Abstract
Titania powders were surface modified with gold and/or silver nanoparticles (NPs) by photodeposition method. Gold modified titania exhibited much higher photocatalytic activity during methanol dehydrogenation under UV irradiation than titania modified with monometallic silver and bimetallic Au–Ag NPs. Bimetallic photocatalysts exhibited either enhanced or reduced visible light activity, depending on properties of noble metal NPs, sequence of their deposition on titania, and properties of host titania. Though numerical simulation (3D-FDTD) showed strong plasmonic field enhancement at the interface between titania and bimetallic core(Au)–shell(Ag) NP, it is thought that co-deposition caused an enhancement of charge carriers recombination (by electron sinking in nearby second metal) inhibiting photoactivity under visible light irradiation. The highest level of photoactivity showed large rutile NPs with successively deposited metals, mainly in the form of individual monometallic NPs, due to size/shape polydispersity of deposited NPs, and thus with ability of light absorption in a broad wavelength range.
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