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Mechanistic study of an immobilized molecular electrocatalyst by in situ gap-plasmon-assisted spectro-electrochemistry

Nature Catalysis volume 4, pages 157–163 (2021)Cite this article

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Abstract

Immobilized first-row transition metal complexes are potential low-cost electrocatalysts for selective CO2 conversion in the production of renewable fuels. Mechanistic understanding of their function is vital for the development of next-generation catalysts, although the poor surface sensitivity of many techniques makes this challenging. Here, a nickel bis(terpyridine) complex is introduced as a CO2 reduction electrocatalyst in a unique electrode geometry, sandwiched by thiol-anchoring moieties between two gold surfaces. Gap-plasmon-assisted surface-enhanced Raman scattering spectroscopy coupled with density functional theory calculations reveals that the nature of the anchoring group plays a pivotal role in the catalytic mechanism. Our in situ spectro-electrochemical measurement enables the detection of as few as eight molecules undergoing redox transformations in individual plasmonic hotspots, together with the calibration of electrical fields via vibrational Stark effects. This advance allows rapid exploration of non-resonant redox reactions at the few-molecule level and provides scope for future mechanistic studies of single molecules.

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Fig. 1: Electric field calibration in NPoM.
Fig. 2: Dark-field scattering spectroscopy and electrochemistry for Ni(tpyS)2.
Fig. 3: SERS and DFT calculations for Ni(tpyS)2.
Fig. 4: Ni(tpyS)2-catalysed CO2 reduction.

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Data availability

The data that support the findings of this study are available from the University of Cambridge data repository at https://doi.org/10.17863/CAM.60379.

Code availability

The code for spectral matching using the earth mover algorithm is available from the University of Cambridge data repository at https://doi.org/10.17863/CAM.60379.

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Acknowledgements

We thank G. Di Martino for support with spectro-electrochemical cell design, B. de Nijs for support with Raman facilities and D.-B. Grys for support with understanding of polarized and unpolarized DFT. We acknowledge funding from the EPSRC (nos. EP/L027151/1 and EP/R013012/1) and Cambridge NanoDTC (no. EP/L015978/1 to D.W. and C.R.), and the ERC (no. 757850 BioNet to D.B. and T.F.). We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (no. EP/P020194/1). We acknowledge use of the research computing facility (Rosalind) at King’s College London (https://rosalind.kcl.ac.uk).

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Author notes

  1. These authors contributed equally: Demelza Wright, Qianqi Lin.

Authors and Affiliations

  1. Nanophotonics Centre, Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, UK

    Demelza Wright, Qianqi Lin, Jack Griffiths, Charlie Readman & Jeremy J. Baumberg

  2. Department of Chemistry, University of Cambridge, Cambridge, UK

    Demelza Wright, Andreas Wagner & Erwin Reisner

  3. Department of Chemistry, King’s College London, London, UK

    Dénes Berta, Tamás Földes & Edina Rosta

  4. Department of Physics and Astronomy, University College London, London, UK

    Dénes Berta, Tamás Földes & Edina Rosta

  5. Melville Laboratory for Polymer Synthesis, Department of Chemistry, University of Cambridge, Cambridge, UK

    Charlie Readman

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Contributions

D.W., Q.L., E. Reisner and J.J.B. conceived the research and developed the experiments. D.B., T.F. and E. Rosta carried out DFT calculations and provided input on catalytic interpretation. A.W. and E. Reisner provided input on interpretation of electrochemical and catalytic results. J.G. helped with spectral analysis. C.R. helped with synthesis of Ni(tpyS)2. D.W., Q.L., D.B., T.F. and J.J.B. analysed the data and wrote the manuscript with input from all authors.

Corresponding authors

Correspondence to Edina Rosta, Erwin Reisner or Jeremy J. Baumberg.

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Peer review information Nature Catalysis thanks Irina Chernyshova and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–16, Tables 1–5 and Notes 1–7.

Supplementary Data

Atomic coordinates of the optimized molecules.

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Wright, D., Lin, Q., Berta, D. et al. Mechanistic study of an immobilized molecular electrocatalyst by in situ gap-plasmon-assisted spectro-electrochemistry. Nat Catal 4, 157–163 (2021). https://doi.org/10.1038/s41929-020-00566-x

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