PEM Water Electrolysis with Reduced Iridium Oxide Loadings : Influence on Kinetic Parameters and Electrolyser Performances

It is expected that PEM water electrolysis (PEMWE) will play a significant role in the hydrogen society as a key process for producing hydrogen from renewable energy sources. But before this, substantial cost reductions are still required. In a PEMWE cell, the oxygen evolution reaction (OER) occurs at high potential values and only few materials (usually platinum group metals) can be used as catalysts to avoid corrosion. In state-of-the-art, pure IrO2 is generally used as catalyst (with typical loadings of a few mg.cm). Reducing the catalyst loading can be achieved either by supporting the noble metal catalyst on a conducting support material; or by adding some inexpensive inert to form Ir-based composite oxide catalyst. However, along with the instability of most of those supports in oxidizing environment, the loadings of noble metal on these electrodes are still quite high (1.5-2.0 mg cm). According to the literature, iridium loadings can be reduced either by dispersion of oxide nano-particles on conducting support materials like titanium carbide, tantalum carbide and doped or reduced form of titanium or tin oxide; or by addition of some inexpensive inert materials such as TiO2 , SnO2 7 or TaxO2 8 , in order to form Ir-based composite oxide catalysts. However, in addition to the instability of most of these supports in oxidizing environments, iridium loadings on such electrodes remain significantly high (1.5-2.0 mg.cm).