Performance of a PEM water electrolyser using a TaC-supported iridium oxide electrocatalyst

Polymer electrolyte membrane (PEM) water electrolysis is an attractive way of producing carbon-free hydrogen. One of the drawbacks of this method is the need for precious metal-based electrocatalysts. This calls for a highly efficient utilization of the precious metal, which can be obtained by dispersing the precious metal compound onto a catalyst support. Electrocatalysts with 50, 70 and 90 wt.% of IrO₂ on a TaC support were tested in a laboratory PEM water electrolyser and compared with pure IrO₂. The temperature was set at 90, 110, 120 and 130 °C respectively and the cell voltage was varied between 1.4 and 1.8 V. The load characteristics and electrochemical impedance spectra were obtained and compared for a range of electrocatalysts. The highest current densities and the lowest charge transfer and cell resistances were found for the 70 wt.% IrO₂ electrocatalyst. By contrast, the pure IrO₂ electrocatalyst showed the lowest current densities and the highest charge transfer and cell resistance. For example, the relative difference in current densities between the 70 wt.% IrO₂ and the pure IrO₂ electrocatalyst attained 36% at 130 °C and 1.7 V. All of the supported electrocatalysts showed a higher efficiency of utilization of the precious metal than the pure IrO₂.