One-Pot Synthesis of Sulfur and Nitrogen Co-Functionalized Graphene Material using Deep Eutectic Solvents for Supercapacitors

Thiocyanogen-modulated N, S Co-doped lignin hierarchical porous carbons for high-performance aqueous supercapacitors

Constructing heteroatom-doped porous carbons with distinct charge storage properties is significant for high-energy-density supercapacitors, yet it remains a formidable challenge. Herein, we employed a thiocyanogen-modulated alkali activation strategy to synthesize N and S co-doped lignin hierarchical porous carbon (NSLHPC). In this process, thiocyanogen serves as a surface modulation mediator to substitute oxygen with nitrogen and sulfur species, while the combination of KOH activation and MgO template generates numerous nanopores within the carbon structure. The three-dimensional interconnected nanosheet architecture facilitates rapid ion transfer and enhances accessibility to active sites. Density functional theory (DFT) calculations demonstrate that introducing N and S heteroatoms through oxygen substitution reduces the adsorption energy barrier of Zn2+. Consequently, the optimized NSLHPC exhibits a remarkable specific capacitance of 438F/g at 0.5 A/g in 6 M KOH, delivering an energy density of 10.4 Wh/kg in the symmetric supercapacitor and an impressive energy density of 104.9 Wh/kg in the zinc-ion hybrid capacitor. The NSLHPC cathode also shows an excellent lifespan with capacitance retention of 99.0 % and Columbic efficiency of 100 % over 10,000 cycles. This study presents innovative strategies for engineering high-performance porous carbon electrode materials by emphasizing pore structure modulation and N, S co-doping as crucial approaches.

Lamellar Graphene Oxide-Based Composite Membranes for Efficient Separation of Heavy Metal Ions and Desalination of Water

Sufficient efforts have been carried out to fabricate highly efficient graphene oxide (GO) lamellar membranes for heavy metal ion separation and desalination of water. However, selectivity for small ions remains a major problem. Herein, GO was modified by using onion extractive (OE) and a bioactive phenolic compound, i.e., quercetin. The as-prepared modified materials were fabricated into membranes and used for separation of heavy metal ions and water desalination. The GO/onion extract (GO/OE) composite membrane with a thickness of 350 nm shows an excellent rejection efficiency for several heavy metal ions such as Cr⁶⁺ (∼87.5%), As³⁺ (∼89.5%), Cd²⁺ (∼93.0%), and Pb²⁺ (∼99.5%) and a good water permeance of ∼460 ± 20 L m^-2 h^-1 bar^-1. In addition, a GO/quercetin (GO/Q) composite membrane is also fabricated from quercetin for comparative studies. Quercetin is an active ingredient of onion extractives (2.1% w/w). The GO/Q composite membranes show good rejection up to ∼78.0, ∼80.5, ∼88.0, and 95.2% for Cr⁶⁺, As³⁺, Cd²⁺, and Pb²⁺, respectively, with a DI water permeance of ∼150 ± 10 L m^-2 h^-1 bar^-1. Further, both membranes are used for water desalination by measuring rejection of small ions such as NaCl, Na₂SO₄, MgCl₂, and MgSO₄. The resulting membranes show >70% rejection for small ions. In addition, both membranes are used for filtration of Indus River water and the GO/Q membrane shows remarkably high separation efficiency and makes river water suitable for drinking purpose. Furthermore, the GO/QE composite membrane is highly stable up to ∼25 days under acidic, basic, and neutral environments as compared to GO/Q composite and pristine GO-based membranes.

DES mediated synthesis of sewage sludge-derived B, N-doped carbons for electrochemical applications

In order to effectively utilize organic matter in sewage sludge (SS), a new porous carbon material was successfully prepared from SS with deep eutectic solvents (DES) (boric acid and urea), in which DES was firstly used to solvent to separate organic matter, also playing the role as a B and N donor as well as acid activator to form porous B, N-carbons. As-synthesized B, N-carbon electrode materials possessed a high specific capacitance of 251.4 F/g at a current density of 1 A/g. It retained 84.28% of the capacitance at an ultrahigh current density of 5 A/g. The energy density was 9.502 Wh/Kg at a power density of 245.4 W/kg in 6 M KOH in symmetric supercapacitor.

Hierarchical Activated Carbon-MnO2 Composite for Wide Potential Window Asymmetric Supercapacitor Devices in Organic Electrolyte

The consumption of electrical energy grows alongside the development of global industry. Generating energy storage has become the primary focus of current research, examining supercapacitors with high power density. The primary raw material used in supercapacitor electrodes is activated carbon (AC). To improve the performance of activated carbon, we used manganese dioxide (MnO₂), which has a theoretical capacitance of up to 1370 Fg^-1. The composite-based activated carbon with a different mass of 0-20% MnO₂ was successfully introduced as the positive electrode. The asymmetric cell supercapacitors based on activated carbon as the anode delivered an excellent gravimetric capacitance, energy density, and power density of 84.28 Fg^-1, 14.88 Wh.kg^-1, and 96.68 W.kg^-1, respectively, at 1 M Et₄NBF₄, maintaining 88.88% after 1000 test cycles.

2D amorphous bi-metallic NiFe nitrides for a high-efficiency oxygen evolution reaction

Two-dimensional bi-metallic NiFe nitrides (2D NiFe-N) are successfully synthesized in the designed ternary deep eutectic solvents under the guidance of DFT calculations. Taking advantage of the unique properties of large-size, ultrathin amorphous 2D structure and modulable electronic structure, the NiFe_0.05-N exhibits extraordinary OER performance with relatively low overpotential of 238 mV at 10 mA cm^-2 and durable stability.

Deep Eutectic Solvents for High-Temperature Electrochemical Capacitors

This article provides an overview of a deep eutectic mixture based on the application of lithium nitrate (V) and acetamide as an electrolyte in a carbon-based electrochemical capacitor. This type of electrolyte is intended to be applied in devices designed for operation under critical conditions (e. g., extreme temperatures). In contrast to water- and common organic-based formulations, the proposed electrolyte ensures good device performance at 100 °C. To describe the chemistry of the proposed mixture, infrared and Raman spectroscopy, differential scanning calorimetry, and gas chromatography with mass spectrometry were used. Electrochemical analysis includes the verification of system ageing, self-discharge monitoring, leakage current measuring, and fundamental testing related to determining the specific capacitance or maximum voltage. Additionally, comprehensive analysis of the lithium nitrate salt and organic solvent addition to the operating system was carried out, including the replacement of lithium ions with sodium or potassium.

Eutectics: formation, properties, and applications

Various eutectic systems have been proposed and studied over the past few decades. Most of the studies have focused on three typical types of eutectics: eutectic metals, eutectic salts, and deep eutectic solvents. On the one hand, they are all eutectic systems, and their eutectic principle is the same. On the other hand, they are representative of metals, inorganic salts, and organic substances, respectively. They have applications in almost all fields related to chemistry. Their different but overlapping applications stem from their very different properties. In addition, the proposal of new eutectic systems has greatly boosted the development of cross-field research involving chemistry, materials, engineering, and energy. The goal of this review is to provide a comprehensive overview of these typical eutectics and describe task-specific strategies to address growing demands.

Biomass Related Highly Porous Metal Free Carbon for Gas Storage and Electrocatalytic Applications

In this paper we report the synthesis of a N, S co-doped metal free carbon cryogel obtained from a marine biomass derived precursor using urea as nitrogen source. Natural carrageenan intrinsically contains S and inorganic salt. The latter also serves as an activating agent during the pyrolytic step. The overall 11.6 atomic % surface heteroatom concentration comprises 5% O, 4.6% N and 1% S. The purified and annealed final carbon (CA) has a hierarchical pore structure of micro-, meso- and macropores with an apparent surface area of 1070 m²/g. No further treatment was applied. The gas adsorption potential of the samples was probed with H₂, CO₂ and CH₄, while the electrocatalytic properties were tested in an oxygen reduction reaction. The atmospheric CO₂ and CH₄ storage capacity at 0 °C in the low pressure range is very similar to that of HKUST-1, with the CO₂/CH₄ selectivity below 20 bar, even exceeding that of the MOF, indicating the potential of CA in biogas separation. The electrocatalytic behavior was assessed in an aqueous KOH medium. The observed specific gravimetric capacitance 377 F/g was exceeded only in B, N dual doped and/or graphene doped carbons from among metal free electrode materials. The CA electrode displays almost the same performance as a commercial 20 wt% Pt/C electrode. The oxygen reduction reaction (ORR) exhibits the 4-electron mechanism. The 500-cycle preliminary stability test showed only a slight increase of the surface charge.

CO2 switchable deep eutectic solvents for reversible emulsion phase separation

CO₂ switchable imidazole-based deep eutectic solvents (DESs) were formed and used for reversible phase separation of emulsions generated between DESs and oil.

Micropores within N,S co-doped mesoporous 3D graphene-aerogel enhance the supercapacitive performance

Micropores within N,S co-doped mesoporous 3D graphene-aerogel enhances supercapacitive performance.

Novel approach towards the synthesis of highly efficient flame retardant electrode and oil/organic solvent absorber

We have developed a facile one pot process to synthesize an ultra-light functionalized spongy graphene (FSG). This is the first approach to use carbon based flame retardant spongy material as an electrode to build completely flame retardant supercapacitor (FRS) also as an oil/organic solvent absorber. The fully FRS concept has created by the compilation of as-prepared FSG with flame retardant separator and electrolyte. As-prepared FSG contained high amount of phosphorus and nitrogen functional groups, which makes it potent flame retardant electrochemical material, to use it as an efficient FR electrode. Flame test of FSG revealed that it doesn't catch fire for ∼1500 s. Also, FSG was able to sustain flame retardancy at a temperature as high as 1500 °C for continuous exposure of ∼300 s. FSG used as an electrode for symmetric capacitor possessing maximum specific capacitance of 494.3 F g^-1 at a current density 1 A g^-1. Corresponding high energy density and power density values are 55.6 Wh kg^-1 and 1799 W kg^-1. It shows cycling stability of 86.1% after 5000 cycles at current density of 10 A g^-1. The electrochemical property of FSG was also confirmed using three electrode system. Flame retardant FSG material was also used for the absorption and recovery of oil and organic solvents. FSG has high oil and organic solvent sorption capacity in the range of 40-70 g/g, also can be reused for minimum 10 cycles. Such approach has great significance for multifunctional graphene based nanocomposites will open the new window for large-scale applications.