Reversible and cooperative photoactivation of single-atom Cu/TiO2 photocatalysts


The reversible and cooperative activation process, which includes electron transfer from surrounding redox mediators, the reversible valence change of cofactors and macroscopic functional/structural change, is one of the most important characteristics of biological enzymes, and has frequently been used in the design of homogeneous catalysts. However, there are virtually no reports on industrially important heterogeneous catalysts with these enzyme-like characteristics. Here, we report on the design and synthesis of highly active TiO2 photocatalysts incorporating site-specific single copper atoms (Cu/TiO2) that exhibit a reversible and cooperative photoactivation process. Our atomic-level design and synthetic strategy provide a platform that facilitates valence control of co-catalyst copper atoms, reversible modulation of the macroscopic optoelectronic properties of TiO2 and enhancement of photocatalytic hydrogen generation activity, extending the boundaries of conventional heterogeneous catalysts.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Cooperative photoactivation cycle of Cu/TiO2.
Fig. 2: Designing a site-specific single-atom photocatalyst.
Fig. 3: Characterization of single-atom catalysts.
Fig. 4: Photocatalytic H2 generation activity and spectroscopic characterization of Cu/TiO2.
Fig. 5: Characterization of the Cu/TiO2 photoactivation cycle mechanism through spectroscopic analysis
Fig. 6: Role of isolated Cu atoms in the cooperative interplay of Cu and TiO2.

Data availability

All data are available in the main text or in the Supplementary Information.


  1. 1.

    Hisatomi, T., Kubota, J. & Domen, K. Recent advances in semiconductors for photocatalytic and photoelectrochemical water splitting. Chem. Soc. Rev. 43, 7520–7535 (2014).

    CAS  Article  Google Scholar 

  2. 2.

    Hoffmann, M. R., Martin, S. T., Choi, W. & Bahnemann, D. W. Environmental applications of semiconductor photocatalysis. Chem. Rev. 95, 69–96 (1995).

    CAS  Article  Google Scholar 

  3. 3.

    Kudo, A. & Miseki, Y. Heterogeneous photocatalyst materials for water splitting. Chem. Soc. Rev. 38, 253–278 (2009).

    CAS  Article  Google Scholar 

  4. 4.

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

    Article  Google Scholar 

  5. 5.

    Cargnello, M. et al. Engineering titania nanostructure to tune and improve its photocatalytic activity. Proc. Natl Acad. Sci. USA 113, 3966–3971 (2016).

    CAS  Article  Google Scholar 

  6. 6.

    Gordon, T. R. et al. Nonaqueous synthesis of TiO2 nanocrystals using TiF4 to engineer mophology, oxygen vacancy concentration and photocatalytic activity. J. Am. Chem. Soc. 134, 6751–6761 (2012).

    CAS  Article  Google Scholar 

  7. 7.

    Choi, W., Termin, A. & Hoffmann, M. R. The role of metal ion dopants in quantum-sized TiO2: correlation between photoreactivity and charge carrier recombination dynamics. J. Phys. Chem. 98, 13669–13679 (1994).

    Article  Google Scholar 

  8. 8.

    Ran, J., Zhang, J., Yu, J., Jaroniec, M. & Qiao, S. Z. Earth-abundant cocatalysts for semiconductor-based photocatalytic water splitting. Chem. Soc. Rev. 43, 7787–7812 (2014).

    CAS  Article  Google Scholar 

  9. 9.

    Yang, H. G. et al. Anatase TiO2 single crystals with a large percentage of reactive facets. Nature 453, 638–641 (2008).

    Google Scholar 

  10. 10.

    Park, S. et al. Photocatalytic hydrogen generation from hydriodic acid using methylammonium lead iodide in dynamic equilibrium with aqueous solution. Nat. Energy 2, 16185 (2016).

    Article  Google Scholar 

  11. 11.

    Guo, Q. et al. Elementary photocatalytic chemistry on TiO2 surfaces. Chem. Soc. Rev. 45, 3701–3730 (2016).

    CAS  Article  Google Scholar 

  12. 12.

    Hussain, H. et al. Structure of a model TiO2 photocatalytic interface. Nat. Mater. 16, 461–466 (2017).

    Article  Google Scholar 

  13. 13.

    Wang, A., Li, J. & Zhang, T. Heterogeneous single-atom catalysis. Nat. Rev. Chem. 2, 65–81 (2018).

    CAS  Article  Google Scholar 

  14. 14.

    Qiao, B. et al. Single-atom catalysis of CO oxidation using Pt1/FeOx. Nat. Chem. 3, 634–641 (2011).

    Article  Google Scholar 

  15. 15.

    Liu, P. et al. Photochemical route for synthesizing atomically dispersed palladium catalysts. Science 352, 797–800 (2016).

    CAS  Article  Google Scholar 

  16. 16.

    Lin, L. et al. Low-temperature hydrogen production from water and methanol using Pt/α-MoC catalysts. Nature 544, 80–83 (2017).

    Article  Google Scholar 

  17. 17.

    Choi, C. H. et al. Tuning selectivity of electrochemical reactions by atomically dispersed platinum catalyst. Nat. Commun. 7, 10922 (2016).

    CAS  Article  Google Scholar 

  18. 18.

    Shan, J., Li, M., Allard, L. F., Lee, S. & Flytzani-Stephanopoulos, M. Mild oxidation of methane to methanol or acetic acid on supported isolated rhodium catalysts. Nature 551, 605–608 (2017).

    Article  Google Scholar 

  19. 19.

    Nie, L. et al. Activation of surface lattice oxygen in single-atom Pt/CeO2 for low-temperature CO oxidation. Science 358, 1419–1423 (2017).

    CAS  Article  Google Scholar 

  20. 20.

    DeRita, L. et al. Catalyst architecture for stable single atom dispersion enables site-specific spectroscopic and reactivity measurements of CO adsorbed to Pt atoms, oxidized Pt clusters, and metallic Pt clusters on TiO2. J. Am. Chem. Soc. 139, 14150–14165 (2017).

    CAS  Article  Google Scholar 

  21. 21.

    Benkovic, S. J. & Hammes-Schiffer, S. A perspective on enzyme catalysis. Science 301, 1196–1202 (2003).

    CAS  Article  Google Scholar 

  22. 22.

    Liu, J. et al. Metalloproteins containing cytochrome, iron–sulfur, or copper redox centers. Chem. Rev. 114, 4366–4469 (2014).

    CAS  Article  Google Scholar 

  23. 23.

    Que, L. Jr & Tolman, W. B. Biologically inspired oxidation catalysis. Nature 455, 333–340 (2008).

    Article  Google Scholar 

  24. 24.

    Wodrich, M. D. & Hu, X. Natural inspirations for metal–ligand cooperative catalysis. Nat. Rev. Chem. 2, 0099 (2017).

    Article  Google Scholar 

  25. 25.

    Piao, Y. et al. Wrap–bake–peel process for nanostructural transformation from β-FeOOH nanorods to biocompatible iron oxide nanocapsules. Nat. Mater. 7, 242 (2008).

    CAS  Article  Google Scholar 

  26. 26.

    Chen, X., Liu, L., Peter, Y. Y. & Mao, S. S. Increasing solar absorption for photocatalysis with black hydrogenated titanium dioxide nanocrystals. Science 331, 746–750 (2011).

    CAS  Article  Google Scholar 

  27. 27.

    Chen, X., Liu, L. & Huang, F. Black titanium dioxide (TiO2) nanomaterials. Chem. Soc. Rev. 44, 1861–1885 (2015).

    CAS  Article  Google Scholar 

  28. 28.

    Jung, D. et al. A molecular cross-linking approach for hybrid metal oxides. Nat. Mater. 17, 341–348 (2018).

    Google Scholar 

  29. 29.

    Selcuk, S., Zhao, X. & Selloni, A. Structural evolution of titanium dioxide during reduction in high-pressure hydrogen. Nat. Mater. 17, 923–928 (2018).

    CAS  Article  Google Scholar 

  30. 30.

    Zhou, W. et al. Ordered mesoporous black TiO2 as highly efficient hydrogen evolution photocatalyst. J. Am. Chem. Soc. 136, 9280–9283 (2014).

    CAS  Article  Google Scholar 

  31. 31.

    Neubert, S. et al. Highly efficient rutile TiO2 photocatalysts with single Cu(ii) and Fe(iii) surface catalytic sites. J. Mater. Chem. A 4, 3127–3138 (2016).

    CAS  Article  Google Scholar 

  32. 32.

    Siemer, N. et al. Atomic scale explanation of O2 activation at the Au–TiO2 interface. J. Am. Chem. Soc. 140, 18082–18092 (2018).

    CAS  Article  Google Scholar 

  33. 33.

    Hayyan, M., Hashim, M. A. & AlNashef, I. M. Superoxide ion: generation and chemical implications. Chem. Rev. 116, 3029–3085 (2016).

    CAS  Article  Google Scholar 

  34. 34.

    Kim, J. et al. Continuous O2-evolving MnFe2O4 nanoparticle-anchored mesoporous silica nanoparticles for efficient photodynamic therapy in hypoxic cancer. J. Am. Chem. Soc. 139, 10992–10995 (2017).

    CAS  Article  Google Scholar 

  35. 35.

    Krukau, A. V., Vydrov, O. A., Izmaylov, A. F. & Scuseria, G. E. Influence of the exchange screening parameter on the performance of screened hybrid functionals. J. Chem. Phys. 125, 224106 (2006).

    Article  Google Scholar 

  36. 36.

    Finazzi, E., Valentin, C. D., Pacchioni, G. & Selloni, A. Excess electron states in reduced bulk anatase TiO2: comparison of standard GGA, GGA + U and hybrid DFT calculations. J. Chem. Phys. 129, 154113 (2008).

    Article  Google Scholar 

  37. 37.

    Setvín, M. et al. Reaction of O2 with subsurface oxygen vacancies on TiO2 anatase (101). Science 341, 988–991 (2013).

    Article  Google Scholar 

  38. 38.

    Liu, H. et al. Crystallinity control of TiO2 hollow shells through resin-protected calcination for enhanced photocatalytic activity. Energy Environ. Sci. 8, 286–296 (2015).

    CAS  Article  Google Scholar 

  39. 39.

    Pennycook, S. J. & Jesson, D. E. High-resolution incoherent imaging of crystals. Phys. Rev. Lett. 64, 938–941 (1990).

    CAS  Article  Google Scholar 

  40. 40.

    Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    CAS  Article  Google Scholar 

  41. 41.

    Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    Article  Google Scholar 

  42. 42.

    Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

    CAS  Article  Google Scholar 

  43. 43.

    Kresse, G. & Hafner, J. Ab initio molecular dynamics for open-shell transition metals. Phys. Rev. B 48, 13115–13118 (1993).

    CAS  Article  Google Scholar 

  44. 44.

    Kresse, G. & Hafner, J. Ab initio molecular-dynamics simulation of the liquid-metal–amorphous-semiconductor transition in germanium. Phys. Rev. B 49, 14251–14269 (1994).

    CAS  Article  Google Scholar 

  45. 45.

    Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

    CAS  Article  Google Scholar 

  46. 46.

    Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    CAS  Article  Google Scholar 

  47. 47.

    Matsubara, M., Saniz, R., Partoens, B. & Lamoen, D. Doping anatase TiO2 with group V-b and VI-b transition metal atoms: a hybrid functional first-principles study. Phys. Chem. Chem. Phys. 19, 1945–1952 (2017).

    CAS  Article  Google Scholar 

  48. 48.

    Kokalj, A. Computer graphics and graphical user interfaces as tools in simulations of matter at the atomic scale. Comp. Mater. Sci. 28, 155–168 (2003).

    CAS  Article  Google Scholar 

Download references


Synthesis and physicochemical property analysis of the nanomaterial samples were supported by the Research Center Program of the IBS (IBS-R006-D1) in Korea (T.H.). Photocatalytic analysis was supported by the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2017M3D1A1039377). Computational work was supported by the Creative Materials Discovery Program (grant no. 2017M3D1A1039378) funded by the Korea government (MSIT). X-ray absorption spectroscopy work was supported by the Nano-Material Fundamental Technology Development programme (NRF-2018R1D1A1B07041997) through the NRF. The authors also thank the Korean Basic Science Institute (KBSI) at the Western Seoul Center for help with EPR measurements.

Author information




B.-H.L., S.P., H.K., K.T.N. and T.H. conceived the research. B.-H.L. and S.P. designed the experiments. B.-H.L., A.K.S., S.C.L. and E.J. performed and analysed the results. S.P., B.-H.L. and W.J.C. performed photochemical reactions. M.K. and H.K. performed the DFT calculations and analysis. S.-P.C. conducted the HAADF-STEM and EELS analysis. K.-S.L. contributed to the X-ray absorption spectroscopy experiments and analysis. B.-H.L., S.P., M.K., J.H.K., H.K., K.T.N. and T.H. wrote the manuscript. H.K., K.T.N. and T.H. supervised the project. All authors commented on the manuscript.

Corresponding authors

Correspondence to Hyungjun Kim or Ki Tae Nam or Taeghwan Hyeon.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Supplementary Information

Supplementary Figs. 1–23, Supplementary Tables 1–2, Supplementary refs. 1–13

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Lee, BH., Park, S., Kim, M. et al. Reversible and cooperative photoactivation of single-atom Cu/TiO2 photocatalysts. Nat. Mater. 18, 620–626 (2019).

Download citation

Further reading


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