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In this paper, an effective approach is demonstrated for the fabrication of IrO 2 -decorated polystyrene@functionalized polypyrrole (core@shell; PS@PPyNH 2 ) microspheres. The synthesis begins with the preparation of monodispersive PS microspheres with a diameter of 490 nm, by a process of emulsifier-free emulsion polymerization, followed by a copolymerization process involving pyrrole and PyNH 2 monomers in a PS microsphere aqueous suspension, to produce uniform PS@PPyNH 2 microspheres with a diameter of 536 nm. The loading of 2 nm IrO 2 nanoparticles onto the PS@PPyNH 2 microspheres can be easily adjusted by tuning the pH value of the IrO 2 colloidal solution and the PS@PPyNH 2 suspension. At pH 4, we successfully obtain IrO 2 -decorated PS@PPyNH 2 microspheres via electrostatic attraction and hydrogen bonding simultaneously between the negatively-charged IrO 2 nanoparticles and the positively-charged PS@PPyNH 2 microspheres. These IrO 2 -decorated PS@PPyNH 2 microspheres exhibit a characteristic cyclic voltammetric profile, similar to that of an IrO 2 thin film. The charge storage capacity is 5.19 mA cm −2 , a value almost five times greater than that of PS@PPyNH 2 microspheres. In addition, these IrO 2 -decorated PS@PPyNH 2 microspheres exhibit excellent cell viability and biocompatibility.

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