Nanoplasmonically Engineered Interfaces on Amorphous TiO₂ for Highly Efficient Photocatalysis in Hydrogen Evolution

The nanoplasmonic metal-driven photocatalytic activity depends heavily on the spacing between metal nanoparticles (NPs) and semiconductors, and this work shows that ethylene glycol (EG) is an ideal candidate for interface spacer. Controlling the synthetic systems at pH 3, the composite of Ag NPs with EG-stabilized amorphous TiO₂ (Ag/TiO₂-3) was synthesized by the facile light-induced reduction. It is verified that EG spacers can set up suitable geometric arrangement in the composite: the twin hydroxyls act as stabilizers to bind Ag NPs and TiO₂ together and the nonconductive alkyl chains consisting only of two CH₂ are able to separate the two building blocks completely and also provide the shortest channels for an efficient transfer of radiation energies to reach TiO₂. Employed as photocatalysts in hydrogen evolution under visible light, amorphous TiO₂ hardly exhibits the catalytic activity due to high defect density, whereas Ag/TiO₂-3 represents a remarkably high catalytic efficiency. The enhancement mechanism of the reaction rate is proposed by the analysis of the compositional, structural, and optical properties from a series of Ag/TiO₂ composites.