Investigations of the Efficient Electrocatalytic Interconversions of Carbon Dioxide and Carbon Monoxide by Nickel-Containing Carbon Monoxide Dehydrogenases - The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment - page 93

attached to PGE, CdS thin film and TiO 2 thin film electrodes are shown in Figure 13 .
In contrast to the result observed for PGE, only CO 2 reduction is observed at CdS
and TiO 2 .
The experiments demonstrate how to rectify reversible electrocatalysts for the
fuel-forming direction since the most efficient catalysts for solar fuel production
should operate close to reversible potentials [ 63 ].

7 Conclusions

The linear CO 2 molecule is difficult to reduce, but enzymes provide a superb
example of how this chemistry has been perfected by evolution. The active site of
CODH reveals simple tricks that could be mimicked by chemists, although it is
going to be challenging to synthesize the precise, outer-shell environment that
nature so easily rolls out during transcription. Protein film electrochemistry has
proved to be a valuable tool for separating the different reactions as a smooth
function of potential, as it has been demonstrated for hydrogenases. The PFE results
have yielded important information - in the 'potential domain' - to complement
and clarify the picture built up from structure and spectroscopy.

Abbreviations

acetyl-CoA acetyl-coenzyme A

ACDS acetyl-CoA decarbonylase synthase

Ch Carboxydothermus hydrogenoformans

CoA coenzyme A

CODH carbon monoxide dehydrogenase

CODH/ACS carbon monoxide dehydrogenase/acetyl-CoA synthase

CoFeSP corrinoid-iron-sulfur protein

E FB flatband potential

EPR electron paramagnetic resonance

Mb Methanosarcina barkeri

MES 2-(N-morpholino)ethanesulfonic acid

Mt Moorella thermoacetica

PDB Protein Data Base

PFE protein film electrochemistry

PGE pyrolytic graphite edge

Rr Rhodospirillum rubrum

SHE standard hydrogen electrode

XAS X-ray absorption spectroscopy