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

Abstract

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.

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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.

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Acknowledgements

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.

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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.

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

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

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Lee, BH., Park, S., Kim, M. et al. Reversible and cooperative photoactivation of single-atom Cu/TiO2 photocatalysts. Nat. Mater. 18, 620–626 (2019). https://doi.org/10.1038/s41563-019-0344-1

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