The high temperature behaviour of a solid polymer electrolyte (SPE) water electrolyser based on a composite Nafion-SiO2 membrane was investigated and compared to that of a commercial Nafion membrane. The SPE water electrolyser performance was studied from 80 to 120, C with an operating pressure varying between 1 and 3 bar abs. IrO2 and Pt were used as oxygen and hydrogen evolution catalysts, respectively. The assemblies were manufactured by using a catalyst-coated membrane (CCM) technique. The performance was significantly better for the composite Nafion-SiO2 membrane than commercial Nafion 115. Furthermore, the composite membrane allowed Suitable water electrolysis at high temperature under atmospheric pressure. The current densities were 2 and 1.2A cm(-2) at a terminal voltage of 1.9 V for Nafion-SiO2 and Nafion 115, respectively, at 100 degrees C and atmospheric pressure. By increasing the temperature up to 120 C, the performance of Nafion 115 drastically decreased whereas, the cell based on Nafion-SiO2 membrane showed a further increase of performance, especially when the pressure was increased to 3 bar abs (2.1 A cm(-2) at 1.9 V). (c) 2008 Elsevier Ltd. All rights reserved.