Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 17: Solid-Liquid Interfaces I: Reactions and Electrochemistry
O 17.6: Talk
Monday, March 16, 2020, 16:30–16:45, TRE Phy
Electrochemical N2 reduction: How nature does it & what we can learn from it — •Vanessa J. Bukas and Jens K. Nørskov — Department of Physics, Technical University of Denmark
Electrochemical conversion of molecular N2 into ammonia (NH3) is a key goal in our quest toward global sustainability. Catalyzing this reaction, however, faces the formidable task of breaking the stable N≡N bond, while simultaneously suppressing the parasitic hydrogen evolution reaction (HER). As a result, all attempts to realize such a technology have so far been hindered by invariably large (>1 V) overpotentials and low (∼1%) selectivity. Remarkably, the enzyme nitrogenase overcomes these limitations and selectively reduces atmospheric N2 under ambient conditions to provide NH3-based fertilizer directly into the soil. Guided by recent experimental evidence of a structurally dynamic cofactor [1], we present here a molecular-level mechanism of the biologic N2 fixation from first-principles calculations [2]. The proposed mechanism shows that the enzyme is catalytically activated/deactivated through site-specific ligand exchange in order to drive the most difficult steps of the reaction. In the meantime, rate-limiting electron transfer prevents the reaction from evolving via a series of coherently-coupled proton-electron transfers which, in turn, kinetically suppresses the competing HER. Based on this insight, we propose revised strategies for designing the next generation of solid catalysts for electrochemical NH3 production.
[1] Sippel et al., Science 359, 1484-1489 (2018)
[2] Bukas and Nørskov, ChemRxiv (2019)