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Cobalt Metallopeptide Electrocatalyst for the Selective Reduction of Nitrite to Ammonium

2018-12-12
Guo, Yixing
Stroka, Jesse R.
Kandemir, Banu
Dickerson, Claire E.
Bren, Kara L.
A cobalt-tripeptide complex (CoGGH) is developed as an electrocatalyst for the selective six-electron, eight-proton reduction of nitrite to ammonium in aqueous buffer near neutral pH. The onset potential for nitrite reduction occurs at -0.65 V vs Ag/AgCl (1 M KCl). Controlled potential electrolysis at -0.90 V generates ammonium with a faradaic efficiency of 90 +/- 3% and a turnover number of 3550 +/- 420 over 5.5 h. CoGGH also catalyzes the reduction of the proposed intermediates nitric oxide and hydroxylamine to ammonium. These results reveal that a simple metallopeptide is an active functional mimic of the complex enzymes cytochrome c nitrite reductase and siroheme-containing nitrite reductase.