Proton exchange membrane water electrolysis with short-side-chain Aquivion® membrane and IrO2 anode catalyst

• Proton exchange membrane electrolysis cell investigated at temperatures to 120 °C.
• Short side-chain Aquivion® membrane based electrolyser MEAs.
• Cell voltage at 120 °C of 1.57 V at 1 A cm−2.
• Sulfonated hydrocarbon membrane operated in PEM electrolysis to 120 °C.

A series of three membrane types has been screened for medium temperature solid polymer electrolyte water electrolysis in membrane electrode assemblies coated with 2 mg cm−2 of iridium oxide as a catalyst for the oxygen evolution reaction, synthesised via a hydrolysis method from the hexachloroiridic acid precursor, and deposited on the membrane either directly by spray deposition or by decal transfer. The short-side-chain perfluorosulfonic acid Aquivion® ionomer of equivalent weight 870 meq g−1, in membranes of thickness 120 μm, gives higher water electrolysis performance at 120 °C than a composite membrane of Aquivion® with zirconium phosphate, while a sulfonated ether-linked polybenzimidazole, sulfonated poly-[(1-(4,4′-diphenylether)-5-oxybenzimidazole)-benzimidazole], shows promising performance and no transport limitations up to 2 A cm−2. The lowest cell voltage was observed at 120 °C for an MEA prepared using spray-coating directly on the Aquivion® membrane, 1.57 V at 1 A cm−2.