Issue 19, 2020

Unraveling the mechanism of biomimetic hydrogen fuel production – a first principles molecular dynamics study

Abstract

The Fe2(bdt)(CO)6 [bdt = benzenedithiolato] complex, a synthetic mimic of the [FeFe] hydrogenase enzyme can electrochemically convert protons into molecular hydrogen. Molecular understanding of the cascade of reaction steps is important for the design of more efficient catalysts. In this study, we investigate the reaction mechanism of the hydrogen production catalysis in explicit solution of acetonitrile using first principles molecular dynamics simulations. We have characterized all reduction and protonation intermediates taking part in the catalytic cycle. Free energy surfaces of the activated reaction steps are calculated using metadynamics. We find that the second protonation leading to molecular hydrogen formation is the rate limiting step. Direct protonation of the bridging hydride by a proton from the solution to form H2 is the most favorable reaction pathway. However, also a bdt sulfur atom can become protonated, leading to a possible proton trap state that reduces the catalytic efficiency. Our calculations validate the ECEC mechanism proposed using cyclic voltammetry.

Graphical abstract: Unraveling the mechanism of biomimetic hydrogen fuel production – a first principles molecular dynamics study

Supplementary files

Article information

Article type
Paper
Submitted
16 Kax 2019
Accepted
10 Cig 2020
First published
10 Cig 2020
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2020,22, 10447-10454

Unraveling the mechanism of biomimetic hydrogen fuel production – a first principles molecular dynamics study

R. C. Puthenkalathil, M. Etinski and B. Ensing, Phys. Chem. Chem. Phys., 2020, 22, 10447 DOI: 10.1039/C9CP06770A

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