Electrocatalysis for Fuel Cells at Enzyme-Modified Electrodes - Fuel Cell Catalysis: A Surface Science Approach - page 585

& CHAPTER 17
Electrocatalysis for Fuel Cells at
Enzyme-Modified Electrodes
K. A. VINCENT
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
S. C. BARTON
Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing,
MI 48824, USA
G. W. CANTERS
Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
H. A. HEERING
Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, 2628, CJ Delft,
The Netherlands; and Leiden Institute of Chemistry
17.1 INTRODUCTION
A number of reactions relevant to fuel cell catalysis are carried out under ambient
conditions by enzymes that employ catalytic centers comprising common metals or
organic cofactors (Fig. 17.1). One example is the efficient catalytic reduction of O 2
to H 2 O at copper centers in the fungal enzyme laccase. Another is the rapid and revers-
ible oxidation or production of H 2 by microbial hydrogenase enzymes that incorporate
catalytic centers comprising iron, or nickel and iron. These reactions are not limited to
microorganisms living in extreme environments: on the contrary, most fungi use lac-
cases to couple O 2 reduction to the oxidation of organic molecules, and hydrogen
cycling is integral to communities of bacteria in the human gut, in soil, and in water-
ways. Variation in amino acid residues around the active site as well as further away in
the protein provides scope for subtle alteration of the properties of the catalytic centers
in enzymes, and, over millions of years, microorganisms have evolved to carry out
energy cycling reactions selectively in complex environments. For example, a class