La0.7Sr0.3Cu0.2Fe0.8O3-x as Oxygen Transport Membrane for Producing Hydrogen via Water Splitting

Abstract

Oxygen transport membranes (OTMs) made of mixed oxygen ionelectron conductors can generate significant amounts of hydrogen and oxygen via water splitting at moderate temperatures (500- 900{degree sign}C). Hydrogen production by this method is nongalvanic, and the separated hydrogen is of high purity. This study focuses on results that were obtained with La0.7Sr0.3Cu0.2Fe0.8O3-δ (LSCF7328), one potential OTM material. This material is easily prepared, exhibits good mechanical properties, and is stable in severe gas conditions. In tests of LSCF7328 membranes, the measured hydrogen production rates varied linearly with temperature, indicating that the material undergoes no phase transition, while the thin-film LSCF7328 sample shows a slightly different slope change in the Arrhenius plot. Also determined were the effects of membrane thickness and a Pt-porous layer and the microstructure before and after the measurements. The highest hydrogen production rate, ≈11.4 cm3/min-cm2, was obtained with a ≈50 μmthick LSCF7328 membrane via water splitting at 900{degree sign}C. The effects of surface oxygen exchange kinetics and the importance of porous substrate materials are discussed.