Palladium Encapsulated by an Oxygen‐Saturated TiO2 Overlayer for Low‐Temperature SO2‐Tolerant Catalysis during CO Oxidation

• Published in: Angewandte Chemie International Edition 2023-12, Vol.62 (49), p.e202310191-n/a
• Main Authors: Chen, Jingkun, Su, Yuetan, Meng, Qingjie, Qian, Hehe, Shi, Le, Darr, Jawwad A., Wu, Zhongbiao, Weng, Xiaole
• Format: Article
• Language: English
• Subjects: Bonding strength; Carbon monoxide; Catalysis; Catalysts; Chemical synthesis; CO Oxidation; Density functional theory; Life span; Low temperature; Metals; Non-Metal Active Site; Oxidation; Oxidation resistance; Oxide-Metal Interaction; Oxygen; Oxygen atoms; Palladium; Poisoning; Poisoning (reaction inhibition); Stability; Sulfur; Sulfur dioxide; Sulfur Tolerance; Temperature tolerance; Titanium dioxide; Working conditions
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202310191

The development of oxidation catalysts that are resistant to sulfur poisoning is crucial for extending the lifespan of catalysts in real‐working conditions. Herein, we describe the design and synthesis of oxide‐metal interaction (OMI) catalyst under oxidative atmospheres. By using organic coated TiO2, an oxide/metal inverse catalyst with non‐classical oxygen‐saturated TiO2 overlayers were obtained at relatively low temperature. These catalysts were found to incorporate ultra‐small Pd metal and support particles with exceptional reactivity and stability for CO oxidation (under 21 vol % O2 and 10 vol % H2O). In particular, the core (Pd)‐shell (TiO2) structured OMI catalyst exhibited excellent resistance to SO2 poisoning, yielding robust CO oxidation performance at 120 °C for 240 h (at 100 ppm SO2 and 10 vol % H2O). The stability of this new OMI catalyst was explained through density functional theory (DFT) calculations that interfacial oxygen atoms at Pd−O−Ti sites (of oxygen‐saturated overlayers) serve as non‐metal active sites for low‐temperature CO oxidation, and change the SO2 adsorption from metal(d)‐to‐SO2(π*) back‐bonding to much weaker σ(Ti−S) bonding. An oxygen‐saturated TiO2 overlayer was constructed on Pd nanoparticles in air at only 400 °C. The resulting catalyst with non‐metal active sites exhibited an exceptional resistance to poisoning by SO2 and H2O, yielding robust CO oxidation performance under 100 ppm SO2 and 10 vol % H2O at temperatures as low as 120 °C for at least 240 h.