A mixed protonic-electronic conductor made of La5.5W0.45Nb0.15Mo0.4O11.25-delta (LWNM) has been developed by partial co-substitution of W with Nb and Mo in La5.5WO11.25 (- delta) aiming to improve the hydrogen permeation property. A hydrogen permeation flux of 0.195 mL/mim.cm(2) was obtained at 1000 degrees C with a mixture of 50% H-2-50% He as the feed gas under dry condition. More importantly, there was no obvious decline of the hydrogen flux during 80 h operation even with CO2 in the feed gas. (C) 2016 Elsevier B.V. All rights reserved.