Tiny Species with Big Impact: High Activity of Cu Single Atoms on CeO2–TiO2 Deciphered by Operando Spectroscopy
- Jawaher MosratiJawaher MosratiLeibniz-Institut für Katalyse, Albert-Einstein-Str. 29A, 18059 Rostock, GermanyLaboratoire de chimie des matériaux et catalyse, Département de chimie, Faculté des sciences de Tunis, Université de Tunis el Manar, Tunis 1092, TunisieMore by Jawaher Mosrati,
- Ali M. Abdel-MageedAli M. Abdel-MageedInstitute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, D-89081 Ulm, GermanyDepartment of Chemistry, Faculty of Science, Cairo University, Giza 12613, EgyptMore by Ali M. Abdel-Mageed,
- Thanh Huyen VuongThanh Huyen VuongLeibniz-Institut für Katalyse, Albert-Einstein-Str. 29A, 18059 Rostock, GermanyMore by Thanh Huyen Vuong,
- Reni GraukeReni GraukeLeibniz-Institut für Katalyse, Albert-Einstein-Str. 29A, 18059 Rostock, GermanyMore by Reni Grauke,
- Stephan Bartling ,
- Nils RockstrohNils RockstrohLeibniz-Institut für Katalyse, Albert-Einstein-Str. 29A, 18059 Rostock, GermanyMore by Nils Rockstroh,
- Hanan AtiaHanan AtiaLeibniz-Institut für Katalyse, Albert-Einstein-Str. 29A, 18059 Rostock, GermanyMore by Hanan Atia,
- Udo ArmbrusterUdo ArmbrusterLeibniz-Institut für Katalyse, Albert-Einstein-Str. 29A, 18059 Rostock, GermanyMore by Udo Armbruster,
- Sebastian Wohlrab ,
- Jabor Rabeah* , and
- Angelika Brückner*
Cu single-atom catalysts (SACs) supported on CeO2–TiO2 were prepared by a sol–gel method and tested for CO oxidation between 120 and 350 °C. Operando and in situ spectroscopic methods including diffuse reflectance infrared Fourier transform (DRIFT), electron paramagnetic resonance (EPR), and near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) combined with other basic characterizations were applied to identify active sites and to derive reliable structure–reactivity relationships. Rising the Cu content from 0.06 to 0.86 wt % resulted in a significant decrease of the Cu-mass normalized CO2 formation rate from 690 to 310 μmolCO2·gCu–1·s–1 at 250 °C, which was attributed to the formation of the less active CuOx species. The catalysts showed high stability during time on stream for more than 1000 min with negligible agglomeration of Cu single sites. Spectroscopic results revealed that active sites are single Cu ions on the surface of highly dispersed ceria particles, shuttling between −Cu2+–O–Ce4+– and −Cu+–□–Ce3+– by supplying active oxygen for oxidation of CO to CO2. The highest concentrations of Cu single sites and O vacancies associated with Ce3+ species correlated with the highest CO oxidation activity.
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