Preparation of Carbon Powder from HPC Derived from Sub-Bituminous Coal (SB-HPC) And Discussion of Its Properties as An EDLC Electrode Material
Okuma S, Moriyasu Y, Inoue T, Shishido T, Hamaguchi M and Toyoda M
Published on: 2024-03-06
Abstract
Carbon precursor powders were prepared by the precipitation method using HPC derived from subbituminous coal as a raw material, carbonized at different temperatures, and the carbonization temperature dependence of the surface properties and EDLC properties of the obtained carbon powders was investigated. The specific surface area obtained carbon material increased with increasing carbonization temperature, reaching a maximum of 1268 m2 g-1 at a carbonization temperature of 1200oC without activation. Its micropores (Dave.) formed in the obtained carbon powder was 0.67 to 0.71 nm, suggesting that it has ultra-micropores, which are extremely fine among the micropores. On the other hand, at the carbonization temperature of 1300 oC, Dave increased to 0.78 nm and the specific surface area decreased. It was inferred that this was due to the expansion of the pore diameter due to the connection of micropores. Carbon powders treated at different carbonization temperatures were applied as electrode materials in a water-based EDLC with 40% H2SO4 as the electrolyte. At a current density of 50 mA g-1, the capacities per weight were 284 F g-1, 265 F g-1, 281 F g-1, 254 F g-1 and 212 F g-1 at carbonization temperatures from 900 to 1300 oC. A comparison of the oxidation/reduction peak areas obtained by CV measurement showed that the oxidation/reduction peak areas obtained by CV measurement showed the maximum at a carbonization temperature of 900oC, suggesting that the surface oxygen-containing functional groups. We investigated the pore characteristics and EDLC characteristics as the effect of CO2 activation on carbon powder derived from SB-HPC. Micropores were formed in the SB-HPC-derived carbon powder after activation, and the specific surface area increased to 1675 m2 g-1 after 3.0 h of activation. When the activated carbon powder was applied to the EDLC electrode material, an increase in the capacitance per unit weight was observed as the specific surface area increased. However, since the capacitance per volume decreased, it was inferred that the unactivated carbon powder on SB-HPC, which showed excellent capacitance per weight and per volume, is suitable for the EDLC electrode material.