Facile synthesis of N/B co-doped hierarchically porous carbon materials based on threonine protic ionic liquids for supercapacitor

Constructing the Interconnected and Hierarchical Nanoarchitectonics in Coal-Derived Carbon for High-Performance Supercapacitor

Because of the deep and zigzag microporous structure, porous carbon materials exhibit inferior capacitive performance and sluggish electrochemical kinetics for supercapacitor electrode materials. Herein, a single-step carbonation and activation approach was utilized to synthesize coal-based porous carbon with an adjustable pore structure, using CaO as a hard template, KOH as an activator, and oxidized coal as precursors to carbon. The obtained sample possesses an interconnected and hierarchical porous structure, higher SSA (1060 m2 g-1), suitable mesopore volume (0.25 cm3 g-1), and abundant surface heteroatomic functional groups. Consequently, the synthesized carbon exhibits an exceptionally high specific capacitance of 323 F g-1 at 1 A g-1, along with 80.3% capacitance retention at 50 A g-1. The assembled two-electrode configuration demonstrates a remarkable capacitance retention of up to 95% and achieves Coulombic efficiency of nearly 100% with 10,000 cycles in a 6 M KOH electrolyte. Furthermore, the Zn-ion hybrid capacitor also exhibits a specific capacity of up to 139.1 mA h g-1 under conditions of 0.2 A g-1. This work offers a simple method in preparation of coal-based porous carbon with controllable pore structure.

Fabrication of N-Doped Porous Carbon with Micro/Mesoporous Structure from Furfural Residue for Supercapacitors

N-doping is a very useful method to improve the electrochemical performance of porous carbon (PC) materials. In this study, the potential of furfural residue (FR), a solid waste in furfural production, as a precursor to producing PC materials for supercapacitors was highlighted. To obtain an N-doped PC with a high specific surface area (SSA) and hierarchical porous structure, the urea-KOH synergistic activation method was proposed. The obtained FRPCK-Urea showed a high SSA of 1850 m2 g-1, large pore volume of 0.9973 cm3 g-1, and interconnected micro/mesoporous structure. Besides, urea can also serve as a nitrogen source, resulting in a high N content of 5.31% in FRPCK-Urea. These properties endow FRPCK-Urea with an excellent capacitance of 222.7 F g-1 at 0.5 A g-1 in 6 mol L-1 KOH aqueous electrolyte in a three-electrode system. The prepared FRPCK-Urea possessed a well capacitance retention at current densities from 0.5 to 20 A g-1 (81.90%) and cycle durability (96.43% after 5000 cycles), leading to FRPCK-Urea to be a potential electrode material for supercapacitors. Therefore, this work develops an effective way for the high-valued utilization of FR.

Versatile Synthesis of Carbon Materials using Protic Ionic Liquids and Salts as Precursors

Carbon materials (CMs) hold immense potential for applications across a wide range of fields. However, current precursors often confront limitations such as low heteroatom content, poor solubility, or complicated preparation and post-treatment procedures. Our research has unveiled that protic ionic liquids and salts (PILs/PSs), generated from the neutralization of organic bases with protonic acids, can function as economical and versatile small-molecule carbon precursors. The resultant CMs display attractive features, including elevated carbon yield, heightened nitrogen content, improved graphitic structure, robust thermal stability against oxidation, and superior conductivity, even surpassing that of graphite. These properties can be elaborate modulated by varying the molecular structure of PILs/PSs. In this Personal Account, we summarize recent developments in PILs/PSs-derived CMs, with a particular focus on the correlations between precursor structure and the physicochemical properties of CMs. We aim to impart insights into the foreseeable controlled synthesis of advanced CMs.

Highly active N, S Co-Doped Ultramicroporous Carbon for High-Performance Supercapacitor Electrodes

N, S-doped ultramicroporous carbons (NSUC-x) with a high nitrogen/sulfur content and a narrow pore-size distribution of around 0.55 nm were firstly prepared using L-cysteine as a nitrogen and sulfur source. The phase, graphitization degree, morphology, specific surface area, pore structure and surface condition of NSUC-x are investigated to analyze the key role in electrochemical performance. Such an ultramicroporous structure and N, S doping not merely provide a high-specific surface area and a suitable pore size, but also induce a good wettability for the fast transport and adsorption of electrolyte ions. Due to the above strategies, the typical NSUC-0.4 exhibits a high gravimetric capacitance of 339 F g⁻¹ at 0.5 A g⁻¹ as well as a capacity retention of 91.6% after 10,000 cycles in a three-electrode system using a 6 M KOH electrolyte. More attractively, a NSUC-0.4-assembled symmetrical supercapacitor delivers an energy output of 7.4 Wh kg⁻¹ at 100 W kg⁻¹ in 6 M KOH as well as a capacity retention of 92.4% after 10,000 cycles, indicating its practical application prospect. Our findings open up new prospects for the design and electrochemical application of N, S-doped ultramicroporous carbons.

A Chlorine-Based Redox Electrochemical Capacitor

Electrochemical capacitors are under the spotlight due to their high power density, but they have a low energy density. Redox electrolytes have emerged as a promising approach to design high-energy electrochemical energy storage devices. Herein, a chlorine-based redox electrochemical capacitor is reported in an ionic liquid electrolyte. The commercial activated carbon is employed as the working electrode to render the reversible redox of chloride ions in an ionic liquid, by the restriction of micropores on neutral chlorine. The carbon material can simultaneously provide electrical double-layer capacitance. The effective integration of a chlorine redox reaction and electrical double layer allows for high-energy electrochemical capacitors. By this means, a rechargeable chlorine-based redox electrochemical capacitor with reversible capacity and good rate capability and cycling stability is obtained. This work offers a solution for a new type of high-energy electrochemical capacitors.