The Influence of Surface Interactions on the Reversibility of Ferri/Ferrocyanide at Boron‐Doped Diamond Thin‐Film Electrodes

The electrochemistry of four redox analytes and methyl viologen, was investigated at polycrystalline, boron‐doped diamond thin‐film electrodes before and after anodic polarization and hydrogen plasma treatment. The as‐deposited diamond surface is predominantly hydrogen terminated, and quasi‐reversible cyclic voltammograms were observed for all of these couples at 0.1 V/s. After anodic polarization in , the surface atomic O/C ratio, as determined by X‐ray photoelectron spectroscopy, increased from 0.02 to ca. 0.20. Concomitant with the increase in surface oxygen, the for increased to over 200 mV, while the values for the other redox systems remained relatively unchanged. After acid washing and rehydrogenating the surface in a hydrogen plasma ( i.e., atomic hydrogen), the for returned to ca. 80 mV, while the values for the other three redox analytes remained close to the original values. The results demonstrate that electron transfer for ferri/ferrocyanide is very sensitive to the presence of surface carbon‐oxygen functionalities and that the electron transfer involves a site associated with the hydrogen‐terminated surface. The results also unequivocally rule out the influence of adventitious nondiamond carbon phases as the sole sites for the electron transfer. © 1999 The Electrochemical Society. All rights reserved.