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Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis
Published on: January 6, 2016
Hydrogen-terminated diamond electrodes. II. Redox activity
Wenying Zhang1, Jürgen Ristein, Lothar Ley
1Technical Physics, University of Erlangen, Germany.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|November 13, 2008
Summary
Diamond's spontaneous p-type conductivity arises from electrochemical charge transfer. This study provides direct evidence of diamond surface redox activity, revealing a mixed potential under open circuit conditions.
Area of Science:
- Materials Science
- Electrochemistry
- Surface Chemistry
Background:
- Diamond exhibits robust p-type surface conductivity spontaneously under atmospheric conditions.
- Hydrogen-termination of diamond surfaces is crucial for this conductivity.
- Electrochemical charge transfer with airborne redox couples is hypothesized to cause surface holes.
Purpose of the Study:
- To provide direct experimental proof of the redox activity of the diamond surface.
- To investigate the influence of pH on the electrochemical behavior of hydrogen-terminated diamond.
- To characterize the redox processes occurring at the diamond-electrolyte interface.
Main Methods:
- Measurement of pH-dependent open circuit potentials on diamond electrodes.
- Quasistatic polarization curves for hydrogen-terminated and partially oxidized diamond.
- Analysis of mixed (corrosion) potentials under open circuit conditions.
Main Results:
- Direct evidence for redox activity of the diamond surface was obtained.
- A mixed potential, consistent with simultaneous equilibration of hydrogen-hydronium and oxygen-hydroxyl redox couples, was observed.
- Extremely long time constants and low exchange current densities were measured for the redox equilibrium.
Conclusions:
- The spontaneous p-type conductivity of hydrogen-terminated diamond is linked to redox processes at the surface.
- The diamond surface acts as an electrode in contact with multiple redox couples.
- Characterizing these slow redox processes requires specialized experimental approaches.
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