<p>High
pressure high temperature (HPHT) synthesis of crystallographically well-defined
boron doped diamond (BDD) microparticles, suitable for electrochemical
applications and using the lowest P and T (5.5 GPa and 1200°C) growth conditions to date, is reported. This is aided through the use
of a metal (Fe-Ni) carbide forming catalyst and an aluminum
dibromide (AlB<sub>2</sub>) boron source. The latter also acts as a nitrogen sequester, to reduce
boron-nitrogen charge compensation effects. Raman microscopy and electrochemical
measurements on individual microparticles reveal they are suitably doped to be
considered metallic-like and contain negligible sp<sup>2</sup> bonded carbon. A
compaction process is used to create macroscopic porous electrodes from the
BDD microparticles. Voltammetric analysis of the one-electron reduction of
Ru(NH<sub>3</sub>)<sub>6</sub><sup>3+</sup> reveals large capacitive and
resistive components to the current-voltage curves, originating from solution
trapped within the porous material. Scanning electrochemical cell microscopy
(SECCM) is employed to map the local electrochemical activity and porosity at
the micron scale. These electrodes retain the advantageous properties of polycrystalline
BDD grown by chemical vapor deposition, such as large aqueous solvent window
and resistance to corrosion, but with the additional benefits of a high, electrochemically
accessible, surface area. </p>
High Pressure High Temperature Synthesis of Highly Boron Doped Diamond Microparticles and Porous Electrodes for Electrochemical Applications
