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).