Pt Molecularly Defined Precursors to Tune Particle Size and Speciation: Impact on the Reverse Water Gas Shift Reaction

Platinum-based catalysts have been largely explored for CO2 valorization by the reverse water gas shift (RWGS) reaction, especially the Pt/TiO2 system. Understanding the distinct roles of various Pt species and the metal–support interaction, as well as finding ways to tailor them, is crucial for developing and optimizing more active systems. Herein, we employed molecularly defined Pt2+ precursors based on salen ligand for easy Pt speciation according to the activation protocol. Salen-derived ligands are easily accessible coordination compounds that can be designed and combined with various metals, serving as versatile alternatives to create a broad library of metallic precursors. Pyrolysis, oxidizing, or reducing thermal pretreatments were used to decompose the coordination complexes impregnated on TiO2, impacting the Pt species formed, their local environment, electronic properties, and interaction with the support. We showed that at low temperatures (below 300 °C), metallic Pt nanoparticles had the highest activities; however, once exposed to harsher reactional conditions (>400 °C), they deactivated. On the other hand, an oxidative pretreatment induced the growth of mobile platinum clusters that, under a harsher reducing RWGS reactional atmosphere, redispersed into single atoms, being the dominant active site and presenting high activity and stability.