High temperature operation of a composite membrane-based solid polymer electrolyte water electrolyser

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 1.2 A cm−2 at a terminal voltage of 1.9 V for Nafion–SiO2 and Nafion 115, respectively, at 100 °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).