Carbon-based materials are regarded as an environmentally benign alternative to the conventional metal electrode used in electrochemistry from the viewpoint of sustainable chemistry. Among various carbon electrode materials, boron-doped diamond (BDD) exhibits superior electrochemical properties. However, it is still uncertain how surface chemical species of BDD influence the electrochemical performance, because of the difficulty in characterizing the surface species. Here, we have developed in situ spectroscopic measurement systems on BDD electrodes, i.e., in situ attenuated total reflection infrared spectroscopy (ATR-IR) and electrochemical X-ray photoelectron spectroscopy (EC-XPS). ATR-IR studies at a controlled electrode potential confirmed selective surface hydroxylation. EC-XPS studies confirmed deprotonation of C–OH groups at the BDD/electrolyte interface. These findings should be important not only for better understanding of BDD’s fundamentals but also for a variety of applications.

Electrochemical surface oxidation in acidic solutions was investigated on a boron-doped diamond film electrode, fabricated on a silicon prism, using attenuated total reflection infrared spectroscopy. At positive potentials above +1.3 V (reversible hydrogen electrode, RHE), the bands of surface oxygen species appear at 1745 and 1250 cm–1. Since these bands exhibit no isotope shift in deuterium solution, they are assigned to the CO and C–O stretching modes, respectively. These bands have the maximum intensity at +3.3 V (RHE) and reversibly disappear around +0.9 V (RHE) in the potential step to the negative direction. The potentials at which the bands appear and disappear are identical to those of the anodic and cathodic peaks of the cyclic voltammogram, respectively.