Boron-Doped Diamond Powders for Aqueous Supercapacitors with High Energy and High Power Density

Abstract

The electrochemical properties of boron-doped diamond powder (BDDP) were investigated as a step toward its application to aqueous electric double-layer capacitors (EDLCs). Conductive BDDPs (particle size: 150, 350, and 3500 nm) were prepared by depositing a BDD layer on the surface of a diamond powder (DP) core with various particle sizes (100, 300, and 2600 nm) via microwave plasma-assisted chemical vapor deposition. The 150-nm-sized BDDP (BDDP-150) had a relatively large Brunauer–Emmett–Teller (BET) specific surface area (106 m2/g). Cyclic voltammetry of the BDDP electrodes in 1.0 M H2SO4 with a symmetric two-electrode system showed an operating voltage of 1.5 V, which is much larger than that of an activated carbon (AC) electrode (0.8 V). In addition, compared to the AC electrode, the BDDP electrodes showed lower capacitance-decrease ratios at fast scan rates. Hence, BDDP-150 had greater energy and power densities than the AC electrode under high rate conditions in the aqueous electrolyte. As the BDDP electrode had a larger bulk density than the AC electrode, aqueous EDLC using BDDP can be expected to be used as a space-saving electric energy storage system suitable for high-speed charging and discharging.