Hydrothermal Embedding of Pd Single Atoms Into SnO2 for Efficient CO Oxidation.

This work employs a hydrothermal embedding strategy to fabricate a highly efficient and stable Pd/SnO2 catalyst for CO oxidation. With only 0.15 wt.% Pd, the hydrothermally treated catalyst (Pd/SnO2-H) exhibits a reaction rate three times that of the fresh counterpart (Pd/SnO2-F). Combined experimental and theoretical evidence reveals that hydrothermal treatment redistributes Pd species and partially incorporates Pd atoms into the SnO2 lattice, generating single-atom Pd sites (Pd1). These lattice-incorporated Pd1 sites strengthen the Pd-SnO2 interaction, which weakens the Pd─O bond, thereby promoting the formation of oxygen vacancies and, more importantly, facilitating the subsequent rate-determining O2 activation step. This enables a low-barrier Mars-van Krevelen pathway, in contrast to the higher-energy Langmuir-Hinshelwood route operating on PdO clusters in Pd/SnO2-F, thereby explaining the high intrinsic activity of Pd/SnO2-H. Furthermore, Pd lattice doping modulates the d-electron distribution of Pd and weakens CO adsorption, effectively alleviating the CO poisoning typically observed on conventional Pd nanoparticles. Together, these results establish a new design principle for high-performance single-atom catalysts, demonstrating that lattice‑embedding of the active metal into a reducible oxide support can simultaneously enhance redox kinetics and suppress poisoning.