A synthetic mini-protein is reported that electrocatalytically reduces protons to hydrogen (H2) in water at pH 6.5 under aerobic conditions. Cobalt mimochrome VI*a (CoMC6*a) is a synthetic mini-protein with a cobalt deuteroporphyrin active site within a scaffold of two peptides, each of which is covalently bound to the cobalt deuteroporphyrin through an amide bond between a peptide lysine chain and a porphyrin propionic acid moiety. Comparison of the activity of CoMC6*a to that of cobalt-microperoxidase-11 (CoMP11-Ac), a cobalt porphyrin catalyst with a single proximal peptide and no organized secondary structure, reveals that CoMC6*a has significantly enhanced longevity, yielding a turnover number exceeding 230,000, in comparison to 25,000 for CoMP11-Ac. Bulk electrolysis performed with unpurified Genesee River water yields faradaic efficiencies (FE) that are similar to FEs performed in purified water, demonstrating that CoMC6*a is a robust catalyst. Furthermore, comparison of cyclic voltammograms of CoMC6*a and CoMP11-Ac indicates that the trifluoroethanol-induced folding of CoMC6*a lowers the overpotential for catalytic H2 evolution by up to 100 mV. These results demonstrate that even a minimal polypeptide matrix can enhance longevity and efficiency of a H2-evolution catalyst, providing insight for the development of bio-inspired catalysts for energy conversion.

Electrocatalytic H2 evolution in water by co-mimochrome VI*a, a synthetic mini-protein

2019 Fall National Meeting

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