Porous boron-doped diamond electrodes fabricated via two-step thermal treatment

A two-step thermal treatment method was developed for the fabrication of porous conductive boron-doped diamond (BDD) electrodes. The first step involved graphitization of the BDD thin film surface to form a fine microstructure by heating in an argon atmosphere at 1000 °C. The second step was removal of the graphitic components by oxidation in air at 425 °C. The heat treatment resulted in the formation of dense pores with several tens to several hundred nanometer sizes or smaller on the BDD surface. The pore formation mechanism was discussed by microscopic observation of the (1 1 1) and (1 0 0) crystal facets on the treated BDD surface. The porous BDD electrode exhibited a double-layer capacitance (Cdl) of ca. 140 μF cm−2, which was estimated from cyclic voltammetry (CV) and galvanostatic measurements in an aqueous electrolyte. This Cdl value was approximately 40 times larger than that for the as-deposited BDD electrode, while the potential window remained wide at ca. 3 V.