Optimization of K₂CO₃ green activation of lignite for high-performance porous carbon and its application in supercapacitors

The pathway to sustainable development and carbon neutrality is contingent upon the development of high-performance porous carbon electrode materials sourced from biomass and industrial waste. The present research introduces an innovative approach for the fabrication of porous carbon, harnessing the collaborative impact of various materials to transform biomass in the form of corncobs and industrial byproduct fly ash into tiered porous carbon characterized by a high specific surface area and excellent functionality, via a simple hydrothermal activation method. This material is particularly well-suited for applications in supercapacitors, lithium-ion batteries, and other energy storage systems. The porous carbon material fabricated from these two waste streams boasts a wealth of pores and an exceptional specific surface area (1,768 m2 g-1), which in turn confers superior electrochemical performance. The material achieves a remarkable specific capacitance of up to 240 F g-1 (at 1 A g-1), and demonstrates remarkable properties for lithium storage. Lithium-ion batteries constructed with this material feature an extensive potential range, with an initial specific capacity of 160 mAh g-1 at 0.1 A g-1, and a near-perfect coulomb efficiency of approximately 100%. This research uncovers a novel paradigm for the preparation of high-performance porous carbon electrode materials through a low-carbon and environmentally conscious approach. It not only advances the pursuit of carbon neutrality and the realization of carbon peak objectives but also underscores the potential of valorizing biomass and industrial byproducts in the context of cutting-edge energy storage technologies.

One-step converting biowaste wolfberry fruits into hierarchical porous carbon and its application for high-performance supercapacitors

Fabrication of flexible hierarchical porous nitrogen-doped carbon nanofiber films for application in binder-free supercapacitors

Carbon materials with porous structures with their unique surface area and charge transport properties have been attracting significant attention as electrode materials in renewable energy storage devices. The rapid agglomeration of layered materials during electrochemical processes reduces their shelf life and specific capacitance, which can be prevented by the introduction of suitable pores between the layers. In this study, resorcinol-based porous resin carbon was facilely prepared via a simple carbonization of the potassium salts of resorcinol-potassium resin. The morphology, structure and surface properties of the carbon materials were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption and energy dispersive spectroscopy (EDS). It is proposed that the fast nucleophilic addition between the phenols and formaldehyde produces nano-sized gel particles, followed by carbonization into carbon particles, finally packing to the mesopores. Due to the synergistic effects of the tailored porosity and O-doping, the prepared carbon materials show a high specific capacitance (198 F g−1 for RC700), good capacitance retention (96.5% for RC700) at 2 A g−1 in 6 M KOH and the specific area of RC700 is 540 m2 g−1.

The development of high-performance biomass-derived porous graphitic carbon materials is in high demand for applications in supercapacitors. Herein, a novel N, S self-codoped porous graphitic carbon is synthesized by one-step carbonization of lotus leaves together with urea and ferric chloride. Due to the combination of urea as a nitrogen doping agent and ferric chloride as both activating agent and graphitization catalyst, the obtained lotus leaf–derived porous graphitic carbon material possesses a high specific surface area of 975.7 m2 g−1, appropriate pore structure with interconnected macropores, suitable graphitization level, and high N, S contents. The resultant porous graphitic carbon electrode shows a high specific capacitance of 385.0 F g−1 at 0.5 A g−1 (based on a three-electrode system in 6 M KOH electrolyte), and good rate capability (140.0 F g−1 at 100 A g−1). Furthermore, the assembled carbon-based symmetric supercapacitor delivers a high energy density of 29.5 Wh kg−1 at a power density of 545.6 W kg−1 and excellent long-term cycling stability (95.3% of the initial capacitance after 20,000 cycles at 5 A g−1). This work provides a general method to synthesize porous graphitic carbon from biomass for electrochemical energy storage and conversion.

High surface area and large pore volume carbon materials having hierarchical nanoporous structure are required in high performance supercapacitors. Such nanoporous carbon materials can be fabricated from organic precursors with high carbon content, such as synthetic biomass or agricultural wastes containing cellulose, hemicellulose, and lignin. Using recently developed unique concept of materials nanoarchitectonics, high performance porous carbons with controllable surface area, pore size distribution, and hierarchy in nanoporous structure can be fabricated. In this review, we will overview the recent trends and advancements on the synthetic methods for the production of hierarchical porous carbons with one- to three-dimensional network structure with superior performance in supercapacitors applications. We highlight the promising scope of accessing nanoporous graphitic carbon materials from: (i) direct conversion of single crystalline self-assembled fullerene nanomaterials and metal organic frameworks, (ii) hard- and soft-templating routes, and (iii) the direct carbonization and/or activation of biomass or agricultural wastes as non-templating routes. We discuss the appealing points of the different synthetic carbon sources and natural precursor raw−materials derived nanoporous carbon materials in supercapacitors applications.

Supercapacitors are high-power energy storage devices due to their charge storage capability and long cyclic stability. These devices rely on highly porous materials for electrodes providing a substantial surface area per mass, such as highly porous carbon. Developing high-performance porous carbon from biomass wastes such as waste-activated sludge and spent coffee is a sustainable way to reduce adverse environmental effects, contributing toward a carbon circular economy. In this study, hierarchically porous carbon with a high surface area of 1198 ± 60 m2 g-1 was synthesized through a green route. Sodium acetate was utilized as an environmentally friendly electrolyte. The long-term stability test at a high current density was conducted, providing valuable insights into the viability of sodium acetate as a robust electrolyte in supercapacitor application. The supercapacitor demonstrated an excellent cycle stability of 98.4% after 20,000 cycles at a current density of 10 A g-1 in sodium acetate. Further assessment revealed dominant fast surface kinetics. Moreover, a maximum energy density of 15.9 Wh kg-1 at 0.2 A g-1 was achieved. By utilizing highly porous carbon in conjunction with a water-based binder, a substantial improvement of 76% in capacity with respect to a nonaqueous-based binder was demonstrated.

From barley straw biomass to N/S co-doped as electrode material for high-performance supercapacitor applications

The development of low-cost, high-purity and high-performance porous carbon is of great significance for promoting the commercial application of supercapacitors. In this paper, porous carbon spheres (PCSs) with excellent electrochemical performance were obtained by carbonization and activation of starch gel spheres as precursor which is prepared by microemulsion process. The obtained PCSs exhibit both microporous and mesoporous structure, showing a large specific surface area of 1117.0 m2 g[Formula: see text] and exhibiting a high specific capacitance of 221.3 F g[Formula: see text]at a current density of 0.5 A g[Formula: see text] in aqueous electrolyte (and still displays capacity of 146.0 F g[Formula: see text] in ion liquid electrolyte). The PCSs//PCSs symmetric supercapacitor (SSC) based on aqueous electrolyte exhibits an energy density of 10.9 Wh kg[Formula: see text] at a power density of 300.0 W kg[Formula: see text], whereas that based on ion liquid electrolyte achieves a high energy density of 29.0 Wh kg[Formula: see text] at 650.0 W kg[Formula: see text]. The study provides a new idea to develop low-cost, high-purity and high-performance porous carbon materials for supercapacitors.

Supercapacitors have rapidly evolved into one of the important components in energy storage technology with the capability of storing and discharging energy very quickly and effectively. The fabrication of a high-performance supercapacitor carbon electrode via a large-scale printing process can accelerate its commercialization. Herein, a high-performance supercapacitor carbon electrode is processed via a micro-gravure roll-to-roll (R2R) printing technique, and the properties are optimized through web tension, printing speed and morphology control. The supercapacitor with carbon electrodes fabricated by R2R micro-gravure printing shows a capacitance of 151.15 F g−1 and equivalent series resistance (ESR) of 0.37 Ω, which are comparable to the carbon electrodes fabricated via conventional coating. Furthermore, the electrodes show highly promising performance in the application of solid-state supercapacitors, and the light-emitting diode working for nearly 30 s. The research demonstrates that the low-cost, large-scale R2R micro-gravure printing process can be used to produce high-quality electrodes for the supercapacitor, which will accelerate the development of a fully R2R micro-gravure printed supercapacitor and its commercialization.

One-pot synthesis of potassium benzoate-derived porous carbon for CO2 capture and supercapacitor application

This paper shows a new classification of preparing biomass-based porous carbon materials. The design of high-performance biomass-based porous carbon materials and their recent progress in the field of supercapacitors are reviewed.

MnO2-introduced-tunnels strategy for the preparation of nanotunnel inserted hierarchical-porous carbon as electrode material for high-performance supercapacitors

Utilization of cigarette butt waste as functional carbon precursor for supercapacitors and adsorbents

Utilization of high‑sulfur-containing petroleum coke for making sulfur-doped porous carbon composite material and its application in supercapacitors