Chemical deposition of platinum nanoparticles on iridium oxide for oxygen electrode of unitized regenerative fuel cell

Platinum nanoparticles were deposited on the surface of IrO2 by chemical reduction. The morphology and structure of nanostructural Pt/IrO2 composites were characterized by XRD, EDX and FE-SEM. The reduction of PtCl62- ions in sodium borohydride aqueous solution containing sodium dodecylbenzenesulfonate (SDBS) additive leads to a fine dispersion and high loading of platinum nanoparticles on IrO2 without serious aggregation. A slight up-shift of the 2θ values in XRD patterns indicates some interaction between IrO2 and Pt nanoparticles in the sizes of ca. 10–20 nm. As bifunctional electrocatalyst for oxygen electrode, IrO2-supported Pt exhibits slightly lower oxygen reduction reaction (ORR) activity but markedly higher oxygen evolution reaction (OER) activity than a mixture of Pt and IrO2. It could be explained by the downshift of the d-band center (∈d) through the d-band coupling model and resulting weak O2 molecule adsorption on Pt catalysts supported by IrO2.