Surface structure and electrochemical characteristics of boron-doped diamond exposed to rf N2-plasma

Epitaxial (100)-oriented diamond layer with boron doping above 1020 cm−3 was exposed to an RF N2 plasma, the resulting surface structure and electrochemical characteristics were investigated. The N2 plasma treatment was combined with in vacuo pre-heating to remove adsorbates and with surface shielding to reduce plasma-induced corrosion. X-ray photoemission spectroscopy revealed full nitrogenation of the surface with the presence of CN and CN bond structures. Anodic treatment in 0.1 M KOH in the oxygen evolution range generated nitrogen–oxygen bonds and carbon–oxygen functionalities which partially substitute the initial nitrogen-termination. The nitrogenated and electrochemically polarised diamond electrode exhibited higher catalytic activity to [Fe(CN)6]3−/4− but slower to [Ru(NH3)6]3+/2+ redox reactions, as compared to an identical diamond electrode with fully oxygen-terminated surface.

► CN and CN bond structures on diamond surface after exposure to RF N2 plasma.
► Partial oxidation of the N-terminated surface after anodic treatment in electrolytes.
► Higher activity to [Fe(CN)6]3−/4− reactions compared to fully oxygen-terminated surface.