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Catalyst self-assembly accelerates bimetallic light-driven electrocatalytic H2 evolution in water

Nature Chemistry (2024)Cite this article

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Abstract

Hydrogen evolution is an important fuel-generating reaction that has been subject to mechanistic debate about the roles of monometallic and bimetallic pathways. The molecular iridium catalysts in this study undergo photoelectrochemical dihydrogen (H2) evolution via a bimolecular mechanism, providing an opportunity to understand the factors that promote bimetallic H–H coupling. Covalently tethered diiridium catalysts evolve H2 from neutral water faster than monometallic catalysts, even at lower overpotential. The unexpected origin of this improvement is non-covalent supramolecular self-assembly into nanoscale aggregates that efficiently harvest light and form H–H bonds. Monometallic catalysts containing long-chain alkane substituents leverage the self-assembly to evolve H2 from neutral water at low overpotential and with rates close to the expected maximum for this light-driven water splitting reaction. Design parameters for holding multiple catalytic sites in close proximity and tuning catalyst microenvironments emerge from this work.

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Fig. 1: Mechanisms of H2 evolution.
Fig. 2: Synthesis of iridium complexes.
Fig. 3: Photoelectrocatalysis with diiridium complexes.
Fig. 4: Self-assembly into catalytic aggregates.
Fig. 5: Electrochemistry, photoelectrocatalysis and aggregation characterization of monometallic self-aggregating catalysts as compared to other catalysts in this study.
Fig. 6: Photoelectrocatalysis activity and overpotential relationships.

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All data generated and analysed in this study are included in this article and its Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under award DE-SC0014255 (principal investigator, A.J.M.M.). The NMR spectroscopy was supported by the National Science Foundation under grant CHE-1828183. The mass spectrometry was supported by the National Science Foundation under grant CHE-1726291. We acknowledge N. Kumarage for assistance with NMR spectral acquisition. We also acknowledge A. Tripathy, Director of the Macromolecular Interactions Facility where the DLS experiments were performed, for experimental assistance. The DLS experimental work was supported by the National Cancer Institute of the National Institutes of Health under award number P30CA016086. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We acknowledge A. Kumbhar for assistance with TEM imaging. The TEM work was performed at the Chapel Hill Analytical and Nanofabrication Laboratory, CHANL, a member of the North Carolina Research Triangle Nanotechnology Network, RTNN, which is supported by the National Science Foundation, grant ECCS-1542015, as part of the National Nanotechnology Coordinated Infrastructure, NNCI.

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  1. Tianfei Liu

    Present address: State Key Laboratory of Elemento-organic Chemistry, College of Chemistry, Nankai University, Tianjin, China

Authors and Affiliations

  1. Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    Isaac N. Cloward, Tianfei Liu, Jamie Rose, Tamara Jurado, Annabell G. Bonn, Matthew B. Chambers, Catherine L. Pitman, Marc A. ter Horst & Alexander J. M. Miller

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Contributions

T.L., J.R., A.G.B., M.B.C., C.L.P. and T.J. synthesized and characterized the iridium catalysts. I.N.C., T.L. and A.G.B. performed the CV studies. I.N.C., T.L., J.R. and T.J. conducted the CA and CPE studies. I.N.C., T.L. and M.A.t.H. analysed the catalyst aggregates using light scattering and NMR methods. A.J.M.M. conceived of the idea, directed the project and supervised the experimental design, execution and interpretation. I.N.C., T.L. and A.J.M.M. wrote the paper. All authors discussed the results and commented on the paper.

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Correspondence to Alexander J. M. Miller.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–134 and Tables 1–4.

Supplementary Data 1

CA source data.

Supplementary Data 2

CV source data.

Supplementary Data 3

DLS source data.

Supplementary Data 4

UV–visible spectroscopy source data.

Source data

Source Data Fig. 3

CV and CA data.

Source Data Fig. 4

DLS data.

Source Data Fig. 5

CV and DLS data.

Source Data Fig. 6

CA source data.

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Cloward, I.N., Liu, T., Rose, J. et al. Catalyst self-assembly accelerates bimetallic light-driven electrocatalytic H2 evolution in water. Nat. Chem. (2024). https://doi.org/10.1038/s41557-024-01483-3

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