(Invited) Preparation of Boron-Doped Nanodiamond and Its Application to Aqueous Electrochemical Capacitors
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2024-11-22 |
| Journal | ECS Meeting Abstracts |
| Authors | Takeshi Kondo |
Abstract
Section titled āAbstractāBoron-doped diamond (BDD) is known to be a functional electrode material that can be used in various electrochemical applications such as sensitive electroanalysis and efficient electrolysis, based on the unique electrochemical properties including wide potential window and low background current, as well as extreme physical/chemical stabilities. Usually, BDD electrodes are prepared by deposition of a polycrystalline BDD thin film on a conductive substrate. In this form, the specific surface area is too small to be used as an electrochemical capacitor. Thus, we have developed boron-doped nanodiamond (BDND) powder as a conductive diamond powder with a large specific surface area. BDND exhibits wider potential window in aqueous electrolytes than activated carbon (AC). Therefore, the BDND is expected to be used for an electrode material of aqueous EDLC with a large cell voltage. Nanodiamond powder (primary particle size: 4 nm) was used as a substrate material for BDND. BDD was deposited on the agglomerate of dry nanodiamond powder via microwave plasma-assisted chemical vapor deposition (CVD). The as-deposited BDND was then treated by air oxidation at 425 Ā°C to minimize sp 2 carbon components to obtain BDND. Test electrode was prepared by casting an ink containing BDND on a glassy carbon disk electrode as a current collector. For an EDLC pouch cell, BDND paste containing PVDF binder was applied on the both sides of a titanium sheet current collector to form an electrode. Two electrodes with a separator in between was put in a plastic bag and aqueous electrolyte was poured in the bag to form a pouch cell. The BDND was found to show a relatively large specific surface area of 650 m 2 g ā1 and good conductivity of ~1 S cm ā1 . CV in 1 M H 2 SO 4 at the BDND test electrode in a three-electrode configuration showed a wide potential window of 3 V, which was significantly wider than that of an AC test electrode (1.5 V). In a symmetric two-electrode system, cell voltage of a CV in 1 M H 2 SO 4 was found to be larger at the BDND electrode (1.8 V) than at the AC electrode (0.8 V). Therefore, wide potential window of the BDND was confirmed to be useful for creation of an aqueous EDLC with a large cell voltage. In addition, the use of saturated NaClO 4 as an electrolyte was shown to be effective for an extremely large cell voltage of 2.8 V, which can further enlarge the energy and power densities of an aqueous EDLC. CV of BDND/saturated NaClO 4 system exhibited a high energy density of 20 Wh kg ā1 and a high power density of 10 4 W kg ā1 . Similar charge-discharge properties were also shown at EDLC pouch cells with BDND/concentrated NaClO 4 system.