In situ ATR-IR study of Fe(CN)63-/Fe(CN)64- redox system on boron-doped diamond electrode

Hexacyanoferrate redox couple is extensively used as a benchmark to evaluate electrode activity in aqueous electrochemistry. Interestingly, boron-doped diamond (BDD) electrode shows surface-dependent behaviors: fast electron transfer rate on hydrogen terminated surface and slow rate on oxygen terminated surface. On the other hand, origin of the surface-dependent response still remains unclear. In this study, we spectroscopically investigated the determinants of electrochemical activity of this system using in situ ATR-IR technique. Our experiment revealed that adsorbed intermediate species of this redox system exist on the hydrogen terminated BDD. On the oxygen terminated BDD, the bands of adsorbed species were weakened, indicating that the oxygen functional groups specifically inhibited the adsorption of the intermediate species.