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@INPROCEEDINGS{Jovanovic:1010210,
author = {Jovanovic, Sven and Jakes, Peter and Merz, Steffen and
Eichel, Rüdiger-A. and Granwehr, Josef},
title = {$\<i\>{I}n$ $operando\</i\>$ {NMR} investigations of
electrolyte chemistry during ${CO}\<sub\>2\</sub\>$
electrolysis},
reportid = {FZJ-2023-03019},
year = {2023},
abstract = {The electrolytic reduction of CO2 in aqueous media is a
powerful method for the large scale utilization of carbon
dioxide. There have been large advances in catalyst and cell
design, but only little progress has been made regarding in
operando and in situ methods for the research of chemical
and physical processes taking during electrolysis. NMR
spectroscopy is a powerful method for the investigation of
chemical systems, and has been applied regularly for the
study of catalytically reactions. In general, NMR is thought
to be incompatible with electrochemical reactors, i.e.
electrolysis cells, due to the distortion of the main
magnetic and radio frequency field by conductive cell
components. In this study, we overcame these challenges and
developed an in operando electrolysis setup which enables
NMR investigations of the electrolytic CO2 reduction, which
is compatible with standard hardware and pulse sequences.
The setup was applied to the examination of physical and
chemical properties of solvated CO2 and a commonly used
bicarbonate salt electrolyte during three electrochemical
stages with increasingly negative potential. In addition to
acquiring 13C NMR spectra over course of the electrolysis,
T1 and T2 relaxation as well as 1D exchange spectroscopy
(EXSY) experiments were utilized in order to learn about the
dynamics and equilibrium reactions of the involved species.
It was found that in a concentrated electrolyte solution,
the electrolyte anions and cations exist both as free ions
and ion pairs, where the exchange rate between both forms
decreases with increasingly negative potential. The effect
of the potential on the exchange rate was confirmed by
repeating the experiments at different magnetic field
strengths. Furthermore, it was shown via analysis of the
relaxation data that solvated CO2 is preferentially in a
dynamic equilibrium with bicarbonate anions in form of an
ion pair, and that the CO2/bicarbonate equilibrium reaction
rate increases with increasingly stable ion pairs in
solution. Finally, a catalytic mechanism was proposed on
this basis, where the electrolyte cation stabilizes the
transition of bicarbonate to CO2 comparable to the enzyme
carbonic anhydrase in biological systems.},
month = {Jun},
date = {2023-06-25},
organization = {20th International Conference on
Carbon Dioxide Utilization, Bari
(Italy), 25 Jun 2023 - 30 Jun 2023},
subtyp = {Plenary/Keynote},
cin = {IEK-9},
cid = {I:(DE-Juel1)IEK-9-20110218},
pnm = {1232 - Power-based Fuels and Chemicals (POF4-123) / DFG
project 390919832 - EXC 2186: Das Fuel Science Center –
Adaptive Umwandlungssysteme für erneuerbare Energie- und
Kohlenstoffquellen (390919832)},
pid = {G:(DE-HGF)POF4-1232 / G:(GEPRIS)390919832},
typ = {PUB:(DE-HGF)6},
doi = {10.34734/FZJ-2023-03019},
url = {https://juser.fz-juelich.de/record/1010210},
}