Selecting between two transition states by which water oxidation intermediates decay on an oxide surface


Although catalytic mechanisms on electrode surfaces have been proposed for decades, the pathways by which the product’s chemical bonds evolve from the initial charge-trapping intermediates have not been resolved. Here, we discover a reactive intermediate population with states in the middle of a semiconductor’s bandgap that reveal the dynamics of two parallel transition state pathways for their decay. After phototriggering the water oxidation reaction from the n-SrTiO3 surface, the microsecond decay of the intermediates affirms transition state theory through two distinct time constants, the primary kinetic salt and H/D kinetic isotope effects, realistic activation barrier heights and transition state theory pre-factors. Furthermore, we show that the reaction conditions can be adjusted to allow selection between the two pathways, one characterized by a labile intermediate facing the electrolyte (the oxyl), and the other by a lattice oxygen (the bridge). In summary, we experimentally isolate an important activation barrier in multi-electron transfer water oxidation and, in doing so, identify competing mechanisms for O2 evolution at surfaces.

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Fig. 1: Spectra and kinetics of the oxyl and bridge radicals probed through subsurface vibration and the mid-gap electronic levels.
Fig. 2: The pH dependence and H/D KIE at the same ion density (0.2 M [Na+]).
Fig. 3: Ionic strength and temperature dependence at constant pH.
Fig. 4: Two competing reaction pathways.

Data availability

The representative data and all of the analysis from the extended dataset that support the findings of this paper are available in the paper and the Supplementary Information. The extended dataset that supports the findings in this paper is available from the corresponding author on reasonable request.


  1. 1.

    Hwang, J. et al. Perovskites in catalysis and electrocatalysis. Science 358, 751–756 (2017).

    CAS  Article  Google Scholar 

  2. 2.

    Seh, Z. W. et al. Combining theory and experiment in electrocatalysis: insights into materials design. Science 355, eaad4998 (2017).

    Article  Google Scholar 

  3. 3.

    Markovic, N. M. Electrocatalysis: interfacing electrochemistry. Nat. Mater. 12, 101–102 (2013).

    CAS  Article  Google Scholar 

  4. 4.

    Bockris, J. O. M. & Otagawa, T. The electrocatalysis of oxygen evolution on perovskites. J. Electrochem. Soc. 131, 290–302 (1984).

    CAS  Article  Google Scholar 

  5. 5.

    Surendranath, Y., Kanan, M. W. & Nocera, D. G. Mechanistic studies of the oxygen evolution reaction by a cobalt-phosphate catalyst at neutral pH. J. Am. Chem. Soc. 132, 16501–16509 (2010).

    CAS  Article  Google Scholar 

  6. 6.

    Yeo, B. S. & Bell, A. T. Enhanced activity of gold-supported cobalt oxide for the electrochemical evolution of oxygen. J. Am. Chem. Soc. 133, 5587–5593 (2011).

    CAS  Article  Google Scholar 

  7. 7.

    Seitz, L. et al. A highly active and stable IrOx/SrIrO3 catalyst for the oxygen evolution reaction. Science 353, 1011–1014 (2016).

    CAS  Article  Google Scholar 

  8. 8.

    Li, Y. F., Liu, Z. P., Liui, L. & Gao, W. Mechanism and activity of photocatalytic oxygen evolution on titania anatase in aqueous surroundings. J. Am. Chem. Soc. 132, 13008–13015 (2010).

    CAS  Article  Google Scholar 

  9. 9.

    Zhang, M. & Frei, H. Towards a molecular level understanding of the multi-electron catalysis of water oxidation on metal oxide surfaces. Catal. Lett. 145, 420–435 (2014).

    Article  Google Scholar 

  10. 10.

    Rossmeisl, J., Qu, Z. W., Zhu, H., Kroes, G. J. & Nørskov, J. K. Electrolysis of water on oxide surfaces. J. Electroanal. Chem. 607, 83–89 (2007).

    CAS  Article  Google Scholar 

  11. 11.

    Nørskov, J. K. et al. Universality in heterogeneous catalysis. J. Catal. 209, 275–278 (2002).

    Article  Google Scholar 

  12. 12.

    Pijpers, J. J. H., Winkler, M. T., Surendranath, Y., Buonassisi, T. & Nocera, D. G. Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst. Proc. Natl Acad. Sci. USA 108, 10056–10061 (2011).

    CAS  Article  Google Scholar 

  13. 13.

    Blakemore, J. D., Crabtree, R. H. & Brudvig, G. W. Molecular catalysts for water oxidation. Chem. Rev. 115, 12974–13005 (2015).

    CAS  Article  Google Scholar 

  14. 14.

    Yano, J. & Yachandra, V. K. Where water is oxidized to dioxygen: structure of the photosynthetic Mn4Ca cluster from X-ray spectroscopy. Inorg. Chem. 47, 1711–1726 (2008).

    CAS  Article  Google Scholar 

  15. 15.

    Askerka, M., Brudvig, G. W. & Batista, V. S. The O2-evolving complex of photosystem II: recent insights from quantum mechanics/molecular mechanics (QM/MM), extended X-ray absorption fine structure (EXAFS), and femtosecond X-ray crystallography data. Acc. Chem. Res. 50, 41–48 (2017).

    CAS  Article  Google Scholar 

  16. 16.

    Noguchi, T. Light-induced FTIR difference spectroscopy as a powerful tool toward understanding the molecular mechanism of photosynthetic oxygen evolution. Photo. Res. 91, 59–69 (2007).

    CAS  Article  Google Scholar 

  17. 17.

    Zaharieva, I., Wichmann, J. M. & Dau, H. Thermodynamic limitations of photosynthetic water oxidation at high proton concentrations. J. Bio. Chem. 286, 18222–18228 (2011).

    CAS  Article  Google Scholar 

  18. 18.

    Zaharieva, I., Dau, H. & Haumann, M. Sequential and coupled proton and electron transfer events in the S2 → S3 transition of photosynthetic water oxidation revealed by time-resolved X-ray absorption spectroscopy. Biochemistry 55, 6996–7004 (2016).

    CAS  Article  Google Scholar 

  19. 19.

    Herlihy, D. M. et al. Detecting the oxyl radical of photocatalytic water oxidation at an n-SrTiO3/aqueous interface through its subsurface vibration. Nat. Chem. 8, 549–555 (2016).

    CAS  Article  Google Scholar 

  20. 20.

    Zandi, O. & Hamann, T. W. Determination of photoelectrochemical water oxidation intermediates on haematite electrode surfaces using operando infrared spectroscopy. Nat. Chem. 8, 778–783 (2016).

    CAS  Article  Google Scholar 

  21. 21.

    Zhang, M., de Respinis, M. & Frei, H. Time-resolved observations of water oxidation intermediates on a cobalt oxide nanoparticle catalyst. Nat. Chem. 6, 362–367 (2014).

    CAS  Article  Google Scholar 

  22. 22.

    Pham, H. H., Cheng, M.-J., Frei, H. & Wang, L.-W. Surface proton hopping and fast-kinetics pathway of water oxidation on Co3O4 (001) surface. ACS Catal. 6, 5610–5617 (2016).

    CAS  Article  Google Scholar 

  23. 23.

    Cheng, J., Vandevondele, J. & Sprik, M. Identifying trapped electronic holes at the aqueous TiO2 interface. J. Phys. Chem. C 118, 5437–5444 (2014).

    CAS  Article  Google Scholar 

  24. 24.

    Formal, F. L. et al. Rate law analysis of water oxidation on a hematite surface. J. Am. Chem. Soc. 137, 6629–6637 (2015).

    Article  Google Scholar 

  25. 25.

    Pendlebury, S. R. et al. Ultrafast charge carrier recombination and trapping in hematite photoanodes under applied bias. J. Am. Chem. Soc. 136, 9854–9857 (2014).

    CAS  Article  Google Scholar 

  26. 26.

    Chen, X. et al. The formation time of Ti–O and Ti–O–Ti Radicals at the n-SrTiO3/aqueous interface during photocatalytic water oxidation. J. Am. Chem. Soc. 139, 1830–1841 (2017).

    CAS  Article  Google Scholar 

  27. 27.

    Aschaffenburg, D. J., Chen, X. & Cuk, T. Faradaic oxygen evolution from SrTiO3 under nano- and femto-second pulsed light excitation. Chem. Commun. 53, 7254–7257 (2017).

    CAS  Article  Google Scholar 

  28. 28.

    Likforman, J. P., Alexandrou, A., Joffre, M. & Fejer, M. Femtosecond white-light continuum generation in a Ti:sapphire oscillator. in Advanced Solid State Lasers (eds. Bosenberg, W & Fejer, M.) Vol. 19, TS5 (Optical Society of America, 1998).

  29. 29.

    Waegele, M. M., Chen, X., Herlihy, D. M. & Cuk, T. How surface potential determines the kinetics of the first hole transfer of photocatalytic water oxidation. J. Am. Chem. Soc. 136, 10632–10639 (2014).

    CAS  Article  Google Scholar 

  30. 30.

    Yamada, Y., Yasuda, H., Tayagaki, T. & Kanemitsu, Y. Photocarrier recombination dynamics in highly excited SrTiO3 studied by transient absorption and photoluminescence spectroscopy. Appl. Phys. Lett. 95, 121112 (2009).

    Article  Google Scholar 

  31. 31.

    Higuchi, T. et al. Electronic structure in the band gap of lightly doped SrTiO3 by high-resolution X-ray absorption spectroscopy. Phys. Rev. B 61, 12860–12863 (2000).

    CAS  Article  Google Scholar 

  32. 32.

    Mitra, C., Lin, C., Robertson, J. & Demkov, A. A. Electronic structure of oxygen vacancies in SrTiO3 and LaAlO3. Phys. Rev. B 86, 155105 (2012).

    Article  Google Scholar 

  33. 33.

    Janotti, A., Varley, J. B., Choi, M. & Van de Walle, C. G. Vacancies and small polarons in SrTiO3. Phys. Rev. B 90, 085202 (2014).

    Article  Google Scholar 

  34. 34.

    Chen, H. & Umezawa, N. Hole localization, migration, and the formation of peroxide anion in perovskite SrTiO3. Phys. Rev. B 90, 035202 (2014).

  35. 35.

    Guhl, H., Miller, W. & Reuter, K. Oxygen adatoms at SrTiO3(001): a density-functional theory study. Surf. Sci. 604, 372–376 (2010).

    CAS  Article  Google Scholar 

  36. 36.

    Kafizas, A. et al. Water oxidation kinetics of accumulated holes on the surface of a TiO2 photoanode: a rate law analysis. ACS Catal. 7, 4896–4903 (2017).

    CAS  Article  Google Scholar 

  37. 37.

    Norton, A. P., Bernasek, S. L. & Bocarsly, A. B. Mechanistic aspects of the photooxidation of water at the n-titania/aqueous interface: optically induced transients as a kinetic probe. J. Phys. Chem. 92, 6009–6016 (1988).

    CAS  Article  Google Scholar 

  38. 38.

    Zhang, Y. et al. Pivotal role and regulation of proton transfer in water oxidation on hematite photoanodes. J. Am. Chem. Soc. 138, 2705–2711 (2016).

    CAS  Article  Google Scholar 

  39. 39.

    De Stefano, C., Foti, C., Giuffrè, O. & Sammartano, S. Dependence on ionic strength of protonation enthalpies of polycarboxylate anions in NaCl aqueous solution. J. Chem. Eng. Data 46, 1417–1424 (2001).

    Article  Google Scholar 

  40. 40.

    Eyring, H. The activated complex in chemical reactions. J. Chem. Phys. 3, 107–115 (1935).

    CAS  Article  Google Scholar 

  41. 41.

    Lundberg, M., Blomberg, M. R. & Siegbahn, P. E. Oxyl radical required for O–O bond formation in synthetic Mn-catalyst. Inorg. Chem. 43, 264–274 (2004).

    CAS  Article  Google Scholar 

  42. 42.

    Li, X. & Siegbahn, P. E. Alternative mechanisms for O2 release and O–O bond formation in the oxygen evolving complex of photosystem II. Phys. Chem. Chem. Phys. 17, 12168–12174 (2015).

    CAS  Article  Google Scholar 

  43. 43.

    Bronsted, J. N. Theory of the chemical reaction rate. Z. Phys. Chem. 102, 169–207 (1922).

    CAS  Google Scholar 

  44. 44.

    Steinfeld, J. I., Francisco, J. S. & Hase, W. L. Chemical Kinetics and Dynamics 2nd edn (Prentice Hall, 1998).

  45. 45.

    Li, F. et al. Immobilizing Ru(bda) catalyst on a photoanode via electrochemical polymerization for light-driven water splitting. ACS Catal. 5, 3786–3790 (2015).

    CAS  Article  Google Scholar 

  46. 46.

    Oloo, W. N., Fielding, A. J. & Que, L. Rate-determining water-assisted O–O Bond Cleavage of an FeIII–OOH intermediate in a bio-inspired nonheme iron-catalyzed oxidation. J. Am. Chem. Soc. 135, 6438–6441 (2013).

    CAS  Article  Google Scholar 

  47. 47.

    Saavedra, J., Doan, H. A., Pursell, C. J., Grabow, L. C. & Chandler, B. D. The critical role of water at the gold-titania interface in catalytic CO oxidation. Science 345, 1599–1602 (2014).

    CAS  Article  Google Scholar 

  48. 48.

    Wijeratne, G. B., Day, V. W. & Jackson, T. A. O–H bond oxidation by a monomeric MnIII–OMe complex. Dalton Trans. 44, 3295–3306 (2015).p

    CAS  Article  Google Scholar 

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The experimental work was supported by the Director, Office of Science, Office of Basic Energy Sciences, and by the Division of Chemical Sciences, Geosciences and Biosciences of the US Department of Energy at LBNL under contract no. DE-AC02–05CH11231. We thank H. Frei and J. Eaves for fruitful discussions.

Author information




T.C. and X.C. conceived the project and T.C. wrote the manuscript with input from all authors. X.C and D.J.A constructed the transient set-up, collected transient data and prepared samples. X.C and T.C. analysed the transient data.

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Correspondence to Tanja Cuk.

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Supplementary Information

Supplementary Figs. 1–17, Tables 1–5, Notes 1–5 and references.

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Chen, X., Aschaffenburg, D.J. & Cuk, T. Selecting between two transition states by which water oxidation intermediates decay on an oxide surface. Nat Catal 2, 820–827 (2019).

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