Pt/TiO2 catalysts: Unveiling interfacial activity via metal nanocrystal size control in benzene combustion

The elucidation of active sites in Pt-based catalysts for benzene combustion has been a long-standing challenge, hindering the rational design of such catalysts. We have successfully pinpointed the active sites to the perimeters of Pt nanoparticles, deliberately excluding corner atoms. This achievement stems from a comprehensive approach, encompassing controlled synthesis of Pt nanocrystal size and morphology, advanced spectroscopic characterization, and detailed geometrical model analysis. We synthesized well-defined truncated hexahedral Pt nanoparticles with diameters (d) ranging from 2.2 to 6.6 nm. Notably, the turnover frequency (TOF) of our Pt/TiO 2 catalyst correlates inversely with the nanoparticle diameter, following a d -1.09±0.11 trend. This correlation matches the model-predicted perimeter-to-diameter ratio (excluding corners) with a d -1.01±0.09 exponent, confirming the location of the active sites. Further support comes from X-ray photoelectron spectroscopy and experiments using different support materials, which underscore the high activity at the Pt/TiO 2 interface. A crucial H 2 treatment step encapsulating the Pt nanoparticles by TiO x excludes both surface areas and corners as contributing active sites. The 0.7 % Pt/TiO 2 catalyst also demonstrated remarkable stability under testing conditions. In situ FTIR analysis provided insight into the stepwise mechanism of benzene combustion, revealing intermediate species and their transformation pathways. By finely tuning the geometry of Pt nanoparticles and correlating TOF with specific surface sites, our research highlights the perimeters of Pt atoms as the prime active sites for benzene combustion. These results contribute significantly to the field, offering a strategic approach to designing efficient catalysts for VOC elimination, with implications for both environmental protection and the advancement of catalytic science.