Potential- and Buffer-Dependent Selectivity for the Conversion of CO(2) to CO by a Cobalt Porphyrin-Peptide Electrocatalyst in Water

[Image: see text] A semisynthetic electrocatalyst for carbon dioxide reduction to carbon monoxide in water is reported. Cobalt microperoxidase-11 (CoMP11-Ac) is shown to reduce CO(2) to CO with a turnover number of up to 32,000 and a selectivity of up to 88:5 CO:H(2). Higher selectivity for CO production is favored by a less cathodic applied potential and use of a higher pK(a) buffer. A mechanistic hypothesis is presented in which avoiding the formation and protonation of a formal Co(I) species favors CO production. These results demonstrate how tuning reaction conditions impact reactivity toward CO(2) reduction for a biocatalyst previously developed for H(2) production.