In order to produce polycrystalline oxygen-terminated boron-doped diamond (BDD) electrodes suitable for electroanalysis (i.e., widest solvent window, lowest capacitive currents, stable and reproducible current responses, and capable of demonstrating fast electron transfer) for outer sphere redox couples, the following factors must be considered. The material must contain enough boron that the electrode shows metal-like conductivity; electrical measurements demonstrate that this is achieved at [B] > 10(20) B atoms cm(-3). Even though BDD contains a lower density of states than a metal, it is not necessary to use extreme doping levels to achieve fast heterogeneous electron transfer (HET). An average [B] ~ 3 × 10(20) B atoms cm(-3) was found to be optimal; increasing [B] results in higher capacitive values and increases the likelihood of nondiamond carbon (NDC) incorporation. Hydrogen-termination causes a semiconducting BDD electrode to behave metal-like due to the additional surface conductivity hydrogen termination brings. Thus, unless [B] of the material is known, the electrical properties of the electrode may be incorrectly interpreted. Note, this layer (formed on a lapped electrode) is electrochemically unstable, an effect which is exacerbated at increased potentials. It is essential during growth that NDC is minimized as it acts to increase capacitive currents and decrease the solvent window. We found complete removal of NDC after growth using aggressive acid cleans, acid cycling, and diamond polishing impossible. Although hydrogen termination can mask the NDC signature in the solvent window and lower capacitive currents, this is not a practical procedure for improving sensitivity in electroanalysis. Finally, alumina polishing of lapped, NDC free, freestanding, BDD electrodes was found to be an effective way to produce well-defined, stable, and reproducible surfaces, which support fast (reversible) HET for Fe(CN)6(4-) electrolysis, the first time this has been reported at an oxygen-terminated surface.

Conducting carbon materials: A multi-microscopy approach shows that local heterogeneous electron-transfer rates at conducting diamond electrodes correlate with the local density of electronic states. This model of electroactivity is of considerable value for the rational design of conducting diamond electrochemical technologies, and also provides key general insights on electrode structure controls in electrochemical kinetics (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Leitfähige Kohlenstoffmaterialien: Eine Kombination von Mikroskopietechniken zeigt, dass die lokalen heterogenen Elektronentransferraten leitfähiger Diamant‐Elektroden mit der lokalen Dichte elektronischer Zustände korrelieren. Dieses Elektroaktivitätsmodell ist für die Entwicklung von elektrochemischen Methoden basierend auf leitfähigem Diamant bedeutsam und zeigt den Einfluss der Elektrodenstruktur auf die elektrochemische Kinetik (siehe Bild).