A set of high quality ceramics membranes manufactured by tape casting was used to explore the performance of BaCe0.5Zr0.3Y0.16Zn0.04O3-delta, (BCZYZ) as an electrolyte in electrochemical cells. The material has very good proton conductivity (2.1 mS cm(-1) at 600 degrees C), high transport proton number at T = 400-600 degrees C and can function well as the electrolyte in fuel cells or electrolysers using painted Pt as the electrodes. The co-electrolysis of CO2 and H2O to CO and H-2 has been shown to take place with Pt electrodes. (C) 2012 Elsevier B.V. All rights reserved.