IrO2-deposited Pt electrocatalysts for unitized regenerative polymer electrolyte fuel cells

An IrO2/Pt electrocatalyst for the polymer electrolyte-type unitized regenerative fuel cell (URFC) was prepared by deposition of iridium oxide (IrO2) particles on Pt black via a colloidal iridium hydroxide hydrate precursor, and URFC performance was examined. After the iridium hydroxide hydrate deposited Pt was calcined at 400 °C in air for 1 h, rutile-structure IrO2particles (20–50 nm dia.) were formed on Pt particle clusters. TEM and pore volume distribution analysis revealed that the microstructure of the deposited IrO2/Pt catalyst was different from the mixed IrO2/Pt catalyst. The cell using the deposited IrO2/Pt (20 at % Ir) catalyst showed similar fuel cell performance with the mixed IrO2/Pt electrode of higher Pt content (10 at % Ir) while maintaining water electrolysis performance. Consequently, 51% round-trip energy conversion efficiency at a current density of 300 mA cm−2was attained.