Water Electrolysis Using a Porous IrO2/Ti/IrO2 Catalyst Electrode and Nafion Membranes at Elevated Temperatures

Porous IrO2/Ti/IrO2 catalyst electrodes were obtained by coating IrO2 on both sides of three types of porous Ti powder sheets (sample 1, sample 2, and sample 3) using different surface treatment methods, and a hydrogen evolution catalyst electrode was obtained by coating Pt/C on carbon gas diffusion layers. A Nafion115 membrane was used as an electrolyte for the membrane electrode assemblies (MEA). Water electrolysis was investigated at cell temperatures up to 150 degrees C, and the electrical characteristics of the three types of porous IrO2/Ti/IrO2 catalyst electrodes were investigated. The sheet resistance of sample 1 was higher than those of samples 2 and 3, although during water electrolysis, a high current density was observed due to the nanostructure of the IrO2 catalyst. In addition, the structural stabilities of Nafion and Aquivion membranes up to 150 degrees C were investigated by using small angle X-ray scattering (SAXS). The polymer structures of Nafion and Aquivion membranes were stable up to 80 degrees C, whereas the crystalline domains grew significantly above 120 degrees C. In other words, the initial polymer structure did not recover after the sample was heated above the glass transition temperature.

Automated summary

The electrical characteristics of porous IrO2/Ti/IrO2 catalyst electrodes during water electrolysis were investigated, with sample 1 showing higher sheet resistance than samples 2 and 3; the structural stabilities of Nafion and Aquivion membranes up to 150 degrees C were studied, revealing irreversible changes in polymer structure above certain temperatures.