Classical strong metal-support interactions between gold nanoparticles and titanium dioxide

Supported metal catalysts play a central role in the modern chemical industry but often exhibit poor on-stream stability. The strong metal-support interaction (SMSI) offers a route to control the structural properties of supported metals and, hence, their reactivity and stability. Conventional wisdom holds that supported Au cannot manifest a classical SMSI, which is characterized by reversible metal encapsulation by the support upon high-temperature redox treatments. We demonstrate a classical SMSI for Au/TiO₂, evidenced by suppression of CO adsorption, electron transfer from TiO₂ to Au nanoparticles, and gold encapsulation by a TiO overlayer following high-temperature reduction (reversed by subsequent oxidation), akin to that observed for titania-supported platinum group metals. In the SMSI state, Au/TiO₂ exhibits markedly improved stability toward CO oxidation. The SMSI extends to Au supported over other reducible oxides (Fe₃O₄ and CeO₂) and other group IB metals (Cu and Ag) over titania. This discovery highlights the general nature of the classical SMSI and unlocks the development of thermochemically stable IB metal catalysts.