Metal–Support Interactions in Pt-WO3 Heterostructures: Role of WO3 Polymorphism

Ionic exchange under soft conditions yields nanoplatelets of tungsten bronzes with an original crystal structure doped with cobalt, copper, platinum, and cesium cations (h′-M x WO3). The optimal orientation of the tunnel-based crystal structure, perpendicular to the basal plane of the nanoplatelets, facilitates cation exchange so that the dopant cations are located inside the (WO6)6 channels, as evidenced by scanning transmission electron microscopy and electron energy loss spectroscopy. This synthetic pathway allows one to obtain not only doped materials but also metallic nanoparticles supported over h′-WO3 nanoplatelets after reduction. Consequently, this approach opens a route to target new hexagonal bronze compositions. We have used this approach to design Pt nanoparticles supported over the two known hexagonal WO3 polymorphs: h′-WO3 and h-WO3. By using the catalysis of CO oxidation as a probe, we highlight differences in the metal–support interaction on these Pt-WO3 heterostructures, especially higher electron transfer from the newly discovered h′-WO3 framework.