Facile and friendly preparation of N/S Co-doped graphene-like carbon nanosheets with hierarchical pore by molten salt for all-solid-state supercapacitor

Synthesis of Co/Co3O4 Heterostructure in N-Doped Porous, Amorphous Carbon: A Superior Electrochemical Sensor for Sensitive Determination of Alectinib in Various Fluids

Highly crystallized Co and Co3O4 nanoparticles embedded in an N-doped amorphous carbon matrix have been successfully fabricated by the molten-salt-assisted method using KClO3 and zeolitic imidazolate framework-12 (ZIF-12). Pyrolysis of ZIF-12 with different concentrations of KClO3 leads to embedded Co and Co3O4 nanoparticles in a conductive amorphous carbon network. The impact of salt concentration on the morphology and electrochemical performance of these composites was investigated for electrochemical sensor applications. By employing a straightforward and efficient technique, Co/Co3O4 heterostructures were successfully synthesized in N-doped porous amorphous carbon. The Co/Co3O4 carbon heterostructures were optimized by varying the salt concentration, resulting in a significant electrochemical sensor performance for detecting ALC in both bulk and biological fluids. The sensor demonstrates excellent sensitivity (62.97 nmol/L) and selectivity toward ALC, with a wide linear range (0.2-2 μM) and a low detection limit (18.89 nM). Furthermore, it displays remarkable stability and reproducibility, positioning it as a strong contender for practical use in pharmaceutical analysis and biomedical research. This study presents a significant advancement in electrochemical sensing technology and underscores the potential of Co/Co3O4 heterostructures in the development of high-performance sensors for detecting bioactive compounds in complex matrices.

Single-Atom Co─O4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H2O2 Electrosynthesis

The production of hydrogen peroxide (H2O2) via the two-electron electrochemical oxygen reduction reaction (2e- ORR) is an essential alteration in the current anthraquinone-based method. Herein, a single-atom Co─O4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O4@PC). The Co─O4@PC electrocatalyst shows promising potential in H2O2 electrosynthesis via 2e- ORR, providing a high H2O2 selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating H2O2. In situ surface-sensitive attenuated total reflection Fourier transform infrared spectra and density functional theory calculations reveal that the electronic and geometric modification of Co─O4 induced by defective carbon sites result in decreased d-band center of Co atoms, providing the optimum adsorption energies of OOH* intermediate. The H-cell and flow cell assembled using Co─O4@PC as the cathode present long-term stability and high efficiency for H2O2 production. Particularly, a high H2O2 production rate of 0.25 mol g-1 cat h-1 at 0.6 V can be obtained by the flow cell. The in situ-generated H2O2 can promote the degradation of rhodamine B and sterilize Staphylococcus aureus via the Fenton process. This work can pave the way for the efficient production of H2O2 by using Co─O4 single atom electrocatalyst and unveil the electrocatalytic mechanism.

A state-of-the-art review on biomass-derived carbon materials for supercapacitor applications: From precursor selection to design optimization

Biomass-derived carbon materials have the characteristics of a wide range of precursor sources, controllable carbon nano-dimension, large specific surface area and abundant heteroatoms doping. At present, biomass-derived carbon materials have been widely used in electrochemical energy storage devices, especially the research and development of biomass-derived carbon materials for supercapacitors has become mature and in-depth. Therefore, it is of importance to summarize the advanced technologies and strategies for optimizing biomass-derived carbon materials for supercapacitors, which will effectively promote the further development of high-performance supercapacitors. In this review, the recent research progress of biomass-derived carbon materials is provided in detail, including the selection of biomass precursors, the design of carbon nano-dimension and the theory of heteroatom doping. Besides, the preparation methods of biomass-derived carbon materials and the related processes of optimizing the electrochemical performance are also summarized. This review ends with the perspectives for future research directions and challenges in the field of biomass-derived carbon materials for electrochemical applications. This review aims to provide helpful reference information for the nano-dimensional design and electrochemical performance optimization of biomass-derived carbon materials for the practical application of supercapacitors.

Novel Structural Design and Adsorption/Insertion Coordinating Quasi-Metallic Na Storage Mechanism toward High-performance Hard Carbon Anode Derived from Carboxymethyl Cellulose

Hard Carbon have become the most promising anode candidates for sodium-ion batteries, but the poor rate performance and cycle life remain key issues. In this work, N-doped hard carbon with abundant defects and expanded interlayer spacing is constructed by using carboxymethyl cellulose sodium as precursor with the assistance of graphitic carbon nitride. The formation of N-doped nanosheet structure is realized by the CN• or CC• radicals generated through the conversion of nitrile intermediates in the pyrolysis process. This greatly enhances the rate capability (192.8 mAh g-1 at 5.0 A g-1 ) and ultra-long cycle stability (233.3 mAh g-1 after 2000 cycles at 0.5 A g-1 ). In situ Raman spectroscopy, ex situ X-ray diffraction and X-ray photoelectron spectroscopy analysis in combination with comprehensive electrochemical characterizations, reveal that the interlayer insertion coordinated quasi-metallic sodium storage in the low potential plateau region and adsorption storage in the high potential sloping region. The first-principles density functional theory calculations further demonstrate strong coordination effect on nitrogen defect sites to capture sodium, especially with pyrrolic N, uncovering the formation mechanism of quasi-metallic bond in the sodium storage. This work provides new insights into the sodium storage mechanism of high-performance carbonaceous materials, and offers new opportunities for better design of hard carbon anode.

Heteroatom Codoped Graphene: The Importance of Nitrogen

Although graphene has exceptional properties, they are not enough to solve the extensive list of pressing world problems. The substitutional doping of graphene using heteroatoms is one of the preferred methods to adjust the physicochemical properties of graphene. Much effort has been made to dope graphene using a single dopant. However, in recent years, substantial efforts have been made to dope graphene using two or more dopants. This review summarizes all the hard work done to synthesize, characterize, and develop new technologies using codoped, tridoped, and quaternary doped graphene. First, I discuss a simple question that has a complicated answer: When can an atom be considered a dopant? Then, I briefly discuss the single atom doped graphene as a starting point for this review's primary objective: codoped or dual-doped graphene. I extend the discussion to include tridoped and quaternary doped graphene. I review most of the systems that have been synthesized or studied theoretically and the areas in which they have been used to develop new technologies. Finally, I discuss the challenges and prospects that will shape the future of this fascinating field. It will be shown that most of the graphene systems that have been reported involve the use of nitrogen, and much effort is needed to develop codoped graphene systems that do not rely on the stabilizing effects of nitrogen. I expect that this review will contribute to introducing more researchers to this fascinating field and enlarge the list of codoped graphene systems that have been synthesized.

Ultra-thin graphene cube framework@TiO2 heterojunction as high-performance anode materials for lithium ion batteries

Here, we proposed a new strategy to build the integrated graphene cube (Gr) framework@TiO₂ composite to improve the ion transport kinetics and electrical conductivity of TiO₂ as a long-life and high-capacity anode for lithium ion batteries. Combined with the salt template method for ultra-thin framework, the distinct structure of Gr@TiO₂ shows an excellent electrochemical performance, e.g., initial coulombic efficiency (ICE), rate performance and specific capacity, due to the increased kinetics of lithium ions. Through this method, the integrity is dramatically improved and the pulverization and agglomeration of the anode after long-term cycles are restrained. The optimized Gr@TiO₂ displays a high stable reversible capacity of 179.5 mAh g^-1 after 4000 cycles at 1 A g^-1, excellent rate performance (125.5 mAh g^-1 at 5 A g^-1). Kinetic studies through Electrochemical Impedance Spectra, Galvanostatic Intermittent Titration Technique and Linear Sweep Voltammetry confirm that the electrical conductivity and ion transport kinetics are dramatically improved through the ultra-thin graphene cube framework as a heterojunction structure of Gr@TiO₂.

An improved bioinspired strategy to construct nitrogen and phosphorus dual-doped network porous carbon with boosted kinetics potassium ion capacitors

Potassium-ion capacitors (PICs) have drawn appreciable attention because PICs can masterly integrate the virtues of the high energy density of battery-type anode and high power density of capacitor-type cathode. However, the sanguine scenario involves the incompatible capacity and sluggish kinetics in the PIC device. Herein, we report the synthesis of nitrogen and phosphorus-doped network porous carbon materials (NPMCs) via a self-sacrifice template strategy, which possesses a desired three-dimensional structure and prosperous electrochemical properties for K⁺ storage capacity. The obtained hierarchical porous carbon delivers a high reversible capacity of 420 mA h g^-1 at 0.05 A g^-1 and good cycling performance owing to its high concentration of reversible carbon defects and strong charge transfer kinetics. As expected, an advanced PIC device was assembled with a working voltage as high as 4.5 V, delivering an extraordinary energy density of 81.6 W h kg^-1 as well as a splendid long life. Systematic characterization analysis combined with density functional theory calculations indicates that the strategy for preparing PIC devices with outstanding performance in this work can provide new insights for the development of PICs for an extensive range of applications.

Multi-heteroatom-doped carbocatalyst as peroxymonosulfate and peroxydisulfate activator for water purification: A critical review

Catalytic activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) (or collectively known as persulfate, PS) using carbocatalyst is increasingly gaining attention as a promising technology for sustainable recalcitrant pollutant removal in water. Single heteroatom doping using either N, S, B or P is widely used to enhance the performance of the carbocatalyst for PS activation. However, the performance enhancement from single heteroatom doping is limited by the type of heteroatom used. To further enhance the performance of the carbocatalyst beyond the limit of single heteroatom doping, multi-heteroatom doping can be conducted. This review aims to provide a state-of-the-art overview on the development of multi-heteroatom-doped carbocatalyst for PS activation. The potential synergistic and antagonistic interactions of various heteroatoms including N and B, N and S, N and P, and N and halogen for PS activation are evaluated. Thereafter, the preparation strategies to develop multi-heteroatom-doped carbocatalyst including one-step and multi-step preparation approaches along with the characterization techniques are discussed. Evidence and summary of the performance of multi-heteroatom-doped carbocatalyst for various recalcitrant pollutants removal via PS activation are also provided. Finally, the prospects of employing multi-heteroatom-doped carbocatalyst including the need to study the correlation between different heteroatom combination, surface moiety type, and amount of dopant with the PS activation mechanism, identifying the best heteroatom combination, improving the durability of the carbocatalyst, evaluating the feasibility for full-scale application, developing low-cost multi-heteroatom-doped carbocatalyst, and assessing the environmental impact are also briefly discussed.

Removal of flue gas mercury by porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt medium

Porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt (LiCl-KCl) medium were employed for Hg⁰ removal. The carbons derived from molten salt carbonization (MSC) displayed much superior Hg⁰ removal performance comparing with the carbons derived from N₂ pyrolysis method (NC). The best molar ratio of LiCl-KCl was 59:41, the optimal molten salt temperature was 700 °C, and the best mass ratio of wood sawdust to molten salt was 1:10. The MSC displayed good applicability at 50-125 °C. The saturation Hg⁰ adsorption capacity of MSC was about 7828.39 μg·g^-1, far exceeding those for carbonaceous adsorbents reported in literatures. A Hg⁰ removal mechanism over MSC was proposed, i.e., the hierarchical porous structure accelerated mass transfer of Hg⁰, and the CO groups served as electron acceptors from Hg⁰ atoms to form organic matter bonded mercury (Hg-OM). The molten salt could be easily separated from the mixture of MSC for recycling multiple times. Thus, molten salt carbonization method appears to be promising in one-pot carbonization and activation of biomass as efficient adsorbents for gaseous Hg⁰.

Hydrogen-bonded frameworks crystals-assisted synthesis of flower-like carbon materials with penetrable meso/macropores from heavy fraction of bio-oil for Zn-ion hybrid supercapacitors

The application of biomass-based carbon materials in electrode materials are usually subject to their deficient adsorption sites as well as sluggish diffusion of electrolyte ions. Herein, flower-like carbons are obtained from the heavy fraction of bio-oil with the auxiliary of Hydrogen-bonded frameworks (HOFs) crystals. During the co-carbonization of the both, the HOFs crystals are removed on account of its poor stability, which directs the formation of flower-like morphology and generates the penetrable meso/macropores across petal-like carbon nanosheets. In addition, the pyrolysis gases serve as the agents for activation to enrich the active sites without the further activation. The degree of graphitization and the contents of pyridine nitrogen for carbon materials could be flexibly adjusted with the contents of HOFs. Owing to the beneficial 3D flower-like structure, high specific surface area (1076 m²/g), large pore volume (2.59 cm³/g), and rational N species, the assembled Zn//BH-4 hybrid supercapacitor reaches a superior energy density of 117.5 Wh/kg at 890 W/kg and maintains 60.7 Wh/kg even at 16.2 kW/kg.

Sulfur vacancies enriched Nickel-Cobalt sulfides hollow spheres with high performance for All-Solid-State hybrid supercapacitor

To pursue excellent performance of supercapacitor, an electrode material with designed morphology and tailored intrinsic properties is indeed desired. Herein, nickel-cobalt sulfides hollow spheres decorated with rich sulfur vacancies r-NiCo₂S₄ HSs) are prepared via an anion exchange of Ni-Co coordination polymer spheres, combined with wet chemical reduction. The r-NiCo₂S₄ HSs sample delivers excellent performance as an electrode: it possesses a high specific capacity (763.5C g^-1 at 1 A/g), favorable cyclability (91.40% after 5000 cycles at 10 A/g) and rate capacity (522.68C g^-1 at 15 A/g). Additionally, an all-solid-state hybrid supercapacitor device, assembled with r-NiCo₂S₄ HSs as the positive electrode and N/S co-doped activated carbon nanosheets as the negative electrode, presents an excellent energy density of 50.76 Wh kg^-1 under 800 W kg^-1 and feasible stability. Thus, combining hollow structure with sulfur vacancies could not only increase more active sites and ensure sufficient redox reactions, but also enhance electronic conductivity, facilitate ions / electrons transport and shorten diffusion path, which could be regarded as a promising approach to develop electrode materials with outstanding performance.

Porous 3D graphene aerogel co-doped with nitrogen and sulfur for high-performance supercapacitors

Heteroatom-doped carbon materials with a high specific area, a well-defined porous structure is important to high-performance supercapacitors (SCs). Here, S and N co-doped three-dimensional porous graphene aerogel (NS-3DPGHs) have been synthesized in a facile and efficient self-assembly process with thiourea acting as the reducing and doping agent solution. Operating as a SC electrode, fabricated co-doping graphene, i.e. the sample of NS-3DPGH-150 exhibits the highest specific capacitance of 412.9 F g^-1 under 0.5 A g^-1 and prominent cycle stabilization with 96.4% capacitance retention in the back of 10 000 cycles. Furthermore, based on NS-3DPGH-150, the symmetrical supercapacitor as-prepared in 6 M KOH displays a superior energy density of 12.9 Wh kg^-1 under the power density of 249 W kg^-1. Hence, NS-3DPGHs could be considered as an excellent candidate for SCs.

Fabrication of high-performance symmetrical coin cell supercapacitors by using one step and green synthesis sulfur doped graphene powders

In this work, symmetrical supercapacitors in the form of coin cell types were produced by using S-doped graphene powders.

Insight into activated carbon from different kinds of chemical activating agents: A review

Activated carbon (AC) is an important material in various fields owing to its low cost, well-developed porosity, and favorable chemical stability. Key factors for the optimal synthesis of AC are the carbon precursors, activation pathways, activating agents, and design of the procedure parameters. So far, no case studies have reviewed the activating agents used during the chemical activation process. Accordingly, the present review provides a summary of recent research, highlighting the development of activating agents during the process of AC. Detailed lists of pore-forming mechanisms by various activating agents, including alkaline, acidic, neutral, and self-activating agents, have been systematically summarized. Furthermore, the effects of activating agents on the experimental procedures have also been established. Finally, a comprehensive discussion about the influences of activating agents on the physical and chemical properties of the resultant AC is included. The objective of this study is to reveal and distinguish the individual roles of different activating agents during AC synthesis.

One-step production of N-O-P-S co-doped porous carbon from bean worms for supercapacitors with high performance

In recent years, multi-heteroatom-doped hierarchical porous carbons (HPCs) derived from natural potential precursors and synthesized in a simple, efficient and environmentally friendly manner have received extensive attention in many critical technology applications. Herein, bean worms (BWs), a pest in bean fields, were innovatively employed as a precursor via a one-step method to prepare N-O-P-S co-doped porous carbon materials. The pore structure and surface elemental composition of carbon can be modified by adjusting KOH dosage, exhibiting a high surface area (S _BET) of 1967.1 m² g^-1 together with many surface functional groups. The BW-based electrodes for supercapacitors were shown to have a good capacitance of up to 371.8 F g^-1 in 6 M KOH electrolyte at 0.1 A g^-1, and good rate properties with 190 F g^-1 at a high current density of 10 A g^-1. Furthermore, a symmetric supercapacitor based on the optimal carbon material (BWPC_1/3) was also assembled with a wide voltage window of 2.0 V, demonstrating satisfactory energy density (27.5 W h kg^-1 at 200 W kg^-1) and electrochemical cycling stability (97.1% retention at 10 A g^-1 over 10 000 charge/discharge cycles). The facile strategy proposed in this work provides an attractive way to achieve high-efficiency and scalable production of biomass-derived HPCs for energy storage.