Enhanced H2 Separation through Mixed Proton Electron Conducting Membranes Based on La5.5W0.8M0.2O11.25 d

Abstract

La5.5WO11.25- is a proton-conducting oxide that shows high protonic conductivity, sufficient electronic conductivity, and stability in moist CO2 environments. However, the H-2 flows achieved to date when using La5.5WO11.25- membranes are still below the threshold for practical application in industrial processes. With the aim of improving the H-2 flow obtained with this material, La5.5WO11.25- was doped in the W position by using Re and Mo; the chosen stoichiometry was La5.5W0.8M0.2O11.25-. This work presents the electrochemical characterization of these two compounds under reducing conditions, the H-2 separation properties, as well as the influence of the H-2 concentration in the feed stream, degree of humidification, and operating temperature. Doping with both Re and Mo enabled the magnitude of H-2 permeation to be enhanced, reaching unrivaled values of up to 0.095mLmin(-1)cm(-2) at 700 degrees C for a La5.5W0.8Re0.2O11.25- membrane (760m thick). The spent membranes were investigated by using XRD, SEM, and TEM on focused-ion beam lamellas. Furthermore, the stability in CO2-rich and H2S-containing atmospheres was evaluated, and the compounds were shown to be stable in the atmospheres studied.