Synthesis of S-doped mesoporous carbon fibres with ultrahigh S concentration and their application as high performance electrodes in supercapacitors

Converting New Zealand Slash into S-Doped Electrode Materials for High-Performance Supercapacitors

Slash is a waste product generated from commercial forestry operations. In 2022, flooding slash caused devastating damage when Cyclone Gabrielle directly impacted the Hawke's Bay region of New Zealand. This study addresses the dual challenges of waste management and sustainable materials development by converting forestry slash into high-performance carbon electrodes through an innovative in situ sulfur doping process. Building upon prior research involving waste-derived materials, this study develops a hydrothermal sulfurization technique that transforms New Zealand slash into sulfur-doped, highly graphitized carbon materials with excellent energy storage properties. The hydrothermally sulfurized slash-derived electrode material (C-HS-New Zealand Slash (NZS)) exhibits a high specific capacitance of 148 F g- 1 at a current density of 0.5 A g- 1. A supercapacitor device assembles with the C-HS-NZS electrode achieves a capacitance of 440 F g- 1 at the same current density. The energy density reaches 15.3 Wh kg- 1 at a power density of 250 W kg- 1. Furthermore, the C-HS-NZS-based device delivers a maximum capacitance of 384 F g- 1 and retains 360 F g- 1 after 10,000 cycles, demonstrating excellent capacity retention and long-term electrochemical stability.

Nitrogen-doped carbons derived from cotton pulp for improved supercapacitors

Supercapacitors have a rapid charge/discharge rate, long lifespan, high stability, and relatively acceptable cost, showing great potential in energy storage and conversion applications. However, the current cost-effective carbon-based electrodes have limited application owing to their low specific capacitance and unsatisfactory stability. In this regard, we herein prepare nitrogen-doped carbons by carbonizing a mixture of cotton pulp (CCP) and melamine to improve the specific capacitance by integrating pore (mesopore) and surface (oxygen-containing groups) modification with defect engineering via the carbonization process. Furthermore, the structural and morphological features of the resultant nitrogen-doped carbons are confirmed by various characterization techniques. Excitingly, the specific capacitance for nitrogen-doped CCP (CCPN1) with a 1 : 1 weight ratio of CCP and melamine is 642 F g^-1 at a current density of 0.5 A g^-1 in a three-electrode system, surpassing that of the reported carbon analogues and most metal-based materials to date. The stability test suggests that the specific capacitance of CCPN1 is maintained over 150 F g^-1 at a current density of 2 A g^-1 even over 5000 cycles. Therefore, the reported nitrogen-doped carbons from cotton pulp exhibit improved specific capacitance and stability, providing a new cost-effective carbon-based material for application in the energy storage field.

Preparation of Sulfur-doped Carbon for Supercapacitor Applications: A Review

Electrochemical capacitors, also known as supercapacitors (SCs), have lately played an important role in energy storage and conversion systems due to their specific characteristics such as high strength, durability, and environmental friendliness. A wide range of materials is used as electrodes for SC applications because the electrochemical efficiency is primarily determined by the electrode materials used. Carbonaceous materials with unique surface, chemical, electrochemical, and electronic characteristics have become attractive for energy storage research, but they cannot meet the rising need for high specific energy and specific power. Besides, heteroatom-doped carbon materials have shown pseudocapacitance characteristics and improved specific energy, specific power, and conductivity. This makes them more adaptable in SC application. Among different heteroatom doping of carbon, S-doped carbon has gained considerable attention in SC applications due to its unpaired electrons and easily polarizable nature. S-doped carbon materials-based SCs have demonstrated enhanced surface wettability, improved conductivity, and induced pseudocapacitance effect, thereby delivering improved specific energy and specific power. Many reports on S-doped carbon for SC applications have been published, but there is no specific Review on the preparation of S-doped carbon for SC applications. This Review focuses on recent developments in the field of SC electrodes made from S-doped carbon materials. Herein, the preparation methods and applications of S-doped carbon for SCs were summarized following a brief discussion of different electrochemical characterization techniques of SCs. Finally, the challenges of S-doped carbon materials and their potential prospects were discussed to give crucial insights into the favorable factors for future innovations of SC electrodes. This Review aims to provide insight for further research on the preparation of S-doped carbon for electrochemical energy storage applications.

Waste tire heat treatment to prepare sulfur self-doped char via pyrolysis and K2FeO4-assisted activation methods

Waste tire was heat-treated to prepare sulfur self-doped chars via pyrolysis and activation processes. Pyrolytic waste tire chars were activated at different temperatures (600 °C, 800 °C, 1000 °C, and 1200 °C) with K₂FeO₄ additive ratios (mass ratio of K₂FeO₄ to char) being 0.5, 1, 2, and 3, respectively. The effective activation occurred over 600 °C with K₂FeO₄ additive ratios over 0.5. The strongest activation occurred at 1000 °C with K₂FeO₄ additive ratio of 3, and the specific capacitance increased to 129.5 F/g at 1 A/g, which was six times higher than that without K₂FeO₄. The activation mechanism revealed that higher K₂FeO₄ additive ratio promoted the transformation of large aromatic ring systems (≥6 rings) to small ones and smaller pores formation. When K₂FeO₄ additive ratio was less than 2, high ratio not only promoted alkyl-aryl C-C bonds formation, but also inhibited sulfur enrichment with S 2p_3/2 (sulphide bridge) converting to S 2p_5/2 (sulphone bridge). But when the ratio was further increased, slight decomposition of alkyl-aryl C-C bonds with the promoted conversion of S 2p_5/2 to S 2p_3/2 was witnessed. Furthermore, higher activation temperature promoted the conversion of aromatic ring systems and alkyl-aryl C-C bonds to form ordered graphitic structures. S 2p_3/2 was enriched before 800 °C, but both S 2p_3/2 and S 2p_5/2 were released at higher temperature. Formation of smaller pores was promoted before 1000 °C, but the char structure was then destroyed to form larger pores when temperature was further increased.

Sulfur self-doped char with high specific capacitance derived from waste tire: Effects of pyrolysis temperature

Preparation of sulfur self-doped char derived from waste tire (WT) was realized via two successively processes of pyrolysis and activation treatment. WT was firstly pyrolyzed at 400 °C, 600 °C, 800 °C, and 1000 °C to collect waste tire chars (WTCs) and they were subsequently activated at 800 °C with potassium ferrate (K₂FeO₄). The specific capacitance of activated waste tire chars at different pyrolysis temperatures (AWTCs-x-800) decreased from 92.60 F/g to 54.05 F/g at 1 A/g with pyrolysis temperature rising from 400 °C to 1000 °C. As for AWTCs-x-800, higher pyrolysis temperature promoted pore-forming process before 800 °C, and higher pyrolysis temperature enlarged pores after 800 °C. Increase of pyrolysis temperature promoted decomposition of alkyl-aryl CC bonds, transformation of relative small to large aromatic ring system, ordered arrangement of carbon atoms. Besides, it was found that sulfur doping content dominated in specific capacitance performance before 800 °C while surface area dominated after 800 °C. The large surface area and high S 2p_3/2 (-C-S-C-, sulphide bridge) content were beneficial for the larger specific capacitance while more S 2p_5/2 (-C-SOx-C- (x = 2-4, sulphone bridge) had the negative effect. Pyrolysis mainly affected sulfur doping properties, lower pyrolysis temperature promoted sulfur enrichment and S 2p_3/2 generation. Activation promoted surface area improvement and sulfur conversion, higher pyrolysis temperature promoted surface area improvement and sulfur release before 800 °C while the promotion effects weakened after 800 °C, and sulfur transformation of S 2p_3/2 converting to S 2p_5/2 strengthened at higher pyrolysis temperature.

High-Performance Na-Ion Storage of S-Doped Porous Carbon Derived from Conjugated Microporous Polymers

Na-ion batteries (NIBs) have attracted considerable attention in recent years owing to the high abundance and low cost of Na. It is well known that S doping can improve the electrochemical performance of carbon materials for NIBs. However, the current methods for S doping in carbons normally involve toxic precursors or rigorous conditions. In this work, we report a creative and facile strategy for preparing S-doped porous carbons (SCs) via the pyrolysis of conjugated microporous polymers (CMPs). Briefly, thiophene-based CMPs served as the precursors and doping sources simultaneously. Simple direct carbonization of CMPs produced S-doped carbon materials with highly porous structures. When used as an anode for NIBs, the SCs exhibited a high reversible capacity of 440 mAh g^-1 at 50 mA g^-1 after 100 cycles, superior rate capability, and excellent cycling stability (297 mAh g^-1 after 1000 cycles at 500 mA g^-1), outperforming most S-doped carbon materials reported thus far. The excellent performance of the SCs is attributed to the expanded lattice distance after S doping. Furthermore, we employed ex situ X-ray photoelectron spectroscopy to investigate the electrochemical reaction mechanism of the SCs during sodiation-desodiation, which can highlight the role of doped S for Na-ion storage.

Voltammetric Biosensor Based on Nitrogen-doped Ordered Mesoporous Carbon for Detection of Organophosphorus Pesticides in Vegetables

Background:

Pesticides residues in agricultural products have posed a serious threat to food safety and human health, so it is necessary to develop a rapid and accurate method to detect pesticide in the environment. N-OMC with excellent electroconductivity, high biocompatibility and the functional amino group that can be covalently attached to the enzyme can be applied to construct a sensitive and stable acetylcholinesterase biosensor for rapid and accurate detection of organophosphorus pesticides with the help of L-cysteine self-assembled monolayer and AuNPs.

Methods:

Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption measurements are used to characterize materials. Electrochemical impedance spectroscopy and cyclic voltammetry are used to study the surface features of modified electrodes. Differential pulse voltammetric is used to measure the peak current of modified electrodes. GC-MS is applied to verify the reliability of the prepared biosensor for organophosphorus pesticides detection.

Results:

N-OMC was synthesized and applied to constructed stable and sensitive acetylcholinesterase biosensors. The combination of N-OMC, L-cysteine self-assembled monolayer and AuNPs to modify the electrode surface has greatly improved the conductivity of biosensor and provided a stable platform for acetylcholinesterase immobilization. The linear detection range of paraoxon was from 3 to 24 nM with a lower detection limit of 0.02 nM.

Conclusion:

The biosensor exhibited satisfactory reproducibility, repeatability and stability, and was successfully employed to determine the paraoxon in vegetables as well as tap water samples, providing a promising tool for rapid and sensitive detection of organophosphorus pesticides in agricultural products.

Excellent Compatibility of the Gravimetric and Areal Capacitances of an Electric-Double-Layer Capacitor Configured with S-Doped Activated Carbon

Coffee grounds were converted into S-doped activated carbon (SAC) in the presence of an active agent and S dopant through a one-step synthesis approach. Carbonization, activation, and S doping was achieved through this one-step methodology. The SAC was used as an electrode material for the preparation of a symmetric electrical-double-layer capacitor (EDLC), and the influence of the loading mass of the active materials on the capacitive behaviors was investigated. The assembled SAC-based symmetric EDLC not only yielded a high capacitance but it also afforded a satisfactory capacitance retention. The symmetric EDLC constructed with loading mass SAC of 7.5 mg cm^-2 was capable of delivering a maximum gravimetric and areal capacitance of 200 F g^-1 and 1.5 F cm^-2 , respectively. The compatibility of the gravimetric and areal capacitances of SAC was mainly attributed to the high abundance of interconnected pore channels, which were beneficial for the increased contact area between electrode and electrolyte ions, fast charge transfer, and fast diffusion of the electrolyte ions. In addition to the well-developed porous networks, the introduction of S into the carbon frameworks significantly enhanced the electrical conductivity, storage capacity, and rate capability. The developed one-step synthesis provides a facile and effective route for obtaining high-performance capacitive electrode materials and realizing high value-added utilization of biomass.

Sulfur-doped mesoporous carbon via thermal reduction of CS2 by Mg for high-performance supercapacitor electrodes and Li-ion battery anodes

This paper demonstrates a facile method based on vapor-solid reaction between magnesium powder and carbon disulfide vapor to produce S-doped porous carbon. The property of the as-prepared carbon is tunable by varying the synthesis temperature. The sample synthesized at 600 °C shows the highest specific surface area, suitable for supercapacitor electrodes. A high specific capacitance of 283 F g-1 in H2SO4 aqueous electrolyte is achieved. The best performance of porous carbon for a Li-ion battery anode is obtained at the optimal temperature of 680 °C. Owing to the well-balanced soft and hard carbon compositions in the material, this porous carbon exhibits a high reversible capacity of 1440 mA h g-1 and excellent rate performance.

Conjugated polymer-based carbonaceous films as binder-free carbon electrodes in supercapacitors

We present a facile preparation method for carbonaceous film electrodes using poly(3,4-ethylenedioxythiophene) (PEDOT) and polyacetylene (PA) films as precursors via a morphology-retaining carbonization process. Carbonization was performed on acceptor-doped conjugated polymer films in the temperature range of 600–1100 °C. The obtained carbonaceous films had similar surface morphologies to those of the original conjugated polymer films. The carbonaceous film prepared from the electrochemically synthesized PEDOT film and the carbon film prepared from the chemically synthesized PA film showed hierarchical porous structures consisting of granular and fibril morphologies, respectively. The PEDOT and PA films carbonized at 1100 °C exhibited average electrical conductivities of 2.1 × 10⁰ S cm⁻¹ and 9.9 × 10¹ S cm⁻¹, respectively. The carbonaceous films could be used as binder-free carbon electrodes in supercapacitors, and the PEDOT-based carbonaceous film prepared in the range of 1000–1100 °C exhibited the most efficient performance on the basis of the electrochemical capacitance in neutral and alkaline aqueous solutions determined from cyclic voltammograms and galvanostatic charge/discharge curves. This approach requires no binders/additives and no further activation processes or additional treatments for the enhancement of the capacities of the carbon materials, enabling one-step fabrication and their direct use as carbon electrodes for energy-storage devices. This is the first report of PEDOT- and PA-based carbonaceous films being used as carbon electrodes in supercapacitors.

A facile preparation method for carbonaceous film electrodes was developed using conjugated polymer films as precursors via a morphology-retaining carbonization process.

Magnetic sulfur-doped porous carbon for preconcentration of trace mercury in environmental water prior to ICP-MS detection

A novel magnetic sulfur-doped porous carbon (MSPC) was fabricated via a simple one-step carbonization of a mixture of sucrose, basic magnesium sulfate whiskers and Fe₃O₄@SiO₂ nanoparticles.

Homogeneous sulphur-doped composites: porous carbon materials with unique hierarchical porous nanostructure for super-capacitor application

Homogeneous sulphur-doped porous carbon materials with a unique hierarchical porous nanostructure have been prepared by the combination of the two-dimensional interlayer confinement effect of a layered double hydroxide (LDH) and KOH activation method.

Doped graphene supercapacitors

Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.