Coupling of partial oxidation of methane (POM) with water dissociation in an oxygen transport membrane is a promising technology for methane utilization. However, cobalt based membrane materials show poor stability under the above harsh conditions. In this work, a nominal 60 wt % Ce0.8Sm0.2O2-delta-40 wt % Sr2Fe2.5Mo0.5O5+delta (CSO-SFMO) dual phase membrane is reported, which was synthesized by using a one-pot EDTA-citric acid complexing method. The phase structure and morphology of the CSO-SFMO membrane were characterized by XRD, SEM and EDXS. It was found that a uniform distribution of CSO phase with a fluorite structure and SFMO phase with a perovskite structure was achieved in the dual phase membrane. The CSO-SFMO membrane exhibited an improved stability compared with cobalt based perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta, (BSCF) membrane under CO2 or reductive gas atmospheres. The oxygen permeation flux of the dual phase membrane was investigated under different oxygen partial pressure gradients: air/He, air/CO2, air/POM, and H2O/POM. At 950 degrees C, the oxygen permeation fluxes of the CSO-SFMO membrane under air/POM and H2O/POM gradients were 2.7 cm(3) (STP) min(-1) cm(-2) and 0.75 cm(3) (STP) min(-1) cm(-2), respectively, which were much higher than the oxygen flux of 0.1 cm(3) (STP) min(-1) cm(-2) under air/He. Moreover, a CO selectivity of 98%, a CH4 conversion of 97% on the POM side and a H-2 production of 1.5 cm(3) (STP) min(-1) cm(-2) on the H2O splitting side were achieved in CSO-SFMO membrane reactor under the oxygen partial pressure gradient of H2O/POM, which was steadily run for 100 h before the measurement was intentionally stopped. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.