In this study, corncob was explored as a low-cost and abundant precursor for the preparation of activated carbon via carbonization and the KOH activation method. The alkaline/biochar ratios varied from 3:1 to 5:1, and the activation temperatures ranged from 700 to 900 °C. The characterized results reveal that the alkaline/biochar ratios and activation temperatures had a remarkable influence on the morphology and microstructure of as-prepared activated carbon (CAC_T-R). The CAC_T-R presented a porous structure with a large number of micropores and a small number of mesopores. The reasonable distribution of micropores and mesopores endows the ideal structure for ion transfer and charge storage. The optimal sample CAC_700-4 exhibited the best capacitive performance with a specific capacitance of 260 F/g at 1 A/g. Moreover, the assembled CAC_700-4//CAC_700-4 symmetric supercapacitor showed a high energy density of 14.3 Wh/kg at a power density of 250 W/kg in 6 M KOH electrolyte. It also has a capacitance retention of 95.5% after 10,000 cycles, indicating its excellent cycle stability. These results indicate that corncob-derived activated carbon provides the possible application of biomass waste in high-performance supercapacitors.

Utilizing lignin-derived activated carbon in supercapacitors has emerged as a promising approach to alleviating environmental pollution and promoting the high-value utilization of byproducts in the papermaking industry. In this study, activated carbons (LACs) were prepared using a simple one-step KOH activation approach and by employing enzymatic hydrolysis lignin (EHL). The impact of the KOH activation parameters on the microstructure and capacitive performance of the LACs was investigated by varying the KOH/EHL ratio and activation temperature. The optimized sample LAC_800-4 showed an interconnected porous structure with a high surface area of 2285 m²/g, abundant micropores, and a small number of mesopores, which makes it a suitable electrode material for supercapacitors. The sample LAC_800-4 demonstrated a high specific capacitance of 291.3 F/g in a three-electrode system. Under a symmetrical supercapacitor electrode system, the specific capacitance of the LAC_800-4 electrode reached 186.8 F/g at 0.5 A/g. After 10,000 cycles at 20 A/g, the capacitance retention rate remained at 96.1%. The symmetrical supercapacitor also demonstrated a superior energy density of 6.5 Wh/kg. This work provides valuable insights into the transformation of low-value natural biomass derivatives into environmentally friendly, high-performing supercapacitor electrode materials.

Fast pyrolysis of microcrystalline cellulose (MC) was carried out by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The effects of temperature, time, and a catalyst on the distribution of the pyrolysis products were analyzed. The reaction temperature and time can significantly affect the types and yields of compounds produced by cellulose pyrolysis. A pyrolysis temperature of 500–600 °C and pyrolysis time of 20 s optimized the yield of volatile liquid in the pyrolysis products of cellulose. In all catalytic experiments, the relative contents of alcohols (1.97%), acids (2.32%), and esters (4.52%) were highest when K₂SO₄ was used as a catalyst. HZSM-5 promoted the production of carbohydrates (92.35%) and hydrocarbons (2.20%), while it inhibited the production of aldehydes (0.30%) and ketones (1.80%). MCM-41 had an obvious catalytic effect on cellulose, increasing the contents of aldehydes (41.58%), ketones (24.51%), phenols (1.82%), furans (8.90%), and N-compounds (12.40%) and decreasing those of carbohydrates (5.38%) and alcohols (0%).

Currently, the development of nonmetallic oxygen reduction reaction (ORR) catalysts based on heteroatomic-doped carbon materials is receiving increaseing attention in the field of fuel cells. Here, we used enzymolytic lignin (EL), melamine, and thiourea as carbon, nitrogen, and sulfur sources and NH₄Cl as an activator to prepare N- and S-codoped lignin-based polyporous carbon (ELC) by one-step pyrolysis. The prepared lignin-derived biocarbon material (ELC-1-900) possessed a high specific surface area (844 m² g⁻¹), abundant mesoporous structure, and a large pore volume (0.587 cm³ g⁻¹). The XPS results showed that ELC-1-900 was successfully doped with N and S. ELC-1-900 exhibited extremely high activity and stability in alkaline media for the ORR, with a half-wave potential (E_1/2 = 0.88 V) and starting potential (E_onset = 0.98 V) superior to those of Pt/C catalysts and most non-noble-metal catalysts reported in recent studies. In addition, ELC-1-900 showed better ORR stability and methanol tolerance in alkaline media than commercial Pt/C catalysts.

Porous carbon holds great potential for application in supercapacitors due to its rich pore structure and high specific surface area. In this research, lignin served as the starting material for the production of lignin-derived carbon materials via a carbonization-activation process. The resulting porous carbon materials underwent rigorous characterization using SEM, BET, Raman, XRD, and XPS to uncover their morphological and structural intricacies. Notably, the optimal product, achieved with a mass ratio of lignin to KOH and KCl at 1:2:0.5 and activation temperature at 700 °C, emerges as an excellent electrode material for high-performance supercapacitors. This superior carbon material boasts a remarkable specific surface area of 2730 m² g⁻¹, demonstrating an electrochemical capacitance up to 406 F/g at 1 A/g, its high performance surpasses many existing carbon materials. To further investigate the potential application of ELC in electric double-layer capacitors, the electrochemical properties of ELC in 6 M KOH, 1 M Na₂SO₄, and 1 M Et₄NBF₄/PC electrolytes were investigated, the reasons for the differences in ELC’s electrochemical performance in different electrolytes are discussed and analyzed in detail, and the advantages and disadvantages of ELC’s performance in capacitor devices of different systems are compared and analyzed. This was performed to compare the electrochemical performance of ELC and commercial YP-50F capacitor carbon in an electric double-layer capacitor, and to investigate the potential application of ELC.