Cu/CeO2 catalysts are highly active for the low-temperature water–gas shift—a core reaction in syngas chemistry for tuning the H2/CO/CO2 proportions in feed streams—but the direct identification and quantitative description of the active sites remain challenging. Here we report that the active copper clusters consist of a bottom layer of mainly Cu+ atoms bonded on the oxygen vacancies (Ov) of ceria, in a form of Cu+–Ov–Ce3+, and a top layer of Cu0 atoms coordinated with the underlying Cu+ atoms. This atomic structure model is based on directly observing copper clusters dispersed on ceria by a combination of scanning transmission electron microscopy and electron energy loss spectroscopy, in situ probing of the interfacial copper–ceria bonding environment by infrared spectroscopy and rationalization by density functional theory calculations. These results, together with reaction kinetics, reveal that the reaction occurs at the copper–ceria interfacial perimeter via a site cooperation mechanism: the Cu+ site chemically adsorbs CO whereas the neighbouring Ov–Ce3+ site dissociatively activates H2O.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
Li, Y., Fu, Q. & Flytzani-Stephanopoulos, M. Low-temperature water–gas shift reaction over Cu- and Ni-loaded cerium oxide catalysts. Appl. Catal. B 27, 179–191 (2000).
Wang, X. et al. In situ studies of the active sites for the water gas shift reaction over Cu−CeO2 catalysts: complex interaction between metallic copper and oxygen vacancies of ceria. J. Phys. Chem. B 110, 428–434 (2006).
Gawade, P., Mirkelamoglu, B. & Ozkan, U. S. The role of support morphology and impregnation medium on the water gas shift activity of ceria-supported copper catalysts. J. Phys. Chem. C 114, 18173–18181 (2010).
Si, R. et al. Structure sensitivity of the low-temperature water–gas shift reaction on Cu–CeO2 catalysts. Catal. Today 180, 68–80 (2012).
Yao, S. et al. Morphological effects of the nanostructured ceria support on the activity and stability of CuO/CeO2 catalysts for the water–gas shift reaction. Phys. Chem. Chem. Phys. 16, 17183–17195 (2014).
Ren, Z., Peng, F., Li, J., Liang, X. & Chen, B. Morphology-dependent properties of Cu/CeO2 catalysts for the water–gas shift reaction. Catalysts 7, 48–60 (2017).
Chen, C. et al. Cu/CeO2 catalyst for water–gas shift reaction: effect of CeO2 pretreatment. ChemPhysChem 19, 1448–1455 (2018).
Shen, W., Ichihashi, Y. & Matsumura, Y. Low-temperature methanol synthesis from carbon monoxide and hydrogen over ceria supported copper catalyst. Appl. Catal. A 282, 221–226 (2005).
Yang, R. et al. Performance of Cu-based catalysts in low-temperature methanol synthesis. Adv. Mater. Res. 1004–1005, 1623–1626 (2014).
Graciani, J. et al. Highly active copper–ceria and copper–ceria–titania catalysts for methanol synthesis from CO2. Science 345, 546–551 (2014).
Rodriguez, J. A. et al. Hydrogenation of CO2 to methanol: importance of metal–oxide and metal–carbide interfaces in the activation of CO2. ACS Catal. 5, 6696–6706 (2015).
Ouyang, B., Tan, W. & Li, B. Morphology effect of nanostructure ceria on the Cu/CeO2 catalysts for synthesis of methanol from CO2 hydrogenation. Catal. Commun. 95, 36–39 (2017).
van de Water, L. G. A., Wilkinson, S. K., Smith, R. A. P. & Watson, M. J. Understanding methanol synthesis from CO/H2 feeds over Cu/CeO2 catalysts. J. Catal. 364, 57–68 (2018).
Konsolakis, M. The role of copper–ceria interactions in catalysis science: recent theoretical and experimental advances. Appl. Catal. B 198, 49–66 (2016).
Trovarelli, A. & Llorca, J. Ceria catalysts at nanoscale: how do crystal shapes shape catalysis? ACS Catal. 7, 4716–4735 (2017).
Rodriguez, J. A., Grinter, D. C., Liu, Z., Palomino, R. M. & Senanayake, S. D. Ceria-based model catalysts: fundamental studies on the importance of the metal–ceria interface in CO oxidation, the water–gas shift, CO2 hydrogenation, and methane and alcohol reforming. Chem. Soc. Rev. 46, 1824–1841 (2017).
Mudiyanselage, K. et al. Importance of the metal–oxide interface in catalysis: in situ studies of the water–gas shift reaction by ambient-pressure X-ray photoelectron spectroscopy. Angew. Chem. Int. Ed. 52, 5101–5105 (2013).
Senanayake, S. D., Stacchiola, D. & Rodriguez, J. A. Unique properties of ceria nanoparticles supported on metals: novel inverse ceria/copper catalysts for CO oxidation and the water–gas shift reaction. Acc. Chem. Res. 46, 1702–1711 (2013).
Szabová, L., Camellone, M. F., Huang, M., Matolín, V. & Fabris, S. Thermodynamic, electronic and structural properties of Cu/CeO2 surfaces and interfaces from first-principles DFT + U calculations. J. Chem. Phys. 133, 234705 (2010).
Yang, Z., Xie, L., Ma, D. & Wang, G. Origin of the high activity of the ceria-supported copper catalyst for H2O dissociation. J. Phys. Chem. C 115, 6730–6740 (2011).
James, T. E., Hemmingson, S. L., Ito, T. & Campbell, C. T. Energetics of Cu adsorption and adhesion onto reduced CeO2(111) surfaces by calorimetry. J. Phys. Chem. C 119, 17209–17217 (2015).
James, T. E., Hemmingson, S. L. & Campbell, C. T. Energy of supported metal catalysts: from single atoms to large metal nanoparticles. ACS Catal. 5, 5673–5678 (2015).
Chutia, A. et al. The adsorption of Cu on the CeO2(110) surface. Phys. Chem. Chem. Phys. 19, 27191–27203 (2017).
Si, R. & Flytzani-Stephanopoulos, M. Shape and crystal-plane effects of nanoscale ceria on the activity of Au–CeO2 catalysts for the water–gas shift reaction. Angew. Chem. Int. Ed. 47, 2884–2887 (2008).
Farmer, J. A. & Campbell, C. T. Ceria maintains smaller metal catalyst particles by strong metal-support bonding. Science 329, 933–936 (2010).
Yamada, Y. et al. Nanocrystal bilayer for tandem catalysis. Nat. Chem. 3, 372–376 (2011).
Yoshida, H. et al. Visualizing gas molecules interacting with supported nanoparticulate catalysts at reaction conditions. Science 335, 317–319 (2012).
Cargnello, M. et al. Control of metal nanocrystal size reveals metal–support interface role for ceria catalysts. Science 341, 771–773 (2013).
Lin, Y. et al. Adhesion and atomic structures of gold on ceria nanostructures: the role of surface structure and oxidation state of ceria supports. Nano Lett. 15, 5375–5381 (2015).
Gänzler, A. M. et al. Tuning the Pt/CeO2 interface by in situ variation of the Pt particle size. ACS Catal. 8, 4800–4811 (2018).
Chen, A., Zhou, Y., Ta, N., Li, Y. & Shen, W. Redox properties and catalytic performance of ceria–zirconia nanorods. Catal. Sci. Technol. 5, 4184–4192 (2015).
Tang, X. et al. CuO/CeO2catalysts: redox features and catalytic behaviors. Appl. Catal. A 288, 116–125 (2005).
Wang, W. et al. Crystal plane effect of ceria on supported copper oxide cluster catalyst for CO oxidation: importance of metal–support Interaction. ACS Catal. 7, 1313–1329 (2017).
Wu, L. et al. Oxidation state and lattice expansion of CeO2–x nanoparticles as a function of particle size. Phys. Rev. B 69, 125415 (2004).
Keast, V. J., Scott, A. J., Brydson, R., Williams, D. B. & Bruley, J. Electron energy-loss near-edge structure—a tool for the investigation of electronic structure on the nanometre scale. J. Microsc. 203, 135–175 (2001).
Wagner, J. B. et al. In situ electron energy loss spectroscopy studies of gas-dependent metal–support interactions in Cu/ZnO catalysts. J. Phys. Chem. B 107, 7753–7758 (2003).
Wang, Y. & Wöll, C. IR spectroscopic investigations of chemical and photochemical reactions on metal oxides: bridging the materials gap. Chem. Soc. Rev. 46, 1875–1932 (2017).
Yang, C. et al. Chemical activity of oxygen vacancies on ceria: a combined experimental and theoretical study on CeO2(111). Phys. Chem. Chem. Phys. 16, 24165–24168 (2014).
Yang, C. et al. Surface faceting and reconstruction of ceria nanoparticles. Angew. Chem. Int. Ed. 56, 375–379 (2017).
Cox, D. F. & Schulz, K. H. Interaction of CO with Cu+ cations: CO adsorption on Cu2O(100). Surf. Sci. 249, 138–148 (1991).
Martı́nez-Arias, A., Fernández-Garcı́a, M., Soria, J. & Conesa, J. C. Spectroscopic study of a Cu/CeO2 catalyst subjected to redox treatments in carbon monoxide and oxygen. J. Catal. 182, 367–377 (1999).
Vollmer, S., Witte, G. & Wöll, C. Determination of site specific adsorption energies of CO on copper. Catal. Lett. 77, 97–101 (2001).
Chen, S. et al. Anchoring high-concentration oxygen vacancies at interfaces of CeO2–x/Cu toward enhanced activity for preferential CO oxidation. ACS Appl. Mater. Interfaces 7, 22999–23007 (2015).
Fabris, S., Vicario, G., Balducci, G., de Gironcoli, S. & Baroni, S. Electronic and atomistic structures of clean and reduced ceria surfaces. J. Phys. Chem. B 109, 22860–22867 (2005).
Lykhach, Y. et al. Counting electrons on supported nanoparticles. Nat. Mater. 15, 284–288 (2016).
Branda, M. M., Hernández, N. C., Sanz, J. F. & Illas, F. Density functional theory study of the interaction of Cu, Ag, and Au atoms with the regular CeO2(111) surface. J. Phys. Chem. C 114, 1934–1941 (2010).
Figueroba, A., Kovács, G., Bruix, A. & Neyman, K. M. Towards stable single-atom catalysts: strong binding of atomically dispersed transition metals on the surface of nanostructured ceria. Catal. Sci. Technol. 6, 6806–6813 (2016).
Li, L. et al. Water–gas shift reaction over CuO/CeO2 catalysts: effect of the thermal stability and oxygen vacancies of CeO2 supports previously prepared by different methods. Catal. Lett. 130, 532–540 (2009).
López. Cámara, A., Chansai, S., Hardacre, C. & Martínez-Arias, A. The water–gas shift reaction over CeO2/CuO: operando SSITKA–DRIFTS–mass spectrometry study of low temperature mechanism. Int. J. Hydrogen Energy 39, 4095–4101 (2014).
Caldas, P. C. P., Gallo, J. M. R., Lopez-Castillo, A., Zanchet, D. & Bueno, J. M. C. The structure of the Cu–CuO sites determines the catalytic activity of Cu nanoparticles. ACS Catal. 7, 2419–2424 (2017).
This work is supported by the National Natural Science Foundation of China (grant numbers 91645107, 21533009, 21621063 and 21761132031), the Deutsche Forschungsgemeinschaft (WA 2535/2-1), the ‘Science and Technology of Nanosystems’ Programme (grant no. 432202) of Germany and the EU-H2020 research and innovation programme (grant no. 654360 NFFA-Europe). X.Y. and C.Y. thank PhD fellowships sponsored by the China Scholarship Council.
The authors declare no competing interests.
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Chen, A., Yu, X., Zhou, Y. et al. Structure of the catalytically active copper–ceria interfacial perimeter. Nat Catal 2, 334–341 (2019). https://doi.org/10.1038/s41929-019-0226-6
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