Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

In situ electron paramagnetic resonance spectroscopy for catalysis


In situ catalysis studies seek insight into species present under reaction conditions to elucidate reaction mechanisms and understand the atomistic details of the active catalyst, both of which are key to optimizing catalyst reactivity and processes. Many reactions follow radical mechanisms, and many catalysts adopt paramagnetic states within their catalytic cycles where the systems exhibit species with unpaired electrons, which provide a sensitive handle to probe their geometric and electronic structure. Electron paramagnetic resonance (EPR) spectroscopy directly probes these unpaired electrons to characterize molecular radicals as well as determine transition metal ion oxidation states and coordination geometries. Here, we introduce the concept of EPR followed by the methodology for in situ EPR studies and discuss high-temperature gas–solid reactions, molecular catalysis, photocatalysis and electrocatalysis. The broad applicability of the approaches is demonstrated through case studies in each area, with a focus on unravelling catalytic mechanisms. We also discuss data sharing and reproducibility issues as well as limitations to the technique. Finally, we identify directions for development to guide interested researchers towards evolving areas including miniaturization and high-frequency analysis.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Crystal field splitting diagrams for CoII.
Fig. 2: Experimental set-ups for in situ EPR measurements during catalytic reactions.
Fig. 3: Origin of the shape of EPR spectra.
Fig. 4: EPR investigation of FeIII species in zeolites.
Fig. 5: Copper/TEMPO-catalysed selective oxidation of benzyl alcohol monitored by coupled in situ EPR/UV–Vis/ATR-IR/XAS.
Fig. 6: Photocatalytic water reduction in a homogeneous iron/iridium-containing system with triethylamine as a sacrificial agent.
Fig. 7: Heterogeneous photocatalytic formation of radicals from ozone for degradation of waste water pollutants.
Fig. 8: Reaction scheme for spin trapping radicals generated during SEC-EPR, and SEC-EPR of a cobalt oxide water oxidation catalyst correlating cobalt oxidation states with catalytic turnover.
Fig. 9: SEC-EPR of an immobilized alcohol oxidation catalyst.
Fig. 10: Thin film and liquid state EPRoC detection schemes.


  1. 1.

    Nørskov, J. K., Bligaard, T., Rossmeisl, J. & Christensen, C. H. Towards the computational design of solid catalysts. Nat. Chem. 1, 37–46 (2009).

    Article  Google Scholar 

  2. 2.

    Montoya, J. H. et al. Materials for solar fuels and chemicals. Nat. Mater. 16, 70–81 (2017).

    ADS  Article  Google Scholar 

  3. 3.

    Ertl, G. Reactions at surfaces: from atoms to complexity (Nobel Lecture). Angew. Chem. Int. Ed. 47, 3524–3535 (2008).

    Article  Google Scholar 

  4. 4.

    Louis, C., Lepetit, C. & Che, M. in Radicals on Surfaces (eds Lund, A. & Rhodes, C. J.) 3–38 (Springer Netherlands, 1995).

  5. 5.

    Dyrek, K. & Che, M. EPR as a tool to investigate the transition metal chemistry on oxide surfaces. Chem. Rev. 97, 305–332 (1997).

    Article  Google Scholar 

  6. 6.

    Risse, T., Hollmann, D. & Brückner, A. In situ electron paramagnetic resonance (EPR) — a unique tool for analysing structure and reaction behaviour of paramagnetic sites in model and real catalysts. Catalysis 27, 1–32 (2015).

    Article  Google Scholar 

  7. 7.

    Brückner, A. Monitoring transition metal ions (TMI) in oxide catalysts during (re)action: the power of operando EPR. Phys. Chem. Chem. Phys. 5, 4461–4472 (2003).

    Article  Google Scholar 

  8. 8.

    Abragam, A. & Bleaney, B. Electron Paramagnetic Resonance of Transition Ions (OUP, 2012). This seminal work on the paramagnetism of TMI still sets the standard for any description of the topic.

  9. 9.

    Brückner, A. In situ electron paramagnetic resonance: a unique tool for analyzing structure–reactivity relationships in heterogeneous catalysis. Chem. Soc. Rev. 39, 4673–4684 (2010). This article presents a short introduction of basic theoretical and experimental principles of EPR followed by selected application examples, including catalysts containing TMIs, radical anions such as O·– on oxide surfaces, and electrons in ferromagnetic particles and organic conductors.

    Article  Google Scholar 

  10. 10.

    Brustolon, M. & Giamello, E. Electron Paramagnetic Resonance: A Practitioners Toolkit (Wiley, 2009). This book presents easy-to-follow explanations of the core principles of EPR without overwhelming the reader with complex physics and mathematics. Instructive and relevant application examples illustrate strategies to solve problems.

  11. 11.

    Chechik, V., Carter, E. & Murphy, D. Electron Paramagnetic Resonance (Oxford Univ. Press, 2016). This thorough and well-written introduction to EPR is recommended for those with a chemistry background and is far more accessible than most detailed EPR texts.

  12. 12.

    Eaton, G. R., Eaton, S. S., Barr, D. P. & Weber, R. T. Quantitative EPR (Springer, 2010).

  13. 13.

    Goldfarb, D. & Stoll, S. EPR Spectroscopy: Fundamentals and Methods (Wiley, 2018). This state-of-the-art overview of advanced EPR techniques includes the theoretical principles of EPR and the calculation of EPR parameters, common experimental techniques such as pulse EPR, multi-frequency EPR and double resonance techniques, and important applications.

  14. 14.

    Pilbrow, J. R. Transition Ion Electron Paramagnetic Resonance (Clarendon Press, 1990). This introduction to EPR of TMIs is suitable for graduate students and scientists with a background in chemistry and physics who want to use this method for their own work, and includes many examples of TMIs in various materials such as oxides, glasses and semiconductors.

  15. 15.

    Poole, C. P. Electron Spin Resonance: A Comprehensive Treatise on Experimental Techniques 2nd edn (Dover, 1983). This comprehensive compilation of experimental techniques includes theoretical and practical aspects of ESR instrumentation.

  16. 16.

    Spencer, J., Folli, A., Richards, E. & Murphy, D. M. Electron Paramagnetic Resonance Vol. 26 130–170 (Royal Society of Chemistry, 2019). This review summarizes and highlights the applications of EPR in heterogeneous, homogeneous, photocatalytic and microporous materials, all of which are of vital importance to the field of catalysis.

  17. 17.

    Stoll, S. & Schweiger, A. EasySpin, a comprehensive software package for spectral simulation and analysis in EPR. J. Magn. Reson. 178, 42–55 (2006). This article presents the basic principles of EasySpin, the most versatile and powerful EPR simulation program. Anybody interested in the topic or the calculation of EPR spectra in general is strongly encouraged to visit the excellent EasySpin homepage maintained by Stefan Stoll.

    ADS  Article  Google Scholar 

  18. 18.

    Wadhawan, J. D. & Compton, R. G. in Encyclopedia of Electrochemistry (ed. Bard, A. J.) (Wiley, 2007). This book presents a chronological account of SEC-EPR.

  19. 19.

    Davies, M. J. Detection and characterisation of radicals using electron paramagnetic resonance (EPR) spin trapping and related methods. Methods 109, 21–30 (2016).

    Article  Google Scholar 

  20. 20.

    Barr, D. A step-by-step procedure for spin-trapping the hydroxyl radical. EPR Division of Bruker BioSpin Corp (Bruker, 1998).

  21. 21.

    Rehorek, D. Spin trapping of inorganic radicals. Chem. Soc. Rev. 20, 341–353 (1991).

    Article  Google Scholar 

  22. 22.

    Joseph, B. et al. In situ observation of conformational dynamics and protein ligand–substrate interactions in outer-membrane proteins with DEER/PELDOR spectroscopy. Nat. Protoc. 14, 2344–2369 (2019).

    Article  Google Scholar 

  23. 23.

    Mészáros, L. S., Németh, B., Esmieu, C., Ceccaldi, P. & Berggren, G. In vivo EPR characterization of semi-synthetic [FeFe] hydrogenases. Angew. Chem. 130, 2626–2629 (2018).

    Article  Google Scholar 

  24. 24.

    Schnegg, A., Behrends, J., Fehr, M. & Lips, K. Pulsed electrically detected magnetic resonance for thin film silicon and organic solar cells. Phys. Chem. Chem. Phys. 14, 14418–14438 (2012).

    Article  Google Scholar 

  25. 25.

    Cox, N., Pantazis, D. A., Neese, F. & Lubitz, W. Biological water oxidation. Acc. Chem. Res. 46, 1588–1596 (2013).

    Article  Google Scholar 

  26. 26.

    Lubitz, W., Reijerse, E. & van Gastel, M. [NiFe] and [FeFe] hydrogenases studied by advanced magnetic resonance techniques. Chem. Rev. 107, 4331–4365 (2007).

    Article  Google Scholar 

  27. 27.

    Rabeah, J. et al. Tracing active sites in supported Ni catalysts during butene oligomerization by operando spectroscopy under pressure. ACS Catal. 6, 8224–8228 (2016).

    Article  Google Scholar 

  28. 28.

    Godiksen, A. L., Funk, M. H., Rasmussen, S. B. & Mossin, S. Assessing the importance of VIV during NH3−SCR using operando EPR spectroscopy. ChemCatChem 12, 4893–4903 (2020).

    Article  Google Scholar 

  29. 29.

    Wang, F. et al. In situ EPR study of the redox properties of CuO–CeO2 catalysts for preferential CO oxidation (PROX). ACS Catal. 6, 3520–3530 (2016).

    Article  Google Scholar 

  30. 30.

    Zhang, Y. et al. Probing active-site relocation in Cu/SSZ-13 SCR catalysts during hydrothermal aging by in situ EPR spectroscopy, kinetics studies, and DFT calculations. ACS Catal. 10, 9410–9419 (2020).

    Article  Google Scholar 

  31. 31.

    Zichittella, G., Polyhach, Y., Tschaggelar, R., Jeschke, G. & Pérez-Ramírez, J. Quantification of redox sites during catalytic propane oxychlorination by operando EPR spectroscopy. Angew. Chem. 133, 3640–3646 (2021).

    Article  Google Scholar 

  32. 32.

    Brückner, A. Killing three birds with one stone — simultaneous operando EPR/UV–Vis/Raman spectroscopy for monitoring catalytic reactions. Chem. Commun. 2005, 1761–1763 (2005).

    Article  Google Scholar 

  33. 33.

    Rabeah, J. et al. Formation, operation and deactivation of Cr catalysts in ethylene tetramerization directly assessed by operando EPR and XAS. ACS Catal. 3, 95–102 (2013).

    Article  Google Scholar 

  34. 34.

    Grauke, R. et al. Impact of Al activators on structure and catalytic performance of Cr catalysts in homogeneous ethylene oligomerization — a multitechnique in situ/operando study. ChemCatChem 12, 1025–1035 (2019).

    Article  Google Scholar 

  35. 35.

    Brückner, A. & Kondratenko, E. Simultaneous operando EPR/UV–Vis/laser-Raman spectroscopy — a powerful tool for monitoring transition metal oxide catalysts during reaction. Catal. Today 113, 16–24 (2006).

    Article  Google Scholar 

  36. 36.

    Rabeah, J. et al. Multivariate analysis of coupled operando EPR/XANES/EXAFS/UV–Vis/ATR-IR spectroscopy: a new dimension for mechanistic studies of catalytic gas–liquid phase reactions. Chem. A Eur. J. 26, 7395–7404 (2020).

    Article  Google Scholar 

  37. 37.

    Murray, P. & Yellowlees, L. J. in Spectroelectrochemistry (eds Kaim, W. & Klein, A.) 207–231 (Royal Society of Chemistry, 2008).

  38. 38.

    Pauwels, D. et al. Identifying intermediates in the reductive intramolecular cyclisation of allyl 2-bromobenzyl ether by an improved electron paramagnetic resonance spectroelectrochemical electrode design combined with density functional theory calculations. Electrochim. Acta 271, 10–18 (2018).

    Article  Google Scholar 

  39. 39.

    Scheiring, T., Klein, A. & Kaim, W. EPR study of paramagnetic rhenium(I) complexes (bpy·)Re(CO)3X relevant to the mechanism of electrocatalytic CO2 reduction. J. Chem. Soc. Perkin Trans. 2, 2569–2572 (1997).

    Article  Google Scholar 

  40. 40.

    Kutin, Y., Cox, N., Lubitz, W., Schnegg, A. & Rüdiger, O. In situ EPR characterization of a cobalt oxide water oxidation catalyst at neutral pH. Catalysts 9, 926 (2019).

    Article  Google Scholar 

  41. 41.

    Hollmann, D. et al. From the precursor to the active state: monitoring metamorphosis of electrocatalysts during water oxidation by in situ spectroscopy. ChemElectroChem 4, 2117–2122 (2017).

    Article  Google Scholar 

  42. 42.

    Neukermans, S. et al. A versatile in-situ electron paramagnetic resonance spectro-electrochemical approach for electrocatalyst research. ChemElectroChem 7, 4578–4586 (2020).

    Article  Google Scholar 

  43. 43.

    Abdiaziz, K., Salvadori, E., Sokol, K. P., Reisner, E. & Roessler, M. M. Protein film electrochemical EPR spectroscopy as a technique to investigate redox reactions in biomolecules. Chem. Commun. 55, 8840–8843 (2019).

    Article  Google Scholar 

  44. 44.

    Janzen, E. G. Spin trapping. Acc. Chem. Res. 4, 31–40 (1971).

    Article  Google Scholar 

  45. 45.

    Buettner, G. R. Spin trapping: ESR parameters of spin adducts 1474 1528V. Free Radic. Biol. Med. 3, 259–303 (1987).

    Article  Google Scholar 

  46. 46.

    Gordy, W. Theory and Applications of Electron Spin Resonance Vol. 15 (Wiley, 1980).

  47. 47.

    Atherton, N. M. Principles of Electron Spin Resonance (Ellis Horwood, 1993).

  48. 48.

    Weil, J. A. & Bolton, J. R. Electron Paramagnetic Resonance: Elementary Theory and Practical Applications (Wiley, 2007).

  49. 49.

    Schneider, D. & Freed, J. H. in Biological Magnetic Resonance Vol. 8 1–76 (Plenum Press, 1989).

  50. 50.

    Mabbs, F. E. & Collison, D. Electron Paramagnetic Resonance of d Transition Metal Compounds (Elsevier, 2013).

  51. 51.

    Kaupp, M., Buhl, M. & Malkin, V. G. Calculation of NMR and EPR Parameters (Wiley Online Library, 2004).

  52. 52.

    Chiesa, M. et al. Electron magnetic resonance in heterogeneous photocatalysis research. J. Phys. Condens. Matter 31, 444001 (2019).

    Article  Google Scholar 

  53. 53.

    Polliotto, V., Livraghi, S. & Giamello, E. Electron magnetic resonance as a tool to monitor charge separation and reactivity in photocatalytic materials. Res. Chem. Intermed. 44, 3905–3921 (2018).

    Article  Google Scholar 

  54. 54.

    Bon, V., Brunner, E., Pöppl, A. & Kaskel, S. Unraveling structure and dynamics in porous frameworks via advanced in situ characterization techniques. Adv. Funct. Mater. 30, 1907847 (2020).

    Article  Google Scholar 

  55. 55.

    Bruckner, A., Kubias, B., Lücke, B. & Stößer, R. In-situ electron spin resonance study of vanadium phosphate catalysts during the selective oxidation of n-butane to maleic anhydride. Colloids Surf. A Physicochem. Eng. Asp. 115, 179–186 (1996).

    Article  Google Scholar 

  56. 56.

    Brückner, A., Rybarczyk, P., Kosslick, H., Wolf, G. U. & Baerns, M. in Studies in Surface Science and Catalysis Vol. 142 B 1141–1148 (Elsevier, 2002).

  57. 57.

    Brückner, A., Martin, A., Kubias, B. & Lücke, B. Structure of vanadium sites in VPO catalysts and their influence on the catalytic performance in selective O- and N-insertion reactions. J. Chem. Soc. Faraday Trans. 94, 2221–2225 (1998).

    Article  Google Scholar 

  58. 58.

    Brückner, A. et al. in Studies in Surface Science and Catalysis Vol. 130A 359–364 (Elsevier, 2000).

  59. 59.

    Brückner, A., Radnik, J., Hoang, D. L. & Lieske, H. In situ investigation of active sites in zirconia-supported chromium oxide catalysts during the aromatization of n-octane. Catal. Lett. 60, 183–189 (1999).

    Article  Google Scholar 

  60. 60.

    Vuong, T. H. et al. Efficient VOx/Ce1–xTixO2 catalysts for low-temperature NH3–SCR: reaction mechanism and active sites assessed by in situ/operando spectroscopy. ACS Catal. 7, 1693–1705 (2017).

    Article  Google Scholar 

  61. 61.

    Eriksen, K. M., Fehrmann, R. & Bjerrum, N. J. ESR investigations of sulfuric acid catalyst deactivation. J. Catal. 132, 263–265 (1991).

    Article  Google Scholar 

  62. 62.

    Vuong, T. H. et al. Synergistic effect of VOx and MnOx surface species for improved performance of V2O5/Ce0.5Ti0.5−xMnxO2−δ catalysts in low-temperature NH3–SCR of NO. Catal. Sci. Technol. 8, 6360–6374 (2018).

    Article  Google Scholar 

  63. 63.

    Pérez Vélez, R. et al. Identifying active sites for fast NH3–SCR of NO/NO2 mixtures over Fe–ZSM-5 by operando EPR and UV–Vis spectroscopy. J. Catal. 316, 103–111 (2014).

    Article  Google Scholar 

  64. 64.

    Aasa, R. Powder line shapes in the electron paramagnetic resonance spectra of high-spin ferric complexes. J. Chem. Phys. 52, 3919–3930 (1970).

    ADS  Article  Google Scholar 

  65. 65.

    Brückner, A. in Spectroscopy of Transition Metal Ions on Surfaces (eds Weckhuysen, B. M., Van der Voort Weckhuysen, P. & Catana, G.) 69–90 (Leuven Univ. Press, 2000).

  66. 66.

    Bruckner, A., Lohse, U. & Mehner, H. The incorporation of iron ions in AlPO4-5 molecular sieves after microwave synthesis studied by EPR and Mössbauer spectroscopy. Microporous Mesoporous Mater. 20, 207–215 (1998).

    Article  Google Scholar 

  67. 67.

    Hagen, W. R. EPR spectroscopy as a probe of metal centres in biological systems. Dalton Trans. 2006, 4415–4434 (2006).

    Article  Google Scholar 

  68. 68.

    Chabbra, S. et al. First experimental evidence for a bis-ethene chromium(I) complex forming from an activated ethene oligomerization catalyst. Sci. Adv. 6, eabd7057 (2020).

    ADS  Article  Google Scholar 

  69. 69.

    Carter, E. & Murphy, D. M. The role of low valent transition metal complexes in homogeneous catalysis: an EPR investigation. Top. Catal. 58, 759–768 (2015).

    Article  Google Scholar 

  70. 70.

    Samanipour, M., Ching, H. V., Sterckx, H., Maes, B. U. & Van Doorslaer, S. The non-innocent role of spin traps in monitoring radical formation in copper-catalyzed reactions. Appl. Magn. Reson. 51, 1529–1542 (2020).

    Article  Google Scholar 

  71. 71.

    Della Lunga, G., Pogni, R. & Basosi, R. Computer simulation of EPR spectra in the slow-motion region for copper complexes with nitrogen ligands. J. Phys. Chem. 98, 3937–3942 (1994).

    Article  Google Scholar 

  72. 72.

    Pasenkiewicz-Gierula, M., Subczynski, W. K. & Antholine, W. E. Rotational motion of square planar copper complexes in solution and phospholipid bilayer membranes. J. Phys. Chem. B 101, 5596–5606 (1997).

    Article  Google Scholar 

  73. 73.

    Dijksman, A., Arends, I. W. & Sheldon, R. A. CuII-nitroxyl radicals as catalytic galactose oxidase mimics. Org. Biomol. Chem. 1, 3232–3237 (2003).

    Article  Google Scholar 

  74. 74.

    Luckham, S. L. J., Folli, A., Platts, J. A., Richards, E. & Murphy, D. M. Unravelling the photochemical transformations of chromium(I) 1,3 bis(diphenylphosphino), [Cr(CO)4(dppp)]+, by EPR spectroscopy. Organometallics 38, 2523–2529 (2019).

    Article  Google Scholar 

  75. 75.

    Caretti, I., Keulemans, M., Verbruggen, S. W., Lenaerts, S. & Van Doorslaer, S. Light-induced processes in plasmonic gold/TiO2 photocatalysts studied by electron paramagnetic resonance. Top. Catal. 58, 776–782 (2015).

    Article  Google Scholar 

  76. 76.

    Smits, M., Ling, Y., Lenaerts, S. & Van Doorslaer, S. Photocatalytic removal of soot: unravelling of the reaction mechanism by EPR and in situ FTIR spectroscopy. ChemPhysChem 13, 4251–4257 (2012).

    Article  Google Scholar 

  77. 77.

    Hollmann, D. et al. Insights into the mechanism of photocatalytic water reduction by DFT-supported in situ EPR/Raman spectroscopy. Angew. Chem. Int. Ed. 50, 10246–10250 (2011).

    Article  Google Scholar 

  78. 78.

    Gärtner, F. et al. Light-driven hydrogen generation: efficient iron-based water reduction catalysts. Angew. Chem. Int. Ed. 48, 9962–9965 (2009).

    Article  Google Scholar 

  79. 79.

    Xiao, J. et al. Number of reactive charge carriers — a hidden linker between band structure and catalytic performance in photocatalysts. ACS Catal. 9, 8852–8861 (2019).

    Article  Google Scholar 

  80. 80.

    Xiao, J. et al. Fast electron transfer and •OH formation: key features for high activity in visible-light-driven ozonation with C3N4 catalysts. ACS Catal. 7, 6198–6206 (2017).

    Article  Google Scholar 

  81. 81.

    Xiao, J., Xie, Y., Rabeah, J., Brückner, A. & Cao, H. Visible-light photocatalytic ozonation using graphitic C3N4 catalysts: a hydroxyl radical manufacturer for wastewater treatment. Acc. Chem. Res. 53, 1024–1033 (2020).

    Article  Google Scholar 

  82. 82.

    Schubert, E., Hett, T., Schiemann, O. & NejatyJahromy, Y. EPR studies on the kinetics of the α-hydroxyethyl radical generated by Fenton-like chemistry. J. Magn. Reson. 265, 10–15 (2016).

    ADS  Article  Google Scholar 

  83. 83.

    Kanan, M. W. & Nocera, D. G. In situ formation of an oxygen-evolving catalyst in neutral water containing phosphate and Co2+. Science 321, 1072–1075 (2008).

    ADS  Article  Google Scholar 

  84. 84.

    Kanan, M. W. et al. Structure and valency of a cobalt-phosphate water oxidation catalyst determined by in situ X-ray spectroscopy. J. Am. Chem. Soc. 132, 13692–13701 (2010).

    Article  Google Scholar 

  85. 85.

    McAlpin, J. G. et al. EPR evidence for CoIV species produced during water oxidation at neutral pH. J. Am. Chem. Soc. 132, 6882–6883 (2010).

    Article  Google Scholar 

  86. 86.

    McAlpin, J. G. et al. Electronic structure description of a CoIII3CoIVO-4 cluster: a model for the paramagnetic intermediate in cobalt-catalyzed water oxidation. J. Am. Chem. Soc. 133, 15444–15452 (2011).

    Article  Google Scholar 

  87. 87.

    Leung, J. J. et al. Solar-driven reduction of aqueous CO2 with a cobalt bis(terpyridine)-based photocathode. Nat. Catal. 2, 354–365 (2019).

    Article  Google Scholar 

  88. 88.

    Bajada, M. A. et al. A precious-metal-free hybrid electrolyzer for alcohol oxidation coupled to CO2-to-syngas conversion. Angew. Chem. Int. Ed. 132, 15763–15771 (2020).

    Article  Google Scholar 

  89. 89.

    Fournier, M., Hoogeveen, D. A., Bonke, S. A., Spiccia, L. & Simonov, A. N. Cooperative silanetriolate-carboxylate sensitiser anchoring for outstanding stability and improved performance of dye-sensitised photoelectrodes. Sustain. Energy Fuels 2, 1707–1718 (2018).

    Article  Google Scholar 

  90. 90.

    Aasa, R. & Vänngård, T. EPR signal intensity and powder shapes: a reexamination. J. Magn. Reson. 19, 308–315 (1975).

    ADS  Google Scholar 

  91. 91.

    Dyrek, K., Madej, A., Mazur, E. & Rokosz, A. Standards for EPR measurements of spin concentration. Colloids Surf. 45, 135–144 (1990).

    Article  Google Scholar 

  92. 92.

    Dyrek, K., Rokosz, A., Madej, A. & Bidzińska, E. Quantitative EPR studies of transition metal ions in oxide, aluminosilicate and polymer matrices. Appl. Magn. Reson. 10, 319–338 (1996).

    Article  Google Scholar 

  93. 93.

    Tamski, M. A. et al. Quantitative measurements in electrochemical electron paramagnetic resonance. Electrochim. Acta 213, 802–810 (2016).

    Article  Google Scholar 

  94. 94.

    Cox, N. et al. Electronic structure of the oxygen-evolving complex in photosystem II prior to O–O bond formation. Science 345, 804 (2014).

    ADS  Article  Google Scholar 

  95. 95.

    Lubitz, W., Reijerse, E. J. & Messinger, J. Solar water-splitting into H2 and O2: design principles of photosystem II and hydrogenases. Energy Environ. Sci. 1, 15–31 (2008).

    Article  Google Scholar 

  96. 96.

    Rapatskiy, L. et al. Detection of the water-binding sites of the oxygen-evolving complex of photosystem II using W-band 17O electron–electron double resonance-detected NMR spectroscopy. J. Am. Chem. Soc. 134, 16619–16634 (2012).

    Article  Google Scholar 

  97. 97.

    Tamski, M. A., Macpherson, J. V., Unwin, P. R. & Newton, M. E. Electrochemical electron paramagnetic resonance utilizing loop gap resonators and micro-electrochemical cells. Phys. Chem. Chem. Phys. 17, 23438–23447 (2015).

    Article  Google Scholar 

  98. 98.

    Bonke, S. A., Bond, A. M., Spiccia, L. & Simonov, A. N. Parameterization of water electrooxidation catalyzed by metal oxides using fourier transformed alternating current voltammetry. J. Am. Chem. Soc. 138, 16095–16104 (2016).

    Article  Google Scholar 

  99. 99.

    Tesch, M. F. et al. Evolution of oxygen–metal electron transfer and metal electronic states during manganese oxide catalyzed water oxidation revealed with in situ soft X-ray spectroscopy. Angew. Chem. Int. Ed. 58, 3426–3432 (2019).

    Article  Google Scholar 

  100. 100.

    Cruickshank, P. A. et al. A kilowatt pulsed 94 GHz electron paramagnetic resonance spectrometer with high concentration sensitivity, high instantaneous bandwidth, and low dead time. Rev. Sci. Instrum. 80, 103102 (2009).

    ADS  Article  Google Scholar 

  101. 101.

    Schnegg, A. in eMagRes vol. 6 (eds, Goldfarb, D. & Stoll, S.) 115–132 (John Wiley & Sons, 2017).

  102. 102.

    Spitzbarth, M. et al. Time-, spectral- and spatially resolved EPR spectroscopy enables simultaneous monitoring of diffusion of different guest molecules in nano-pores. J. Magn. Reson. 283, 45–51 (2017).

    ADS  Article  Google Scholar 

  103. 103.

    Wessig, M., Spitzbarth, M., Drescher, M., Winter, R. & Polarz, S. Multiple scale investigation of molecular diffusion inside functionalized porous hosts using a combination of magnetic resonance methods. Phys. Chem. Chem. Phys. 17, 15976–15988 (2015).

    Article  Google Scholar 

  104. 104.

    Xiang, Z. & Xu, Y. The status quo and prospect of ESR imaging applications to study on catalysts. Appl. Magn. Reson. 12, 69–79 (1997).

    Article  Google Scholar 

  105. 105.

    Sathiya, M. et al. Electron paramagnetic resonance imaging for real-time monitoring of Li-ion batteries. Nat. Commun. 6, 6276 (2015).

    ADS  Article  Google Scholar 

  106. 106.

    Switala, L. E., Black, B. E., Mercovich, C. A., Seshadri, A. & Hornak, J. P. An electron paramagnetic resonance mobile universal surface explorer. J. Magn. Reson. 285, 18–25 (2017).

    ADS  Article  Google Scholar 

  107. 107.

    Wolfson, H., Ahmad, R., Twig, Y., Blank, A. & Kuppusamy, P. in Medical Imaging 2015: Biomedical Applications in Molecular, Structural, and Functional Imaging 941706 (International Society for Optics and Photonics, 2015).

  108. 108.

    Zgadzai, O. et al. Electron-spin-resonance dipstick. Anal. Chem. 90, 7830–7836 (2018).

    Article  Google Scholar 

  109. 109.

    Sidabras, J. W. et al. Extending electron paramagnetic resonance to nanoliter volume protein single crystals using a self-resonant microhelix. Sci. Adv. 5, eaay1394 (2019).

    ADS  Article  Google Scholar 

  110. 110.

    Abhyankar, N. et al. Scalable microresonators for room-temperature detection of electron spin resonance from dilute, sub-nanoliter volume solids. Sci. Adv. 6, eabb0620 (2020).

    ADS  Article  Google Scholar 

  111. 111.

    Anders, J., Angerhofer, A. & Boero, G. K-band single-chip electron spin resonance detector. J. Magn. Reson. 217, 19–26 (2012).

    ADS  Article  Google Scholar 

  112. 112.

    Anders, J. & Lips, K. MR to go. J. Magn. Reson. 306, 118–123 (2019).

    ADS  Article  Google Scholar 

  113. 113.

    Matheoud, A. V. et al. Single-chip electron spin resonance detectors operating at 50 GHz, 92 GHz, and 146 GHz. J. Magn. Reson. 278, 113–121 (2017).

    ADS  Article  Google Scholar 

Download references


S.A.B acknowledges a postdoctoral fellowship from the Alexander von Humboldt foundation. S.A.B and A.S acknowledge funding by the Max Planck Society and A.S. by the BMBF EPR-on-a-Chip network project (03SF0565). The authors thank M. Teucher (MPI CEC) for providing the data in Fig. 9.

Author information




The authors contributed equally to all aspects of the article.

Corresponding author

Correspondence to Angelika Brückner.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information

Nature Reviews Methods Primers thanks G. Liu, M. Roessler, M. Self-Eddine, O. Schiemann and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Related links



Active species

A key catalyst state in the catalytic cycle that enables catalytic activity, typically existing at or prior to the rate-determining step.


Molecules with one or more unpaired electrons.

Ligand field

The electronic field of a ligand that affects the valance orbital degeneracy of the metal centre within crystal/ligand field theory.

Relaxation times

The times characterizing the return of an excited spin system to the ground state, which has a direct consequence on the spectral shape. Short relaxation times broaden the lines, in some cases beyond detection, and vice versa. The longest relaxation times are typically found at cryogenic temperatures.

Freeze quenching

Rapid cooling of the sample during a reaction, such as by immersing a sample tube in a cryogenic liquid or spraying an aerosol of reaction solution onto a cryogenic surface.

Spin traps

Organic molecules that react with radicals to form more stable radicals.

Dielectric losses

Losses of microwave energy stored in the resonator due to electric dipole excitations resulting in heating of the system.

Analyte lifetime

The lifetime of the species to be analysed.

Rate-determining step

The slowest step of a catalytic cycle consisting of several reaction steps.

Catalytic turnover

A single pass of a catalytic cycle after which the catalyst returns to its initial state, from which it can enter into the next cycle.


An evacuated multi-walled quartz glass vessel to reduce heat transfer due to thermal conduction. Metal layers on the glass to supress radiative losses cannot be used inside microwave cavities.

Coherent spectral assignment

The coherent assignment of spectra from the same sample obtained from different spectroscopic experiments when the different data sets can be explained by the same chemical reaction.


An electrochemical technique on which a potential difference is applied and the current flow is measured as a function of time.

Zeeman interaction

The interaction of an unpaired electron with the external magnetic field.


Magnetic resonance splitting patterns in which a signal is split into two lines of the same intensity.


In the context of a spin trap, radical adducts are the molecules resulting from reaction of a radical with a spin trap.

Zero-field splitting (ZFS) constants

In spin systems with more than one unpaired electron, magnetic interaction between the latter splits the otherwise degenerated spin states already in the absence of an external magnetic field. D and E are a measure for this splitting and depend on the anisotropy of the paramagnetic centre, being zero for isotropic centres.

Free electron g value

The g value of a free electron in a vacuum, ge = 2.0023.

Helmholtz layer

(Also known as the electrical double layer). A build up by the ions of a solution being bound to a charged surface.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Bonke, S.A., Risse, T., Schnegg, A. et al. In situ electron paramagnetic resonance spectroscopy for catalysis. Nat Rev Methods Primers 1, 33 (2021).

Download citation


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing