The subsurface Pt-promoted TiO_2−x overlayer enhances succinonitrile production in the photocatalytic C–C coupling of acetonitrile

Photocatalytic coupling of monofunctional molecules offers an atom-efficient route for the synthesis of value-added bifunctional organic compounds, yet its efficiency is significantly limited by the reverse reaction of radicals. Our density functional theory (DFT) calculations have indicated that a unique structure of partially exposed Pt encapsulated by a titanium oxide (TiO₂) overlayer could intrinsically facilitate the desorption and suppress re-adsorption of reactive radicals, hence impeding the reverse reaction in the photocatalytic acetonitrile coupling reaction. A TiO_2−x/Pt inverse heterostructure has then been developed via strong metal–support interaction (SMSI) with tunable TiO_2−x coverage. Among the catalysts, an optimal partially encapsulated TiO_2−x/Pt catalyst achieves a marked formation rate of succinonitrile of 8.41 mmol·g_cat⁻¹· h⁻¹ from acetonitrile, reaching a 67.3% radical-to-product efficiency and a 5.6% apparent quantum yield, representing 3-fold enhancements over a conventional Pt-supported TiO₂ catalyst, over 1.9-fold higher than bare Pt/TiO₂ or fully encapsulated counterparts, respectively. Kinetic investigations demonstrate that the suppression of radical–proton recombination plays a more dominant role in the overall coupling performance compared to the radical initiation. This work underscores the critical role of tailored catalysts by coating with oxide domains to mitigate reverse reactions and establishes an effective strategy for advancing the efficiency in photocatalytic coupling.