Speaker
Description
For carbon neutral transport as well as storage of excess energy, the conversion of atmospheric CO$_2$ into valuable fuels is a promising solution.$^1$ Methanol or ethanol are especially useful as fuels, since they can be easily purified and provide a high energy density when used in fuel cells for public transport.$^2$ The reaction pathway of the CO$_2$ electroreduction (CO$_2$RR) has already been extensively studied, but is still not clearly understood in its full complexity.$^{1,3}$ Small organic acids, i.e. formic or acetic acid, which are well-known products of the CO$_2$RR, are believed to not be further reduceable, which is rather not desirable. Here we present results on the electroreduction of these acids on Mo2C and Mo electrodes, where notable amounts of methanol or ethanol were formed. The results obtained with ex situ nuclear magnetic resonance (NMR) spectroscopy were further verified with online differential electrochemical mass spectrometry (DEMS), where exact reaction onsets could be determined. Interestingly, we find that formic and acetic acid readily form in humid CO$_2$ atmosphere Mo$_2$C and Mo. We realize that a thin native oxide layer is ubiquitous on these electrodes, which is the key factor for the activation of CO$_2$ and formic/acetic acid formation. Similar behavior has been reported for TiO$_2$.$^4$ With these results we can provide cutting-edge insights in the mechanistic understanding of the CO$_2$RR, since the reactivity of formic and acetic acid is exceptionally higher than believed and, hence, these molecules play an extraordinary role as intermediates in the most desirable alcohol formation pathway during the electroreduction of CO$_2$.
References:
[1] Nitopi, S. et al.; Chem. Rev. 2019, 119 (12) 7610-7672.
[2] Braunchweig, B. et al.; Catalysis Today 2013, 202, 197–209.
[3] Kortlever, R. et al.; J. Phys. Chem. Lett. 2015, 6 (20), 4073–4082.
[4] Balajka, J. et al.; Science 2018, 361, 786–789.
| Speaker Country | Austria |
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