Controlling Activity of Heterogeneous Cu Single‐Atom Catalysts by Fine‐Tuning the Redox Properties of CeO2‐TiO2 Supports

• Published in: ChemCatChem 2023-04, Vol.15 (8), p.n/a
• Main Authors: Abdel‐Mageed, Ali M., Cisneros, Sebastian, Mosrati, Jawaher, Atia, Hanan, Vuong, Thanh Huyen, Rockstroh, Nils, Wohlrab, Sebastian, Brückner, Angelika, Rabeah, Jabor
• Format: Article
• Language: English
• Subjects: Carbon monoxide; Catalytic activity; Cerium oxides; CO oxidation; Cu/CeO2-TiO2; heterogeneous single-atom catalyst; Industrial applications; operando spectroscopy; Oxidation; redox properties; Single atom catalysts; Titanium; Titanium dioxide
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202201669

Understanding and enhancing the activity of heterogeneous single‐atom catalysts (SACs) are indispensable aspects to use them in industrial applications. Among these, low‐temperature CO oxidation is considered as a model reaction for testing a wide‐range of oxidation catalysts, and as an essential process for the exhaust aftertreatment in modern combustion engines. This study demonstrates that the activity of heterogeneous Cu/CeO2−TiO2 SAC catalysts can be fine‐tuned by controlling the Ce/Ti ratio in CeO2−TiO2 supports, with the highest catalytic activity achieved for a Ce/Ti molar ratio of 0.18. Based on DRIFT, EEL, and EPR spectroscopies, together with high‐resolution electron microscopy and H2‐TPR measurements, it is inferred that the optimized Ce/Ti ratio correlates with i) highest dispersion of separate CeO2 particles on TiO2 surface, ii) more facile reduction of Ce4+ to Ce3+, and iii) enhanced formation of −Cu2+−O−Ce4+−⇆−Cu+−□−Ce3+− redox shuttles, which play a dual role for CO adsorption and O2‐activation. These results extend the understanding of heterogeneous metal single‐atom catalysts and constitute a robust approach for the rational control of their catalytic performance in technically relevant applications. Optimizing the activity of heterogeneous single‐atom catalysts (SACs) is indispensable to use them in industrial applications. This study demonstrates that the activity of heterogeneous Cu/CeO2−TiO2 SAC catalysts can be fine‐tuned by controlling the Ce/Ti ratio in CeO2−TiO2 supports. A multitude of characterizations including operando / in situ spectroscopic methods reveal a magic ratio of Ce/Ti around which catalytic activity culminates.