Kazuki Arihara

Electrochemical Production of High-Concentration Ozone-Water Using Freestanding Perforated Diamond Electrodes

High-concentration ozone-water can be directly produced with a zero-gap electrolytic cell containing a freestanding perforated boron-doped diamond electrode. For the sake of improving current efficiency for electrochemical ozone-water production, optimization of the electrode configuration was performed. It was proven that the number of holes, hole size, and electrode thickness affect current efficiency. In particular, increasing the number of holes per unit area was the most effective method for improving current efficiency. In regard to hole size, 1 mm diameter was more appropriate than 1.5 mm diameter. Electrode thickness affected the current efficiency, and maximum values were found to be around 0.5-0.6 mm. Based on these results, an electrode optimal for electrochemical ozone-water production was prepared and achieved a maximum current efficiency of 47% in moderate conditions thus far.

Fabrication of vertically aligned diamond whiskers from highly boron-doped diamond by oxygen plasma etching.

Conductive diamond whiskers were fabricated by maskless oxygen plasma etching on highly boron-doped diamond substrates. The effects of the etching conditions and the boron concentration in diamond on the whisker morphology and overall substrate coverage were investigated. High boron-doping levels (greater than 8.4 × 10(20) cm(-3)) are crucial for the formation of the nanosized, densely packed whiskers with diameter of ca. 20 nm, length of ca. 200 nm, and density of ca. 3.8 × 10(10) cm(-2) under optimal oxygen plasma etching conditions (10 min at a chamber pressure of 20 Pa). Confocal Raman mapping and scanning electron microscopy illustrate that the boron distribution in the diamond surface region is consistent with the distribution of whisker sites. The boron dopant atoms in the diamond appear to lead to the initial fine column formation. This simple method could provide a facile, cost-effective means for the preparation of conductive nanostructured diamond materials for electrochemical applications as well as electron emission devices.

Application of Freestanding Perforated Diamond Electrodes for Efficient Ozone-Water Production

The application of diamond electrodes is promising for electrolyzing water to produce ozone because of their superior chemical and dimensional stability, as well as their large overpotential for the oxygen evolution reaction. A freestanding conductive diamond plate was perforated to prepare a freestanding perforated diamond electrode, which was incorporated into a zero-gap electrolytic cell for direct electrochemical ozone-water production. This system has many advantages, in particular, that it exhibits the highest current efficiency (29%) reported for the electrochemical ozone-water production thus far.