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Chemical gradients in automotive Cu-SSZ-13 catalysts for NOx removal revealed by operando X-ray spectrotomography


Nitrogen oxide (NOx) emissions are a major source of pollution, demanding ever-improving performance from catalytic after-treatment systems. However, catalyst development is often hindered by limited understanding of the catalyst at work, exacerbated by widespread use of model catalysts rather than technical catalysts, and by global rather than spatially resolved characterization tools. Here we combine operando X-ray absorption spectroscopy with microtomography to perform three-dimensional chemical imaging of the chemical state of copper species in a Cu-SSZ-13 washcoated monolith catalyst during NOx reduction. Gradients in copper oxidation state and coordination environment, resulting from an interplay of NOx reduction with adsorption–desorption of NH3 and mass transport phenomena, were revealed at micrometre spatial resolution while simultaneously determining catalytic performance. Crucially, direct three-dimensional visualization of complex reactions on non-model catalysts is feasible only by the use of operando X-ray spectrotomography, which can improve our understanding of structure–activity relationships, including the observation of mass and heat transport effects.

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Fig. 1: Operando spectrotomography of a Cu-SSZ-13 catalyst at work.
Fig. 2: 3D view of the chemical gradient in a Cu-SSZ-13 washcoat.
Fig. 3: Revealing the chemical state of Cu in a Cu-SSZ-13 washcoat.

Data availability

Raw data were generated at the Swiss Light Source of the Paul Scherrer Institut (Switzerland). The collected and cleaned imaging data acquired before tomographic reconstruction that support the findings of this study are stored in KITopen, the central repository of the Karlsruhe Institute of Technology, and are freely available with the following DOIs: 200 °C dataset,; 300 °C dataset,; 350 °C dataset,; 400 °C dataset,; NH3 reference dataset,; NO reference dataset, Additional data, including reconstructed and treated spectrotomography datasets, are available from the authors upon reasonable request. Source Data for Figs. 13 are provided with the paper.


  1. 1.

    Beale, A. M., Gao, F., Lezcano-Gonzalez, I., Peden, C. H. F. & Szanyi, J. Recent advances in automotive catalysis for NOx emission control by small-pore microporous materials. Chem. Soc. Rev. 44, 7371–7405 (2015).

    CAS  PubMed  Google Scholar 

  2. 2.

    Borfecchia, E. et al. Cu-CHA—a model system for applied selective redox catalysis. Chem. Soc. Rev. 47, 8097–8133 (2018).

    CAS  PubMed  Google Scholar 

  3. 3.

    Lomachenko, K. A. et al. The Cu-CHA deNOx catalyst in action: temperature-dependent NH3-assisted selective catalytic reduction monitored by operando XAS and XES. J. Am. Chem. Soc. 138, 12025–12028 (2016).

    CAS  PubMed  Google Scholar 

  4. 4.

    Janssens, T. V. W. et al. A consistent reaction scheme for the selective catalytic reduction of nitrogen oxides with ammonia. ACS Catal. 5, 2832–2845 (2015).

    CAS  Google Scholar 

  5. 5.

    Bates, S. A. et al. Identification of the active Cu site in standard selective catalytic reduction with ammonia on Cu-SSZ-13. J. Catal. 312, 87–97 (2014).

    CAS  Google Scholar 

  6. 6.

    Günter, T. et al. Structural snapshots of the SCR reaction mechanism on Cu-SSZ-13. Chem. Commun. 51, 9227–9230 (2015).

    Google Scholar 

  7. 7.

    Günter, T. et al. The SCR of NOx with NH3 examined by novel X-ray emission and X-ray absorption methods. Top. Catal. 59, 866–874 (2016).

    Google Scholar 

  8. 8.

    Paolucci, C. et al. Dynamic multinuclear sites formed by mobilized copper ions in NOx selective catalytic reduction. Science 357, 898–903 (2017).

    CAS  PubMed  Google Scholar 

  9. 9.

    Fahami, A. R. et al. The dynamic nature of Cu sites in Cu-SSZ-13 and the origin of the seagull NOx conversion profile during NH3-SCR. React. Chem. Eng. 4, 1000–1018 (2019).

    CAS  Google Scholar 

  10. 10.

    Kerkeni, B. et al. Copper coordination to water and ammonia in CuII-exchanged SSZ-13: atomistic insights from DFT calculations and in situ XAS experiments. J. Phys. Chem. C 122, 16741–16755 (2018).

    CAS  Google Scholar 

  11. 11.

    Auvray, X. et al. Local ammonia storage and ammonia inhibition in a monolithic copper-beta zeolite SCR catalyst. Appl. Catal. B 126, 144–152 (2012).

    CAS  Google Scholar 

  12. 12.

    Marberger, A. et al. Time-resolved copper speciation during selective catalytic reduction of NO on Cu-SSZ-13. Nat. Catal. 1, 221–227 (2018).

    CAS  Google Scholar 

  13. 13.

    Greenaway, A. G. et al. Detection of key transient Cu intermediates in SSZ-13 during NH3-SCR deNOx by modulation excitation IR spectroscopy. Chem. Sci. 11, 447–455 (2020).

    CAS  PubMed  Google Scholar 

  14. 14.

    Clark, A. H. et al. Selective catalytic reduction of NO with NH3 on Cu‐SSZ‐13: deciphering the low- and high‐temperature rate‐limiting steps by transient XAS experiments. ChemCatChem 12, 1429–1435 (2020).

    CAS  Google Scholar 

  15. 15.

    Grunwaldt, J.-D., Wagner, J. B. & Dunin-Borkowski, R. E. Imaging catalysts at work: a hierarchical approach from the macro- to the meso- and nano-scale. ChemCatChem 5, 62–80 (2013).

    CAS  Google Scholar 

  16. 16.

    Gänzler, A. M. et al. Unravelling the different reaction pathways for low temperature CO oxidation on Pt/CeO2 and Pt/Al2O3 by spatially resolved structure–activity correlations. J. Phys. Chem. Lett. 10, 7698–7705 (2019).

    PubMed  Google Scholar 

  17. 17.

    Andrews, J. C. & Weckhuysen, B. M. Hard X‐ray spectroscopic nano‐imaging of hierarchical functional materials at work. ChemPhysChem 14, 3655–3666 (2013).

    CAS  PubMed  Google Scholar 

  18. 18.

    Goguet, A., Stewart, C., Touitou, J. & Morgan, K. in Spatially Resolved Operando Measurements in Heterogeneous Catalytic Reactors Vol. 50 (eds Dixon, A. G. & Deutschmann, O.) 131–160 (Elsevier, 2017).

  19. 19.

    Dong, Y., Korup, O., Gerdts, J., Roldán Cuenya, B. & Horn, R. Microtomography-based CFD modeling of a fixed-bed reactor with an open-cell foam monolith and experimental verification by reactor profile measurements. Chem. Eng. J. 353, 176–188 (2018).

    CAS  Google Scholar 

  20. 20.

    Jurtz, N., Kraume, M. & Wehinger, G. D. Advances in fixed-bed reactor modeling using particle-resolved computational fluid dynamics (CFD). Rev. Chem. Eng. 35, 139–190 (2019).

    Google Scholar 

  21. 21.

    Buurmans, I. L. C. & Weckhuysen, B. M. Heterogeneities of individual catalyst particles in space and time as monitored by spectroscopy. Nat. Chem. 4, 873–886 (2012).

    CAS  PubMed  Google Scholar 

  22. 22.

    Urakawa, A. & Baiker, A. Space-resolved profiling relevant in heterogeneous catalysis. Top. Catal. 52, 1312–1322 (2009).

    CAS  Google Scholar 

  23. 23.

    Beale, A. M., Jacques, S. D. M. & Weckhuysen, B. M. Chemical imaging of catalytic solids with synchrotron radiation. Chem. Soc. Rev. 39, 4656–4672 (2010).

    CAS  PubMed  Google Scholar 

  24. 24.

    Sanchez, D. F. et al. 2D/3D microanalysis by energy dispersive X-ray absorption spectroscopy tomography. Sci. Rep. 7, 16453 (2017).

    PubMed  PubMed Central  Google Scholar 

  25. 25.

    Ihli, J. et al. A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts. Nat. Commun. 8, 809 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  26. 26.

    Sheppard, T. L. et al. In situ multimodal 3D chemical imaging of a hierarchically structured Core@Shell catalyst. J. Am. Chem. Soc. 139, 7855–7863 (2017).

    CAS  PubMed  Google Scholar 

  27. 27.

    Weker, J. N., Huang, X. & Toney, M. F. In situ X-ray-based imaging of nano materials. Curr. Op. Chem. Eng. 12, 14–21 (2016).

    Google Scholar 

  28. 28.

    Price, S. W. T. et al. Chemical imaging of single catalyst particles with scanning μ-XANES-CT and μ-XRF-CT. Phys. Chem. Chem. Phys. 17, 521–529 (2015).

    CAS  PubMed  Google Scholar 

  29. 29.

    Becher, J. et al. Mapping the pore architecture of structured catalyst monoliths from nanometer to centimeter scale with electron and X-ray tomographies. J. Phys. Chem. C 123, 25197–25208 (2019).

    CAS  Google Scholar 

  30. 30.

    Hofmann, G. et al. Aging of a Pt/Al2O3 exhaust gas catalyst monitored by quasi in situ X-ray micro computed tomography. RSC Adv. 5, 6893–6905 (2015).

    CAS  Google Scholar 

  31. 31.

    Meirer, F. et al. Mapping metals incorporation of a whole single catalyst particle using element specific X-ray nanotomography. J. Am. Chem. Soc. 137, 102–105 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  32. 32.

    Bossers, K. W. et al. Correlated X-ray ptychography and fluorescence nano-tomography on the fragmentation behavior of an individual catalyst particle during the early stages of olefin polymerization. J. Am. Chem. Soc. 142, 3691–3695 (2020).

    CAS  PubMed  PubMed Central  Google Scholar 

  33. 33.

    Price, S. W. T. et al. Chemical imaging of Fischer–Tropsch catalysts under operating conditions. Sci. Adv. 3, e1602838 (2017).

    PubMed  PubMed Central  Google Scholar 

  34. 34.

    Senecal, P. et al. Real-time scattering-contrast imaging of a supported cobalt-based catalyst body during activation and Fischer–Tropsch synthesis revealing spatial dependence of particle size and phase on catalytic properties. ACS Catal. 7, 2284–2293 (2017).

    CAS  Google Scholar 

  35. 35.

    Cats, K. et al. Active phase distribution changes within a catalyst particle during Fischer–Tropsch synthesis as revealed by multi-scale microscopy. Catal. Sci. Technol. 6, 4438–4449 (2016).

    CAS  Google Scholar 

  36. 36.

    Matras, D. et al. Operando and postreaction diffraction imaging of the La–Sr/CaO catalyst in the oxidative coupling of methane reaction. J. Phys. Chem. C 123, 1751–1760 (2019).

    CAS  Google Scholar 

  37. 37.

    Vamvakeros, A. et al. Real time chemical imaging of a working catalytic membrane reactor during oxidative coupling of methane. Chem. Commun. 51, 12752–12755 (2015).

    CAS  Google Scholar 

  38. 38.

    Vamvakeros, A. et al. 5D operando tomographic diffraction imaging of a catalyst bed. Nat. Commun. 9, 4751 (2018).

    CAS  PubMed  PubMed Central  Google Scholar 

  39. 39.

    Schmidt, J. E., Oord, R., Guo, W., Poplawsky, J. D. & Weckhuysen, B. M. Nanoscale tomography reveals the deactivation of automotive copper-exchanged zeolite catalysts. Nat. Commun. 8, 1666 (2017).

    PubMed  PubMed Central  Google Scholar 

  40. 40.

    Schmidt, J. E. et al. Probing the location and speciation of elements in zeolites with correlated atom probe tomography and scanning transmission X-ray microscopy. ChemCatChem 11, 488–494 (2019).

    CAS  PubMed  Google Scholar 

  41. 41.

    Paolucci, C. et al. Isolation of the copper redox steps in the standard selective catalytic reduction on Cu-SSZ-13. Angew. Chem. Int. Ed. 53, 11828–11833 (2014).

    CAS  Google Scholar 

  42. 42.

    Alayon, E. M. C., Nachtegaal, M., Kleymenov, E. & van Bokhoven, J. A. Determination of the electronic and geometric structure of Cu sites during methane conversion over Cu-MOR with X-ray absorption spectroscopy. Micropor. Mesopor. Mater. 166, 131–136 (2013).

    CAS  Google Scholar 

  43. 43.

    Zhang, R. & McEwen, J.-S. Local environment sensitivity of the Cu K-edge XANES features in Cu-SSZ-13: analysis from first-principles. J. Phys. Chem. Lett. 9, 3035–3042 (2018).

    CAS  PubMed  Google Scholar 

  44. 44.

    Bendrich, M., Scheuer, A., Hayes, R. E. & Votsmeier, M. Unified mechanistic model for standard SCR, fast SCR, and NO2 SCR over a copper chabazite catalyst. Appl. Catal. B 222, 76–87 (2018).

    CAS  Google Scholar 

  45. 45.

    Giordanino, F. et al. Interaction of NH3 with Cu-SSZ-13 catalyst: a complementary FTIR, XANES, and XES study. J. Phys. Chem. Lett. 5, 1552–1559 (2014).

    CAS  PubMed  Google Scholar 

  46. 46.

    Doronkin, D. E. et al. Operando spatially- and time-resolved XAS study on zeolite catalysts for selective catalytic reduction of NOx by NH3. J. Phys. Chem. C 118, 10204–10212 (2014).

    CAS  Google Scholar 

  47. 47.

    Gao, F., Mei, D., Wang, Y., Szanyi, J. & Peden, C. H. F. Selective catalytic reduction over Cu/SSZ-13: linking homo- and heterogeneous catalysis. J. Am. Chem. Soc. 139, 4935–4942 (2017).

    CAS  PubMed  Google Scholar 

  48. 48.

    Gao, F. et al. Understanding ammonia selective catalytic reduction kinetics over Cu/SSZ-13 from motion of the Cu ions. J. Catal. 319, 1–14 (2014).

    CAS  Google Scholar 

  49. 49.

    van Aarle, W. et al. Fast and flexible X-ray tomography using the ASTRA toolbox. Opt. Express 24, 25129–25147 (2016).

    PubMed  Google Scholar 

  50. 50.

    Ravel, B. & Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. J. Synchrotron Radiat. 12, 537–541 (2005).

    CAS  PubMed  Google Scholar 

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This work was supported by the German Federal Ministry of Education and Research (BMBF) projects MicTomoCat (no. 05K16VK1) and COSMIC (no. 05K19VK4), and the German Research Foundation project (no. GR 3987/5-1). Spectrotomography experiments were performed at beamline microXAS of the Swiss Light Source. We acknowledge the Paul Scherrer Institut, Villigen, Switzerland for provision of synchrotron radiation beamtime at beamline microXAS, and thank M. Birri, B. Meyer and D. Grolimund for technical assistance and scientific discussions. Additional energy-dispersive spectrotomography experiments were performed on beamline ID24 at the European Synchrotron Radiation Facility, Grenoble, France. We thank F. Perrin and S. Pasternak for technical assistance. Furthermore we thank T. Bergfeldt (IAM-AWP, Karlsruhe Institute of Technology) for elemental analysis of the ion-exchanged zeolite; we thank M. Casapu from the Karlsruhe Institute of Technology for discussions on NH3-SCR, P. Lott for assistance during beamtime and D. Yuda for assistance with design of the reaction set-up. D.Z. additionally thanks the Deutsche Bundesstiftung Umwelt for the scholarship provided. T.L.S. thanks the BMBF and project COSMIC for funding.

Author information




T.L.S., D.M.M., D.E.D. and J.-D.G. conceived and designed the experiments. J.B. and T.L.S. designed the spectrotomography set-up. J.B. and D.Z. synthesized the materials. J.B., D.F.S., D.E.D., D.M.M., S.P., J.-D.G. and T.L.S. contributed to preparation of beamtime proposals for access to synchrotron radiation. J.B., D.F.S., D.E.D., D.Z., D.M.M., S.P. and T.L.S. performed the experiments and acquired the data. D.F.S. and J.B. prepared code for processing of the raw data. J.B., D.F.S., D.E.D. and T.L.S performed analysis of the processed data and, with J.-D.G., interpreted the data. J.B., T.L.S. and D.E.D. drafted the manuscript, and all authors contributed to revision of the manuscript. J.-D.G. and T.L.S. were responsible for acquisition of funding.

Corresponding authors

Correspondence to Jan-Dierk Grunwaldt or Thomas L. Sheppard.

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The authors declare no competing interests.

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Peer review information Nature Catalysis thanks Jianjun Chen and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Methods, Discussion, Note 1, References, Figs. 1–18 and Tables 1–3.

Source data

Source Data Fig. 1

Percentage NO conversion versus time and temperature during ammonia SCR.

Source Data Fig. 2

Example of Cu K XANES data derived from operando spectrotomography.

Source Data Fig. 3

Cu XANES data from operando spectrotomography under SCR conditions from 200 to 400 °C and related linear combination fitting of XANES.

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Becher, J., Sanchez, D.F., Doronkin, D.E. et al. Chemical gradients in automotive Cu-SSZ-13 catalysts for NOx removal revealed by operando X-ray spectrotomography. Nat Catal 4, 46–53 (2021).

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