursor after high temperature sintering, which showed both improved H2 separation performance and CO2-tolerance. The three chemically compatible phases CGO, SCF and SFC act as mainly oxygen-ionic conductor, protonic conductor and electronic conductor, respectively. The enhanced H2 flux with value of 0.54 mL min−1 cm−2 was achieved at 940 °C, which was attributed to two parts: (1) hydrogen separated as proton through SCF-SFC network; (2) hydrogen produced from water splitting that is enhanced by in situ oxygen removal through CGO phase. Moreover, benefiting from the suppression of CO2 adsorption and carbonate formation, a stable hydrogen separation flux of 0.33 mL min−1 cm−2 was obtained under CO2-containing atmospheres, indicating the enhanced CO2-tolerance of the triple-conducting (H+/O2−/e−) membrane CGO-SCF-SFC in comparison with the membrane SCF-SFC.