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Electrocatalytic metal hydride generation using CPET mediators


Transition metal hydrides (M-H) are ubiquitous intermediates in a wide range of enzymatic processes and catalytic reactions, playing a central role in H+/H2 interconversion1, the reduction of CO2 to formic acid (HCOOH)2 and in hydrogenation reactions. The facile formation of M-H is a critical challenge to address to further improve the energy efficiency of these reactions. Specifically, the easy electrochemical generation of M-H using mild proton sources is key to enable high selectivity versus competitive CO and H2 formation in the CO2 electroreduction to HCOOH, the highest value-added CO2 reduction product3. Here we introduce a strategy for electrocatalytic M-H generation using concerted proton–electron transfer (CPET) mediators. As a proof of principle, the combination of a series of CPET mediators with the CO2 electroreduction catalyst [MnI(bpy)(CO)3Br] (bpy = 2,2′-bipyridine) was investigated, probing the reversal of the product selectivity from CO to HCOOH to evaluate the efficiency of the manganese hydride (Mn-H) generation step. We demonstrate the formation of the Mn-H species by in situ spectroscopic techniques and determine the thermodynamic boundary conditions for this mechanism to occur. A synthetic iron–sulfur cluster is identified as the best CPET mediator for the system, enabling the preparation of a benchmark catalytic system for HCOOH generation.

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Fig. 1: CPET-mediated metal hydride formation.
Fig. 2: Catalytic activity and spectroscopic characterization of relevant intermediates of CPET-mediated CO2RR activity of MnI-cat.
Fig. 3: Thermodynamic and kinetic considerations for catalytic CPET-mediated metal hydride formation.
Fig. 4: CO2RR activity of MnI-cat in the presence of various CPET mediators.

Data availability

The data that support the findings of this study (catalytic activity tests, cyclic voltammograms, NMR, UV–Vis and IRSEC spectra) are available within the paper and its Supplementary Information files.


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We thank L. Grunwald and A. Mouchfiq for technical assistance and preliminary studies, and R. Verel for assistance with NMR studies. We acknowledge funding from Agence Nationale pour la Recherche, ANR Jeune Chercheur-Jeune Chercheuse ANR-17-CE05-0021 (S.D., V.M.); European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 853064 (S.D., F.M., V.M.)); and Swiss National Science Foundation (SNSF) project funding (grant no. 200021_197153 / 1 (V.M.)).

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Authors and Affiliations



S.D. and V.M. conceptualized the study and were responsible for the methodology. S.D., F.M. and E.B. undertook the investigations. V.M. was responsible for funding acquisition and supervision. M.F. and V.M. administered the project. S.D., F.M. and V.M. wrote the original draft. All authors reviewed and edited the manuscript.

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Correspondence to Victor Mougel.

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Dey, S., Masero, F., Brack, E. et al. Electrocatalytic metal hydride generation using CPET mediators. Nature 607, 499–506 (2022).

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