Nanoparticle-Modified Electrode with Size- and Shape-DependentElectrocatalytic Activities.

The size, shape, composition, andcrystalline structures of noblemetal nanoparticles are the key parameters in determining their electrocatalyticperformance. Here, we report on a robust chemical-tethering approachto immobilizing gold nanoparticles onto transparent indium tin oxide(ITO) glass electrode surfaces to systematically investigate theirsize- and shape-dependent electrocatalysis toward a methanol oxidationreaction (MOR) and an oxygen reduction reaction (ORR). Monodisperse20 nm nanospheres (NS20s), 45 nm nanospheres (NS45s), and 20 nm ×63 nm nanorods (NRs), which could be chemically tethered to ITO-surface-formingsubmonolayers without any aggregation, were synthesized. These nanoparticle-modifiedITO electrodes exhibited strong electrocatalytic activities towardMOR and ORR, but their mass current densities were highly dependenton the particle sizes and shapes. For particles with similar shapes,the size determined the mass current densities: smaller particle sizesled to greater catalytic current densities per unit mass because ofthe greater surface-to-volume ratio (NS20s > NS45s). For particleswith comparable sizes, the shape or crystalline structure governedthe selectivity of the electrocatalytic reactions: NS45 exhibiteda higher mass current density in MOR than did NRs because its dominant(111) facets were exposed, whereas NRs exhibited a higher mass currentdensity in ORR because its dominant (100) facets were exposed. [ABSTRACT FROM AUTHOR]