CO2 reduction off base

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Science  24 Feb 2017:
Vol. 355, Issue 6327, pp. 809-810
DOI: 10.1126/science.355.6327.809-f

The electrochemical reduction of CO2 can yield a range of products, including aldehydes, acids, and alcohols, as well as hydrogen formed by the competing hydrogen evolution reaction (HER) at the high cathodic potentials used. Birdja and Koper show in studies with boron-doped diamond electrodes that aldehydes are the direct product of CO2 reduction and that primary alcohols and carboxylic acids form through Cannizzaro-type disproportionation (thus, methanol and formic acid form from formaldehyde). These reactions are unexpected because they require base, but the HER creates OH− as a by-product, so regions near the electrode can be at high pH. Such reactions are inhibited in buffered electrolytes, which the authors recommend to sort out direct and indirect product formation mechanisms.

J. Am. Chem. Soc. 10.1021/jacs.6b12008 (2016).

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