Abstract
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 °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 °C were investigated by using small angle X-ray scattering (SAXS). The polymer structures of Nafion and Aquivion membranes were stable up to 80 °C, whereas the crystalline domains grew significantly above 120 °C. In other words, the initial polymer structure did not recover after the sample was heated above the glass transition temperature.
Highlights
Global warming is driving societies that burn fossil fuels for energy, which produces huge amounts of CO2, towards renewable and sustainable energies
A Nafion115 membrane was sandwiched between the porous IrO2 catalyst electrode and the Pt/C carbon electrode, and membrane electrode assemblies (MEAs) were prepared by using a hot press method
Three types of porous IrO2/Ti/IrO2 catalyst electrodes prepared by coating IrO2 (7.5 mg/cm2) on both sides of Ti powder porous sheets under different surface treatment conditions were obtained from Gunma, Japan Calit Co., Ltd
Summary
Global warming is driving societies that burn fossil fuels for energy, which produces huge amounts of CO2, towards renewable and sustainable energies. PEMWE, in which a proton exchange membrane and a noble metal catalyst electrode are used, has a higher hydrogen production cost (4.1–8.6 €/kg H2). It was speculated that the three-dimensionally coated IrO2 catalyst electrode would be a useful method for improving catalytic performance and system construction for water electrolysis. A Nafion115 membrane was sandwiched between the porous IrO2 catalyst electrode and the Pt/C carbon electrode, and membrane electrode assemblies (MEAs) were prepared by using a hot press method. Three types of porous IrO2/Ti/IrO2 catalyst electrodes prepared by coating IrO2 (7.5 mg/cm2) on both sides of Ti powder porous sheets (thickness = 0.5 mm, porosity = 57–61%) under different surface treatment conditions were obtained from Gunma, Japan Calit Co., Ltd. MEAs were obtained by hot pressing at 130 ◦C and 9.8 kN for 20 min
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