(A) Cartoon
representation of an enzymatic device for catalysis
of the water–gas shift reaction. Electrons released by CODH-catalyzed
CO oxidation are transferred through a graphite particle to a CO-tolerant
hydrogenase that reduces protons to H2. (B) Typical cyclic
voltammograms (from separate experiments) showing the reversibility
of electrocatalysis by CODHCh I and a
hydrogenase (Hyd-2) from E. coli, measured
at pH 6.0, 30 °C, scan rate 10 mV s–1, electrode
rotation rate 2500 rpm. (C) H2 production and CO depletion
over the course of 55 h at pH 6.0, 30 °C, as quantified by GC
analysis. Fresh aliquots of CO were introduced at the times indicated.
Adapted with permission from ref (51). Copyright 2009 American Chemical Society.