CO Oxidation on Metal Oxide Supported Single Pt atoms: The Role of the Support

Supported metal single atoms have demonstrated excellent catalytic performance for many chemical transformations. The effects of support on the catalytic performance of supported single metal atoms, however, have not been clearly elucidated. We carried out a systematic investigation of the effects of supports on CO oxidation by single Pt (Pt₁) atoms dispersed on different metal oxides: highly reducible Fe₂O₃, reducible ZnO, and irreducible γ-Al₂O₃. It was found that Pt₁ atoms on three metal oxides are active for CO oxidation, and the chemical properties of supports determine the catalytic performance of Pt₁ single-atom catalysts (SACs). Both the presence of −OH groups on support surfaces and the addition of H₂O significantly modify CO oxidation on three SACs and reduce the effects of supports on their catalytic performances. We conclude that the interaction between single metal atoms and support as well as surface properties of supports control the catalytic behavior of SACs

Low-Temperature Methane Combustion over Pd/H-ZSM-5: Active Pd Sites with Specific Electronic Properties Modulated by Acidic Sites of H‑ZSM‑5

Pd/H-ZSM-5 catalysts could completely catalyze CH₄ to CO₂ at as low as 320 °C, while there is no detectable catalytic activity for pure H-ZSM-5 at 320 °C and only a conversion of 40% could be obtained at 500 °C over pure H-ZSM-5. Both the theoretical and experimental results prove that surface acidic sites could facilitate the formation of active metal species as the anchoring sites, which could further modify the electronic and coordination structure of metal species. PdO_<i>x</i> interacting with the surface Brönsted acid sites of H-ZSM-5 could exhibit Lewis acidity and lower oxidation states, as proven by the XPS, XPS valence band, CO-DRIFTS, pyridine FT-IR, and NH₃-TPD data. Density functional theory calculations suggest PdO_<i>x</i> groups to be the active sites for methane combustion, in the form of [AlO₂]­Pd­(OH)-ZSM-5. The stronger Lewis acidity of coordinatively unsaturated Pd and the stronger basicity of oxygen from anchored PdO_<i>x</i> species are two key characteristics of the active sites ([AlO₂]­Pd­(OH)-ZSM-5) for methane combustion. As a result, the PdO_<i>x</i> species anchored by Brønsted acid sites of H-ZSM-5 exhibit high performance for catalytic combustion of CH₄ over Pd/H-ZSM-5 catalysts

Revealing the Size Effect of Ceria Nanocube-Supported Platinum Nanoparticles in Complete Propane Oxidation

The elimination of propane is one of the key tasks in reducing volatile organic compounds (VOCs) and automotive exhaust emissions. The platinum nanoparticle (NP) is a promising catalyst for propane oxidation, while the study of its structural characteristics and functionality remains in its infancy. In this work, we synthesized the nanocubes CeO2 with a well-defined (100) facet supporting Pt NPs with various sizes, from 1.3 to 7 nm, and systematically investigated the effect of the Pt size on complete propane oxidation efficiency. In particular, CeO2(100) supported Pt NPs smaller than 4 nm promote the formation of positively charged Pt sites, which hinder the adsorption and activation of propane and reduce the intrinsic activity for propane oxidation. Consequently, within this size range, the catalytic performance is primarily influenced by the electronic state of the Pt species, with metallic Pt being identified as the active site for the reaction. Conversely, as the particle size exceeds 4 nm, metallic Pt particles become dominant and the geometric structure starts to influence the activity as well. Such entanglement of electronic and geometric factors gives rise to a volcano relationship between reaction rates and Pt particle sizes ranging from 1.3 to 7 nm, while an increased correlation can be observed between the turnover frequencies and the particle sizes in this range. This knowledge can guide the synthesis of highly active catalysts, enabling the efficient oxidation of VOCs with reduced precious metal loadings