CO₂ Hydrogenation-Induced Size-Dependent Strong Metal-Support Interactions in Platinum/Titanium Dioxide Catalysts

The catalytic performance of heterogeneous catalysts can be modulated by tailoring the size and structure of supported transition metals, which typically serve as active sites. In this study, a strategy is proposed to design CO₂ hydrogenation-induced size-dependent strong metal-support interactions (SMSI) between platinum (Pt) and rutile by simultaneously regulating the in situ phase transformation of TiO₂ and the sintering of Pt single atoms. It is demonstrated that the size of Pt nanoparticles supported on rutile governs the strength of electronic metal-support interactions (EMSI), the nature of SMSI, and the reactivity in the reverse water-gas shift (RWGS) reaction. In situ diffuse reflectance infrared Fourier transform spectroscopy of CO chemisorption and electron energy loss spectroscopy reveal that larger and smaller Pt nanoparticles are encapsulated by TiO_2-x overlayers in a discontinuous and continuous manner, respectively. Larger Pt nanoparticles (≈7 nm) exhibiting mild-EMSI on rutile show 1.7 folds higher CO₂ conversion than smaller ones (≈4 nm) with ultra-EMSI during the RWGS reaction at 800 °C. Combined experimental results and density functional theory calculations indicate that mild-EMSI, associated with Ti-O-Pt interfacial structure, promotes d-electrons delocalization on the Pt surface, weakening adsorbate binding energies and lowering the activation barrier for the RWGS reaction.