Electrocatalytic reduction of carbon dioxide to carbon monoxide and methane at an immobilized cobalt protoporphyrin
Jing Shen1, Ruud Kortlever1, Recep Kas2, Yuvraj Y. Birdja1, Oscar Diaz-Morales1, Youngkook Kwon1, Isis Ledezma-Yanez1, Klaas Jan P. Schouten1,
Guido Mul2 & Marc T.M. Koper1
doi:10.1038/ncomms9177
Guido Mul2 & Marc T.M. Koper1
Nature Communications ARTICLE
Received 20 Mar 2015 | Accepted 27 Jul 2015 | Published 1 Sep 2015 DOI: 10.1038/ncomms9
Received 20 Mar 2015 | Accepted 27 Jul 2015 | Published 1 Sep 2015 DOI: 10.1038/ncomms9
Abstract
The electrochemical conversion of carbon dioxide and water into useful products is a major challenge in facilitating a closed carbon cycle. Here we report a cobalt protoporphyrin immobilized on a pyrolytic graphite electrode that reduces carbon dioxide in an aqueous acidic solution at relatively low overpotential (0.5 V), with an efficiency and selectivity comparable to the best porphyrin-based electrocatalyst in the literature. While carbon monoxide is the main reduction product, we also observe methane as by-product. The results of our detailed pH-dependent studies are explained consistently by a mechanism in which carbon dioxide is activated by the cobalt protoporphyrin through the stabilization of a radical intermediate, which acts as Brønsted base. The basic character of this intermediate explains how the carbon dioxide reduction circumvents a concerted proton–electron transfer mechanism, in contrast to hydrogen evolution. Our results and their mechanistic interpretations suggest strategies for designing improved catalysts.
http://www.nature.com/ncomms/2015/150901/ncomms9177/full/ncomms9177.html
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