Preparation of alkaline earth element doped La2Hf2O7 materials and application in hydrogen separation

In order to improve the properties, alkaline earth element doped La1.95M0.05Hf2O7-5 (M = Ca, Sr, Ba) are prepared by high-temperature solid state method. The experimental results indicate that Ca is a suitable doping element. The prepared La2-xCaxHf2O7-5 (x = 0, 0.025, 0.05, 0.1) series samples are of pure pyrochlore structures. Among them, La1.95Ca0.05Hf2O75 has the densest structure, the highest conductivity, which is 2.86 x 10-3 S cm-1 in humid air at 800 degrees C, and outstanding chemical stability in H2O, CO2, H2 and 300 ppm H2S. The hydrogen separation performance of La1.95Ca0.05Hf2O7-5 membrane is tested using the external short-circuit method. The hydrogen permeation flux of 1.25 mm thick La1.95Ca0.05Hf2O7-5 membrane is 0.15 mL center dot min-1 center dot cm-2 in 70% H2/He feed gas at 900 degrees C. Humidification increases the hydrogen permeation flux and CO2 or H2S reduces the hydrogen permeation flux.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.