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Charge separation via asymmetric illumination in photocatalytic Cu2O particles

Nature Energy volume 3, pages 655–663 (2018)Cite this article

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Abstract

Solar-driven photocatalytic reactions provide a potential route to sustainable fuels. These processes rely on the effective separation of photogenerated charges, and therefore understanding and exploring the driving force for charge separation is key to improving the photocatalytic performance. Here, using surface photovoltage microscopy, we demonstrate that the photogenerated charges can be separated effectively in a high-symmetry Cu2O photocatalyst particle by asymmetric light irradiation. The holes and electrons are transferred to the illuminated and shadow regions, respectively, of a single photocatalytic particle. Quantitative results show that the intrinsic difference between electron and hole mobilities enables a diffusion-controlled charge separation process, which is stronger than that caused by conventional built-in electric fields (40 mV versus 10 mV). Based on the findings, we assemble spatially separated redox co-catalysts on a single photocatalytic particle and, in doing so, enhance the performance for a model photocatalytic reaction by 300%. These findings highlight the driving force caused by charge mobility differences and the use of asymmetric light illumination for charge separation in photocatalysis.

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Fig. 1: Charge separation between the illuminated facet and shadow facet under asymmetric illumination.
Fig. 2: Impact of illumination symmetry on the charge separation.
Fig. 3: Homogeneous charge separation by built-in electric fields.
Fig. 4: Quantitative SPV analysis and theoretical simulation to understand diffused charge separation.
Fig. 5: Asymmetric co-catalyst assembly and its impact on charge separation.

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References

  1. Lewis, N. S. Research opportunities to advance solar energy utilization. Science 351, aad1920 (2016).

    Article  Google Scholar 

  2. Chen, S., Takata, T. & Domen, K. Particulate photocatalysts for overall water splitting. Nat. Rev. Mater. 2, 17050 (2017).

    Article  Google Scholar 

  3. Wang, Q. et al. Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1%. Nat. Mater. 15, 611–615 (2016).

    Article  Google Scholar 

  4. Sambur, J. B. et al. Sub-particle reaction and photocurrent mapping to optimize catalyst-modified photoanodes. Nature 530, 77–80 (2016).

    Article  Google Scholar 

  5. Yang, Y. et al. Semiconductor interfacial carrier dynamics via photoinduced electric fields. Science 350, 1061–1065 (2015).

    Article  Google Scholar 

  6. Abdi, F. F. et al. Efficient solar water splitting by enhanced charge separation in a bismuth vanadate–silicon tandem photoelectrode. Nat. Commun. 4, 2195 (2013).

    Article  Google Scholar 

  7. Liu, M. et al. Photocatalytic hydrogen production using twinned nanocrystals and an unanchored NiSx co-catalyst. Nat. Energy 1, 16151 (2016).

    Article  Google Scholar 

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

    Article  Google Scholar 

  9. Zhang, J., Xu, Q., Feng, Z., Li, M. & Li, C. Importance of the relationship between surface phases and photocatalytic activity of TiO2. Angew. Chem. Int. Ed. 47, 1766–1769 (2008).

    Article  Google Scholar 

  10. Wang, X. et al. Photocatalytic overall water splitting promoted by an alpha-beta phase junction on Ga2O3. Angew. Chem. Int. Ed. 51, 13089–13092 (2012).

    Article  Google Scholar 

  11. Moniz, S. J. A., Shevlin, S. A., Martin, D. J., Guo, Z. X. & Tang, J. W. Visible-light driven heterojunction photocatalysts for water splitting—a critical review. Energy Environ. Sci. 8, 731–759 (2015).

    Article  Google Scholar 

  12. Wang, H. L. et al. Semiconductor heterojunction photocatalysts: design, construction, and photocatalytic performances. Chem. Soc. Rev. 43, 5234–5244 (2014).

    Article  Google Scholar 

  13. Li, R. et al. Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4. Nat. Commun. 4, 1432 (2013).

    Article  Google Scholar 

  14. Liu, G. et al. Titanium dioxide crystals with tailored facets. Chem. Rev. 114, 9559–9612 (2014).

    Article  Google Scholar 

  15. Baxter, J. B., Richter, C. & Schmuttenmaer, C. A. Ultrafast carrier dynamics in nanostructures for solar fuels. Annu. Rev. Phys. Chem. 65, 423–447 (2014).

    Article  Google Scholar 

  16. Takanabe, K. Solar water splitting using semiconductor photocatalyst powders. Top. Curr. Chem. 371, 73–103 (2016).

    Article  Google Scholar 

  17. Schafer, S., Wang, Z., Zierold, R., Kipp, T. & Mews, A. Laser-induced charge separation in CdSe nanowires. Nano. Lett. 11, 2672–2677 (2011).

    Article  Google Scholar 

  18. Mora-Seró, I., Dittrich, T., Garcia-Belmonte, G. & Bisquert, J. Determination of spatial charge separation of diffusing electrons by transient photovoltage measurements. J. Appl. Phys. 100, 103705 (2006).

    Article  Google Scholar 

  19. Paracchino, A., Laporte, V., Sivula, K., Gratzel, M. & Thimsen, E. Highly active oxide photocathode for photoelectrochemical water reduction. Nat. Mater. 10, 456–461 (2011).

    Article  Google Scholar 

  20. Wick, R. & Tilley, S. D. Photovoltaic and photoelectrochemical solar energy conversion with Cu2O. J. Phys. Chem. C. 119, 26243–26257 (2015).

    Article  Google Scholar 

  21. Hara, M. et al. Cu2O as a photocatalyst for overall water splitting under visible light irradiation. Chem.Commun. 0, 357–358 (1998).

    Google Scholar 

  22. Luo, J. S. et al. Cu2O nanowire photocathodes for efficient and durable solar water splitting. Nano Lett. 16, 1848–1857 (2016).

    Article  Google Scholar 

  23. Tan, C. S., Hsu, S. C., Ke, W. H., Chen, L. J. & Huang, M. H. Facet-dependent electrical conductivity properties of Cu2O crystals. Nano Lett. 15, 2155–2160 (2015).

    Article  Google Scholar 

  24. Li, R., Tao, X., Chen, R., Fan, F. & Li, C. Synergetic effect of dual co-catalysts on the activity of p-type Cu2O crystals with anisotropic facets. Chem. Eur. J. 21, 14337–14341 (2015).

    Article  Google Scholar 

  25. Li, L., Salvador, P. A. & Rohrer, G. S. Photocatalysts with internal electric fields. Nanoscale 6, 24–42 (2014).

    Article  Google Scholar 

  26. Nonnenmacher, M., O’Boyle, M. P. & Wickramasinghe, H. K. Kelvin probe force microscopy. Appl. Phys. Lett. 58, 2921 (1991).

    Article  Google Scholar 

  27. Melitz, W., Shen, J., Kummel, A. C. & Lee, S. Kelvin probe force microscopy and its application. Surf. Sci. Rep. 66, 1–27 (2011).

    Article  Google Scholar 

  28. Chen, R., Zhu, J., An, H., Fan, F. & Li, C. Unravelling charge separation via surface built-in electric fields within single particulate photocatalysts. Faraday Discuss. 198, 473–479 (2017).

    Article  Google Scholar 

  29. Tennyson, E. M. et al. Nanoimaging of open-circuit voltage in photovoltaic devices. Adv. Energy Mater. 5, 1501142 (2015).

    Article  Google Scholar 

  30. Haase, G. Surface photovoltage imaging for the study of local electronic structure at semiconductor surfaces. Int. Rev. Phys. Chem. 19, 247–276 (2000).

    Article  Google Scholar 

  31. Kronik, L. & Shapira, Y. Surface photovoltage phenomena: theory, experiment, and applications. Surf. Sci. Rep. 37, 1–206 (1999).

    Article  Google Scholar 

  32. Zhao, J. & Osterloh, F. E. Photochemical charge separation in nanocrystal photocatalyst films: insights from surface photovoltage spectroscopy. J. Phys. Chem. Lett. 5, 782–786 (2014).

    Article  Google Scholar 

  33. Zhu, J. et al. Direct imaging of highly anisotropic photogenerated charge separations on different facets of a single BiVO4 photocatalyst. Angew. Chem. Int. Ed. 54, 9111–9114 (2015).

    Article  Google Scholar 

  34. Wang, J., Zhao, J. & Osterloh, F. E. Photochemical charge transfer observed in nanoscale hydrogen evolving photocatalysts using surface photovoltage spectroscopy. Energy Environ. Sci. 8, 2970–2976 (2015).

    Article  Google Scholar 

  35. Zhang, Z. & Yates, J. T. Jr Band bending in semiconductors: chemical and physical consequences at surfaces and interfaces. Chem. Rev. 112, 5520–5551 (2012).

    Article  Google Scholar 

  36. McShane, C. M. & Choi, K. S. Photocurrent enhancement of n-type Cu2O electrodes achieved by controlling dendritic branching growth. J. Am. Chem. Soc. 131, 2561–2569 (2009).

    Article  Google Scholar 

  37. Wang, W., Wu, D., Zhang, Q., Wang, L. & Tao, M. pH-dependence of conduction type in cuprous oxide synthesized from solution. J. Appl. Phys. 107, 123717 (2010).

    Article  Google Scholar 

  38. McShane, C. M. & Choi, K. S. Junction studies on electrochemically fabricated p-n Cu2O homojunction solar cells for efficiency enhancement. Phys. Chem. Chem. Phys. 14, 6112–6118 (2012).

    Article  Google Scholar 

  39. Kibria, M. G. et al. Visible light-driven efficient overall water splitting using p-type metal–nitride nanowire arrays. Nat. Commun. 6, 6797 (2015).

    Article  Google Scholar 

  40. Zhang, S. F. et al. On the carrier injection efficiency and thermal property of InGaN/GaN axial nanowire light emitting diodes. IEEE J. Quantum Elect. 50, 483–490 (2014).

    Article  Google Scholar 

  41. Gao, Y. et al. Directly probing charge separation at Interface of TiO2 phase junction. J. Phys. Chem. Lett. 8, 1419–1423 (2017).

    Article  Google Scholar 

  42. Ziegler, D. & Stemmer, A. Force gradient sensitive detection in lift-mode Kelvin probe force microscopy. Nanotechnology 22, 075501 (2011).

    Article  Google Scholar 

  43. Barbet, S. et al. Cross-talk artefacts in Kelvin probe force microscopy imaging: a comprehensive study. J. Appl. Phys. 115, 144313 (2014).

    Article  Google Scholar 

  44. Colchero, J., Gil, A. & Baró, A. M. Resolution enhancement and improved data interpretation in electrostatic force microscopy. Phys. Rev. B 64, 245403 (2001).

    Article  Google Scholar 

  45. Hagfeldt, A. & Gratzel, M. Light-induced redox reactions in nanocrystalline systems. Chem. Rev. 95, 49–68 (1995).

    Article  Google Scholar 

  46. Dember, H. A photoelectrical-motor energy in copper-oxide crystals. Phys. Z. 32, 554–556 (1931).

    Google Scholar 

  47. Goldman, S. R., Kalikstein, K. & Kramer, B. Dember-effect theory. J. Appl. Phys. 49, 2849–2854 (1978).

    Article  Google Scholar 

  48. Chen, M. et al. Light-driven overall water splitting enabled by a photo-Dember effect realized on 3D plasmonic structures. ACS Nano 10, 6693–6701 (2016).

    Article  Google Scholar 

  49. Madelung, O. Semiconductors: Data Handbook (Springer, Berlin, Heidelberg, 2004).

  50. Musselman, K. P., Marin, A., Schmidt-Mende, L. & MacManus-Driscoll, J. L. Incompatible length scales in nanostructured Cu2O solar cells. Adv. Funct. Mater. 22, 2202–2208 (2012).

    Article  Google Scholar 

  51. Siegfried, M. J. & Choi, K. S. Electrochemical crystallization of cuprous oxide with systematic shape evolution. Adv. Mater. 16, 1743–1746 (2004).

    Article  Google Scholar 

  52. Siegfried, M. J. & Choi, K. S. Elucidating the effect of additives on the growth and stability of Cu2O surfaces via shape transformation of pre-grown crystals. J. Am. Chem. Soc. 128, 10356–10357 (2006).

    Article  Google Scholar 

  53. Nian, J.-N., Tsai, C.-C., Lin, P.-C. & Teng, H. Elucidating the conductivity-type transition mechanism of p-type Cu2O films from electrodeposition. J. Electrochem. Soc. 156, H567 (2009).

    Article  Google Scholar 

  54. Sommerhalter, C., Glatzel, T., Matthes, T. W., Jager-Waldau, A. & Lux-Steiner, M. C. Kelvin probe force microscopy in ultra high vacuum using amplitude modulation detection of the electrostatic forces. Appl. Surf. Sci. 157, 263–268 (2000).

    Article  Google Scholar 

  55. Gross, D. et al. Charge separation in Type II tunneling multilayered structures of CdTe and CdSe nanocrystals directly proven by surface photovoltage spectroscopy. J. Am. Chem. Soc. 132, 5981–5983 (2010).

    Article  Google Scholar 

  56. de Jongh, P. E. & Vanmaekelbergh, D. Trap-limited electronic transport in assemblies of nanometer-size TiO2 particles. Phys. Rev. Lett. 77, 3427–3430 (1996).

    Article  Google Scholar 

  57. Yang, Y. et al. Top and bottom surfaces limit carrier lifetime in lead iodide perovskite films. Nat. Energy 2, 16207 (2017).

    Article  Google Scholar 

  58. Huang, M. H., Rej, S. & Chiu, C. Y. Facet-dependent optical properties revealed through investigation of polyhedral Au–Cu2O and bimetallic core–shell nanocrystals. Small 11, 2716–2726 (2015).

    Article  Google Scholar 

  59. Lee, S., Liang, C. W. & Martin, L. W. Synthesis, control, and characterization of surface properties of Cu2O nanostructures. ACS Nano 5, 3736–3743 (2011).

    Article  Google Scholar 

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (grant no. 21633015, 21773228), the National Key Basic Research Program of China (973 Program, grant no. 2014CB239403) and the Strategic Priority Research Program and Equipment Development Project of the Chinese Academy of Sciences, grant no. XDB17000000, YJKYYQ20170002.

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Authors and Affiliations

  1. State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, The Collaborative Innovation Centre of Chemistry for Energy Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China

    Ruotian Chen, Shan Pang, Hongyu An, Jian Zhu, Sheng Ye, Yuying Gao, Fengtao Fan & Can Li

  2. University of Chinese Academy of Sciences, Beijing, China

    Ruotian Chen, Hongyu An & Yuying Gao

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  1. Ruotian Chen
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Contributions

R.C. conceived and conducted most of experiments, and analysed data; S.P. conducted the theoretical simulation; H.A. analysed the SPV data and conducted Raman measurements; J.Z. helped in the SPVM measurements; S.Y. helped in the activity measurements; Y.G. analysed KPFM data; F.F. conceived most of the experiments and analysed data. The manuscript was written by R.C. and F.F.; C.L. proposed the project, analysed data and revised the manuscript.

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Correspondence to Fengtao Fan or Can Li.

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Chen, R., Pang, S., An, H. et al. Charge separation via asymmetric illumination in photocatalytic Cu2O particles. Nat Energy 3, 655–663 (2018). https://doi.org/10.1038/s41560-018-0194-0

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