Investigation of supported IrO₂ as electrocatalyst for the oxygen evolution reaction in proton exchange membrane water electrolyser

Indium tin oxide (ITO) was used as a support for IrO₂ catalyst in the oxygen evolution reaction. IrO₂ nanoparticles were deposited in various loading on commercially available ITO nanoparticle, 17-28 nm in size using the Adam's fusion method. The prepared catalysts were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The BET surface area of the support (35 m ²/g) was 3 times lower than the unsupported IrO₂ (112.7 m²/g). The surface area and electronic conductivity of the catalysts were predominantly contributed by the IrO₂. The supported catalysts were tested in a membrane electrode assembly (MEA) for electrolyser operation. The 90% IrO₂-ITO gave similar performance (1.74 V@1 A/cm²) to that of the unsupported IrO₂ (1.73 V@1 A/cm²) in the MEA polarisation test at 80 C with Nafion 115 membrane which was attributed to a better dispersion of the active IrO₂ on the electrochemically inactive ITO support, giving rise to smaller catalyst particle and thereby higher surface area. Large IrO₂ particles on the support significantly reduced the electrode performance. A comparison of TiO₂ and ITO as support material showed that, 60% IrO₂ loading was able to cover the support surface and giving sufficient conductivity to the catalyst.