Table 2.
Electrodes prepared from hydrothermally treated biopolymers and raw biomass.
| Electrode Material |
Synthesis Method | Electrolyte | Stability | Microporosity (%) | BET Area (m2/g) | Cap (F/g) 1 |
|---|---|---|---|---|---|---|
| Biopolymers | ||||||
| AC from chitosan [192] | HTC (250 °C, 4 h), KHCO3 activ. ** (750 °C) | 1 M H2SO4 | 75% at 10 A/g | 36% | 2124 | 265/326 * |
| AC from cellulose and thiourea [189] | HTC (240 °C, 1 h) and KOH (3:1) activ. at 800 °C | 6 M KOH | Stable after 20,000 cycles | Mainly microporous | 952 | 224/236 * |
| Cellulose/AC/GO hydrogel [188] | Straw heating (500 °C) and KOH (3:1) activ. at 700 °C. HTC (180 °C, 1 h) of a cellulose, AC and GO mixture. | Lignin hydrogel |
88% after 10,000 cycles | Hierarchical structure (micro, meso and macro) | 762 | 208/565 * |
| Cellulose-based AC. [132] | HTC (250 °C cell; 230 °C starch, 2 h) and KOH (4:1) activ. at 700 °C | 1 M TEABF4/AN | 65% at 20 A/g. | 87% | 2457 | 170 |
| AC from starch. [132] | 65% at 20 A/g. | 87% | 2273 | 161 | ||
| Lignin derived AC [193] | HTC (220 °C, 14 h) in H2SO4 (aq.), KOH (1:1) activ. at 800 °C | 6 M KOH | 98% after 5000 cycles | 76% | 1337 | 110/255 * |
| Raw biomass | ||||||
| Wood sawdust derived AC. [194] | HTC (120 °C, 2 h) in KOH (aq.) and carbonization at 800 °C | 6 M KOH | 99% after 5000 cycles. | 74%. | 1185 | 244/302 * |
| AC from coconut shells. [134] | HTC (200 °C, 20 min) in H2O2 aq., HTC (275 °C, 12 h) in ZnCl2 aq. and CO2 activ. (800 °C) | 0.5 M H2SO4 | 88% after 2000 cycles. | Mesoporous structure | 2440 | 207 |
| AC from wood sawdust. [132] | HTC (250 °C, 2 h) and KOH (4:1) activ. at 800 °C | 1 M TEABF4/AN | 75% at 20 A/g. | 89% | 2967 | 197 |
| Enteromorpha Prolifera-based AC. [195] |
HTC (180 °C, 24 h), heating at 450 °C, KOH (2:1) activ. at 700 °C | 6 M KOH | 90% after 10,000 cycles. | 88% | 1528 | 192 |
| AC from Spirulina platensis and glucose. [133] | HTC (180 °C, 24 h) and KOH (2:1) activ. at 700 °C | 6 M LiCl | 98% after 10,000 cycles. | 93% | 2130 | 177 |
| Jatropha derived AC. [196] | HTC (190 °C, 2 h) and KOH (1:1) activ. at 800 °C | 1 M KOH | 19% Increase after 5000 cycles. | Large micro and macropores. | 747 | 175 |
| AC from hemp fibers. [131] | HTC (180 °C, 24 h) in H2SO4 (aq.), KOH (1:1) activ. at 750 °C | BMPY TFSI | 90% at 100 A/g | 47% | 2287 | 160 |
| AC from corn straws. [136] | HTC (220 °C, 12 h) and KOH (1:1) activ. at 800 °C | 6 M KOH | 83% after 2000 cycles. | Mainly microporous. | 1229 | 66/271 * |
1 Specific capacitance measured at 1 A/g (unless specified otherwise) on a two-electrode system. * Values in a 3-electrode setup. ** Activ. = Activation.