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Nanoscale semiconductor/catalyst interfaces in photoelectrochemistry

Abstract

Semiconductor structures (for example, films, wires, particles) used in photoelectrochemical devices are often decorated with nanoparticles that catalyse fuel-forming reactions, including water oxidation, hydrogen evolution or carbon-dioxide reduction. For high performance, the catalyst nanoparticles must form charge-carrier-selective contacts with the underlying light-absorbing semiconductor, facilitating either hole or electron transfer while inhibiting collection of the opposite carrier. Despite the key role played by such selective contacts in photoelectrochemical energy conversion and storage, the underlying nanoscale interfaces are poorly understood because direct measurement of their properties is challenging, especially under operating conditions. Using an n-Si/Ni photoanode model system and potential-sensing atomic force microscopy, we measure interfacial electron-transfer processes and map the photovoltage generated during photoelectrochemical oxygen evolution at nanoscopic semiconductor/catalyst interfaces. We discover interfaces where the selectivity of low-Schottky-barrier n-Si/Ni contacts for holes is enhanced via a nanoscale size-dependent pinch-off effect produced when surrounding high-barrier regions develop during device operation. These results thus demonstrate (1) the ability to make nanoscale operando measurements of contact properties under practical photoelectrochemical conditions and (2) a design principle to control the flow of electrons and holes across semiconductor/catalyst junctions that is broadly relevant to different photoelectrochemical devices.

Fig. 1: Characteristics of photoanodes fabricated by electrodeposition of Ni nanoislands onto n-Si.
Fig. 2: Characterization of n-Si/Ni photoelectrodes obtained from 5-s deposition.
Fig. 3: Simulations showing how the pinch-off model explains performance enhancements with catalyst nanocontacts.
Fig. 4: Dual-working-electrode device measurement shows that high-barrier contacts are formed from oxidized NiOOH during operation.
Fig. 5: n-Si/Ni nanocontacts produce a pinched-off junction following activation.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Code availability

Code used for the pinch-off simulations can be downloaded as a Supplementary Information file.

References

  1. 1.

    Sivula, K. & van de Krol, R. Semiconducting materials for photoelectrochemical energy conversion. Nat. Rev. Mater. 1, 15010 (2016).

    CAS  Google Scholar 

  2. 2.

    Chen, R. T., Fan, F. T., Dittrich, T. & Li, C. Imaging photogenerated charge carriers on surfaces and interfaces of photocatalysts with surface photovoltage microscopy. Chem. Soc. Rev. 47, 8238–8262 (2018).

    CAS  Google Scholar 

  3. 3.

    Mei, B., Han, K. & Mul, G. D. Driving surface redox reactions in heterogeneous photocatalysis: the active state of illuminated semiconductor-supported nanoparticles during overall water-splitting. ACS Catal. 8, 9154–9164 (2018).

    CAS  Google Scholar 

  4. 4.

    Laskowski, F. A. L., Nellist, M. R., Qu, J. J. & Boettcher, S. W. Metal oxide/(oxy)hydroxide overlayers as hole collectors and oxygen-evolution catalysts on water-splitting photoanodes. J. Am. Chem. Soc. 141, 1394–1405 (2019).

    CAS  Google Scholar 

  5. 5.

    Laskowski, F. A. L., Nellist, M. R., Venkatkarthick, R. & Boettcher, S. W. Junction behavior of n-Si photoanodes protected by thin Ni elucidated from dual working electrode photoelectrochemistry. Energy Environ. Sci. 10, 570–579 (2017).

    CAS  Google Scholar 

  6. 6.

    Tung, R. T. The physics and chemistry of the Schottky barrier height. Appl. Phys. Rev. 1, 011304 (2014).

    Google Scholar 

  7. 7.

    Tung, R. T. Electron-transport of inhomogeneous Schottky barriers. Appl. Phys. Lett. 58, 2821–2823 (1991).

    CAS  Google Scholar 

  8. 8.

    Tennyson, E. M., Gong, C. & Leite, M. S. Imaging energy harvesting and storage systems at the nanoscale. ACS Energy Lett. 2, 2761–2777 (2017).

    CAS  Google Scholar 

  9. 9.

    Collins, L. et al. Probing charge screening dynamics and electrochemical processes at the solid-liquid interface with electrochemical force microscopy. Nat. Commun. 5, 3871 (2014).

    CAS  Google Scholar 

  10. 10.

    Collins, L., Kilpatrick, J. I., Kalinin, S. V. & Rodriguez, B. J. Towards nanoscale electrical measurements in liquid by advanced KPFM techniques: a review. Rep. Prog. Phys. 81, 086101 (2018).

    Google Scholar 

  11. 11.

    Eichhorn, J. et al. Nanoscale imaging of charge carrier transport in water splitting photoanodes. Nat. Commun. 9, 2597 (2018).

    Google Scholar 

  12. 12.

    Esposito, D. V., Levin, I., Moffat, T. P. & Talin, A. A. H2 evolution at Si-based metal-insulator-semiconductor photoelectrodes enhanced by inversion channel charge collection and H spillover. Nat. Mater. 12, 562–568 (2013).

    CAS  Google Scholar 

  13. 13.

    Mariano, R. G., McKelvey, K., White, H. S. & Kanan, M. W. Selective increase in CO2 electroreduction activity at grain-boundary surface terminations. Science 358, 1187–1191 (2017).

    CAS  Google Scholar 

  14. 14.

    Hurth, C., Li, C. Z. & Bard, A. J. Direct probing of electrical double layers by scanning electrochemical potential microscopy. J. Phys. Chem. C 111, 4620–4627 (2007).

    CAS  Google Scholar 

  15. 15.

    Yoon, Y. H., Woo, D. H., Shin, T., Chung, T. D. & Kang, H. Real-space investigation of electrical double layers. Potential gradient measurement with a nanometer potential probe. J. Phys. Chem. C 115, 17384–17391 (2011).

    CAS  Google Scholar 

  16. 16.

    Nellist, M. R. et al. Potential-sensing electrochemical atomic force microscopy for in operando analysis of water-splitting catalysts and interfaces. Nat. Energy 3, 46–52 (2018).

    CAS  Google Scholar 

  17. 17.

    Loget, G., Fabre, B., Fryars, S., Meriadec, C. & Ababou-Girard, S. Dispersed Ni nanoparticles stabilize silicon photoanodes for efficient and inexpensive sunlight-assisted water oxidation. ACS Energy Lett. 2, 569–573 (2017).

    CAS  Google Scholar 

  18. 18.

    Kenney, M. J. et al. High-performance silicon photoanodes passivated with ultrathin nickel films for water oxidation. Science 342, 836–840 (2013).

    CAS  Google Scholar 

  19. 19.

    Oh, K. et al. Elucidating the performance and unexpected stability of partially coated water-splitting silicon photoanodes. Energy Environ. Sci. 11, 2590–2599 (2018).

    CAS  Google Scholar 

  20. 20.

    Loget, G. Water oxidation with inhomogeneous metal-silicon interfaces. Curr. Opin. Colloid Interface Sci. 39, 40–50 (2019).

    CAS  Google Scholar 

  21. 21.

    Sullivan, J. P., Tung, R. T., Pinto, M. R. & Graham, W. R. Electron-transport of inhomogeneous Schottky barriers - a numerical study. J. Appl. Phys. 70, 7403–7424 (1991).

    CAS  Google Scholar 

  22. 22.

    Tung, R. T. Electron-transport at metal-semiconductor interfaces - general theory. Phys. Rev. B 45, 13509–13523 (1992).

    CAS  Google Scholar 

  23. 23.

    Hill, J. C., Landers, A. T. & Switzer, J. A. An electrodeposited inhomogeneous metal-insulator-semiconductor junction for efficient photoelectrochemical water oxidation. Nat. Mater. 14, 1150–1155 (2015).

    CAS  Google Scholar 

  24. 24.

    Roe, E. T., Egelhofer, K. E. & Lonergan, M. C. Limits of contact selectivity/recombination on the open-circuit voltage of a photovoltaic. ACS. Appl. Energy. Mater. 1, 1037–1046 (2018).

    CAS  Google Scholar 

  25. 25.

    Rossi, R. C., Tan, M. X. & Lewis, N. S. Size-dependent electrical behavior of spatially inhomogeneous barrier height regions on silicon. Appl. Phys. Lett. 77, 2698–2700 (2000).

    CAS  Google Scholar 

  26. 26.

    Oener, S. Z. et al. Charge carrier-selective contacts for nanowire solar cells. Nat. Commun. 9, 3248 (2018).

    Google Scholar 

  27. 27.

    Burke, M. S., Enman, L. J., Batchellor, A. S., Zou, S. H. & Boettcher, S. W. Oxygen evolution reaction electrocatalysis on transition metal oxides and (oxy)hydroxides: activity trends and design principles. Chem. Mater. 27, 7549–7558 (2015).

    CAS  Google Scholar 

  28. 28.

    Li, S. Y. et al. Enhancing the photovoltage of Ni/n-Si photoanode for water oxidation through a rapid thermal process. ACS Appl. Mater. Interfaces 10, 8594–8598 (2018).

    CAS  Google Scholar 

  29. 29.

    Nellist, M. R. et al. Atomic force microscopy with nanoelectrode tips for high resolution electrochemical, nanoadhesion and nanoelectrical imaging. Nanotechnology 28, 095711 (2017).

    Google Scholar 

  30. 30.

    Tung, R. T. Recent advances in Schottky barrier concepts. Mater. Sci. Eng. R Rep. 35, 1–138 (2001).

    Google Scholar 

  31. 31.

    Lin, F. D. & Boettcher, S. W. Adaptive semiconductor/electrocatalyst junctions in water-splitting photoanodes. Nat. Mater. 13, 81–86 (2014).

    CAS  Google Scholar 

  32. 32.

    Nellist, M. R., Laskowski, F. A. L., Lin, F. D., Mills, T. J. & Boettcher, S. W. Semiconductor-electrocatalyst interfaces: theory, experiment, and applications in photoelectrochemical water splitting. Acc. Chem. Res. 49, 733–740 (2016).

    CAS  Google Scholar 

  33. 33.

    Digdaya, I. A., Adhyaksa, G. W. P., Trzesniewski, B. J., Garnett, E. C. & Smith, W. A. Interfacial engineering of metal-insulator-semiconductor junctions for efficient and stable photoelectrochemical water oxidation. Nat. Commun. 8, 15968 (2017).

    CAS  Google Scholar 

  34. 34.

    Ratcliff, E. L. et al. Evidence for near-surface NiOOH species in solution-processed NiOx selective interlayer materials: impact on energetics and the performance of polymer bulk heterojunction photovoltaics. Chem. Mater. 23, 4988–5000 (2011).

    CAS  Google Scholar 

  35. 35.

    Röppischer, H., Bumai, Y. A. & Feldmann, B. Flatband potential studies at the n‐Si/electrolyte interface by electroreflectance and C‐V measurements. J. Electrochem. Soc. 142, 650–655 (1995).

    Google Scholar 

  36. 36.

    Xu, G. Z. et al. Silicon photoanodes partially covered by Ni@Ni(OH)2 core-shell particles for photoelectrochemical water oxidation. ChemSusChem 10, 2897–2903 (2017).

    CAS  Google Scholar 

  37. 37.

    Lee, S. A. et al. Tailored NiOx/Ni cocatalysts on silicon for highly efficient water splitting photoanodes via pulsed electrodeposition. ACS Catal. 8, 7261–7269 (2018).

    CAS  Google Scholar 

  38. 38.

    Choi, K., Kim, K., Moon, I. K., Oh, I. & Oh, J. Evaluation of electroless Pt deposition and electron beam Pt evaporation on p-GaAs as a photocathode for hydrogen evolution. ACS. Appl. Energy Mater. 2, 770–776 (2019).

    CAS  Google Scholar 

  39. 39.

    Zhang, H. X. et al. A p-Si/NiCoSex core/shell nanopillar array photocathode for enhanced photoelectrochemical hydrogen production. Energy Environ. Sci. 9, 3113–3119 (2016).

    CAS  Google Scholar 

  40. 40.

    Wang, N., Tachikawa, T. & Majima, T. Single-molecule, single-particle observation of size-dependent photocatalytic activity in Au/TiO2 nanocomposites. Chem. Sci. 2, 891–900 (2011).

    CAS  Google Scholar 

  41. 41.

    Yoshikawa, K. et al. Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26%. Nat. Energy 2, 17032 (2017).

    CAS  Google Scholar 

  42. 42.

    Hu, S. et al. Thin-film materials for the protection of semiconducting photoelectrodes in solar-fuel generators. J. Phys. Chem. C 119, 24201–24228 (2015).

    CAS  Google Scholar 

  43. 43.

    Takata, T. & Domen, K. Particulate photocatalysts for water splitting: recent advances and future prospects. ACS Energy Lett. 4, 542–549 (2019).

    CAS  Google Scholar 

  44. 44.

    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).

    CAS  Google Scholar 

  45. 45.

    Su, Y. D. et al. Single-nanowire photoelectrochemistry. Nat. Nanotechnol. 11, 609–612 (2016).

    CAS  Google Scholar 

  46. 46.

    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).

    Google Scholar 

  47. 47.

    Litster, S. & McLean, G. PEM fuel cell electrodes. J. Power Sources 130, 61–76 (2004).

    CAS  Google Scholar 

  48. 48.

    Takahashi, Y. et al. Nanoscale visualization of redox activity at lithium-ion battery cathodes. Nat. Commun. 5, 5420 (2014).

    Google Scholar 

  49. 49.

    Marliere, C. & Dhahri, S. An in vivo study of electrical charge distribution on the bacterial cell wall by atomic force microscopy in vibrating force mode. Nanoscale 7, 8843–8857 (2015).

    CAS  Google Scholar 

  50. 50.

    Pfreundschuh, M., Hensen, U. & Muller, D. J. Quantitative imaging of the electrostatic field and potential generated by a transmembrane protein pore at subnanometer resolution. Nano Lett. 13, 5585–5593 (2013).

    CAS  Google Scholar 

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Acknowledgements

This work was funded by the Department of Energy, Basic Energy Sciences (award no. DE-SC0014279). F.A.L.L. acknowledges support from a NSF graduate research fellowship (no. 1309047). S.Z.O. acknowledges support from a research fellowship of the German Research Foundation (Deutsche Forschungsgemeinschaft, under project no. 408246589 (OE 710/1-1)). The atomic force microscope was purchased using funds provided by the NSF Major Research Instrumentation Program (grant no. DMR-1532225). We acknowledge use of shared instrumentation in the Center for Advanced Materials Characterization in Oregon and Rapid Materials Prototyping facilities, which are supported by grants from the M.J. Murdock Charitable Trust, the W.M. Keck Foundation, Oregon Nanoscience and Microtechnologies Institute and the National Science Foundation.

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F.A.L.L. and S.W.B. conceived the experiments and led the project. F.A.L.L. conducted the analytical modelling/coding and the dual-working-electrode experiments. F.A.L.L. and M.R.N. performed the operando photoelectrochemical experiments. F.A.L.L., A.M.G., D.C.B. and J.L.F. prepared photoelectrodes and conducted the ex situ AFM experiments. S.Z.O. was responsible for cross-sectional scanning electron microscope (SEM) analysis and contributed significantly to analysis of diode properties from conductive AFM data. F.A.L.L. and S.W.B. wrote the manuscript with input from all authors.

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Correspondence to Shannon W. Boettcher.

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Supplementary Table, Sections 1–11, Figs. 1–17 and Refs. 1–6

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Laskowski, F.A.L., Oener, S.Z., Nellist, M.R. et al. Nanoscale semiconductor/catalyst interfaces in photoelectrochemistry. Nat. Mater. 19, 69–76 (2020). https://doi.org/10.1038/s41563-019-0488-z

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