Water oxidation electrocatalysis using ruthenium coordination oligomers adsorbed on multiwalled carbon nanotubes


Photoelectrochemical cells that utilize water as a source of electrons are one of the most attractive solutions for the replacement of fossil fuels by clean and sustainable solar fuels. To achieve this, heterogeneous water oxidation catalysis needs to be mastered and properly understood. The search continues for a catalyst that is stable at the surface of electro(photo)anodes and can efficiently perform this reaction at the desired neutral pH. Here, we show how oligomeric Ru complexes can be anchored on the surfaces of graphitic materials through CH–π interactions between the auxiliary ligands bonded to Ru and the hexagonal rings of the graphitic surfaces, providing control of their molecular coverage. These hybrid molecular materials behave as molecular electroanodes that catalyse water oxidation to dioxygen at pH 7 with high current densities. This strategy for the anchoring of molecular catalysts on graphitic surfaces can potentially be extended to other transition metals and other catalytic reactions.

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Fig. 1: NMR characterization of the coordination oligomers.
Fig. 2: STM of 15 on HOPG.
Fig. 3: Oligomer–surface interaction by 2D GIWAXS.
Fig. 4: Theoretical analysis based on DFT/MM.
Fig. 5: XAS at the surface of the electrodes.
Fig. 6: Water oxidation electrocatalytic performance of 15@CNT@GC.

Data availability

All data generated during this study, experimental details together with additional, analytic, spectroscopic, electrochemical, X-ray scattering, microscopy and DFT data are included in this article or in the Supplementary Information. Data for Figs. 16 are available as source data with this paper. Data for Supplementary Figs. are available from the corresponding author on reasonable request.

The crystal data parameters of 1 and 2 and all information related to the structures can be found in the deposited CIF/Checkcif-files. CCDC 1945004 (1) and 1945005 (2) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures.

A data set collection of computational results is available as source data with this paper and can be accessed at ioChem-BD repository via https://doi.org/10.19061/iochem-bd-1-180. Source data are provided with this paper.


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Md.A.H. acknowledge funding from AGAUR with grant nos 2016FI_B 01011 and 2014 SGR-915. F.M. and A.d.A. acknowledge funding from MINECO (CTQ2017-87792-R). A.d.A. thanks MINECO for a FPI fellowship (BES-2015-073012). J.L. thanks the Alexander von Humboldt Foundation for financial support. D.M. acknowledges support by the Severo Ochoa Excellence programme (SEV-2016-0686) from the Instituto IMDEA Nanociencia, the Acciones de Dinamización “Europa Investigacion” grant (EIN2019-103399) and the Spanish Ministerio de Ciencia, Innovación y Universidades grant (PID2019-111086RA-I00). X.S. acknowledges funding from MINECO/FEDER (PID2019-104171RB-I00). A.L. acknowledges support from the Ministerio de Ciencia e Innovación, FEDER and AGAUR through grants: PID2019-111617RB-I00 and 2017-SGR-1631. XAS experiments were performed at the CLAESS beamline at the ALBA Synchrotron under proposal No. 2016091818 and 2017092493 with the collaboration of ALBA staff and additionally used resources of the sector 20 beamline at the APS at Argonne National Laboratory. Sector 20 beamline at APS is operated by the US DOE (Contract No. DE-AC02-06CH11357) and the Canadian Light Source. Synchrotron X-ray scattering experiments were performed at NCD-SWEET beamline at the ALBA synchrotron with the collaboration of ALBA staff (Proposal 2020014050).

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Md.A.H. and M.G.-S. performed the synthesis, characterization and electrochemical experiments and coordinated the tasks with all authors. These authors contributed equally to this work. J.A.A.W.E. performed the STM experiments. D.M. performed the XANES and EXAFS measurements and data analysis. Y.S. prepared the samples for XANES and EXAFS experiments. J.B.-B. performed the single crystal X-ray structure determinations. M.M. and E.S. performed and analysed the synchrotron scattering experiments. J.L., A.G.-M. and C.S. designed, carried out and analysed electron microscopy experiments. F.M. designed the computational part. A.d.A. performed the theoretical calculations. C.G.-S. supervised the project. A.L. conceived the idea of the project and wrote the paper with input from other authors. All authors contributed to the design of experiments, analysis of the results and preparation of the manuscript.

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Correspondence to Mario Lanza or Feliu Maseras or Carolina Gimbert-Suriñach or Antoni Llobet.

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Supplementary methods, Figs. 1–48, computational methods.

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Hoque, M.A., Gil-Sepulcre, M., de Aguirre, A. et al. Water oxidation electrocatalysis using ruthenium coordination oligomers adsorbed on multiwalled carbon nanotubes. Nat. Chem. 12, 1060–1066 (2020). https://doi.org/10.1038/s41557-020-0548-7

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