Hydrogen-terminated diamond electrodes. II. Redox activity.
One of the most attractive features of diamond is its robust p -type surface conductivity that develops spontaneously under atmospheric conditions on hydrogen-terminated samples. An electrochemical charge transfer between diamond and an air-borne redox couple has been suggested to be responsible for the spontaneous appearance of surface-near holes. We present direct proof for the redox activity of the diamond surface by measuring pH -dependent open circuit potentials and quasistatic polarization curves for hydrogen-terminated and partially oxidized diamond electrodes. Under open circuit conditions we find in fact a mixed (or corrosion) potential that is consistent with the simultaneous equilibriation of the electrode versus both the hydrogen-hydronium and the oxygen-hydroxyl redox couple. Our data show extremely long-time constants for establishing the redox equilibrium and very low exchange current densities making the identification and characterization of the redox process a demanding experimental task.
Zhang
Wenying
W
Technical Physics, University of Erlangen, Germany.
Ristein
Jürgen
J
Ley
Lothar
L