Characterization of the performance and failure mechanisms of boron-doped ultrananocrystalline diamond electrodes

This research investigated the anodic stability of boron-doped ultrananocrystalline diamond (BD-UNCD) film electrodes on a variety of substrates (Si, Ta, Nb, W, and Ti) at a current density of 1 A cm(-2). At an applied charge of 100 A h cm(-2), measurable BD-UNCD film wear was not observed using SEM cross-sectional measurements. However, anodic treatment of the electrodes resulted in surface oxidation and film delamination, which caused substantial changes to the electrochemical properties of the electrodes. The substrate roughness, substrate electroactivity, and compactness of the substrate oxide were key parameters that affected film adhesion, and the primary mechanism of electrode failure was delamination of the BD-UNCD film. Substrate materials whose oxides had a larger coefficient of thermal expansion relative to the reduced metal substrates resulted in film delamination. The approximate substrate stability followed the order of: Ta > Si > Nb > W a parts per thousand << Ti.