An Ultra-microporous Carbon Material Boosting Integrated Capacitance for Cellulose-Based Supercapacitors

Porous Carbon Electrode Made of Biomass DNAs for High-Efficiency Quasi-Solid-State Supercapacitor

Since companies have declared their commitment to operating with 100% renewable energy, developing electrical storage systems using natural eco-friendly resources is in full swing. Efforts to replace existing materials in core electrode materials are accelerating, but the use of toxic chemicals in the complex production process is decreasing its value. This study presents a unique porous carbon electrode made of pure biomass DNA wastes synthesized simply via a single step of hydrogelation-calcination without activation through carbonization. Electrochemical analysis of the electrodes revealed energy storage performance with an outstanding specific capacitance of 563.34 F g-1 at 1 A g-1. The QSSC exhibited an energy density of 13.05 Wh kg-1 and a power density of 486.67 W kg-1. It was connected to a solar panel for renewable energy storage and successfully powered a digital clock and LEDs (Light Emitting Diode), demonstrating the potential of advanced sustainable and cost-effective energy storage solutions.

Natural bio-waste-derived 3D N/O self-doped heteroatom honeycomb-like porous carbon with tuned huge surface area for high-performance supercapacitor

Supercapacitor electrodes (SCs) of carbon-based materials with flexible structures and morphologies have demonstrated excellent electrical conductivity and chemical stability. Herein, a clean and cost-effective method for producing a 3D self-doped honeycomb-like carbonaceous material with KOH activation from bio-waste oyster shells (BWOSs) is described. A remarkable performance was achieved by the excellent hierarchical structured carbon (HSC-750), which has a large surface area and a reasonably high packing density. The enhanced BWOSs-derived HSC-750 shows an ultrahigh specific capacitance of 525 F/g at 0.5 A g-1 in 3 M KOH electrolyte, as well as high specific surface area (2377 m2 g-1), pore volume (1.35 cm3 g-1), nitrogen (4.70%), and oxygen (10.58%) doping contents. The SCs also exhibit exceptional cyclic stability, maintaining 98.5% of their capacitance after 10,000 charge/discharge cycles. The two-electrode approach provides a super high energy density of 28 Wh kg-1 at a power density of 250 W kg-1 in an alkaline solution, with remarkable cyclability after 10,000 cycles. The study demonstrates the innovative HSC synthesis from BWOSs precursor and cost-effective fabrication of 3D N/O self-doped heteroatom HSC for flexible energy storage.

Disclosing the intrinsic nature of efficient removal of antibiotics in N/S dual-doped porous carbon-based materials: The manipulation of internal electric field

N/S co-doping has emerged as a prevailing strategy for carbon-based adsorbents to facilitate the antibiotic removal efficiency. Nevertheless, the underlying interplay among N, S, and their adjacent vacancy defects remains overlooked. Herein, we present a novel in situ strategy for fabricating pyridinic-N dominated and S dual-doped porous carbon adsorbent with rich vacancy defects (VNSC). The experimental results revealed that N (acting as the electron donor) and S (acting as the electron acceptor) form an internal electric field (IEF), with a stronger IEF generated between pyridinic-N and S, while their adjacent vacancy defects activate carbon π electrons, thus enhancing the charge transfer of the IEF. Density functional theory (DFT) calculations further demonstrated that the rich charge transfer in the IEF facilitated the π-π electron donor-acceptor (EDA) interaction between VNSC and tetracycline (TC) as well as norfloxacin (NOR), and thus is the key to adsorption performance of VNSC. Consequently, VNSC exhibited high adsorption capacities toward TC (573.1 mg g-1) and NOR (517.0 mg g-1), and its potential for environmental applications was demonstrated by interference, environmentally relevant concentrations, fixed-bed column, and regeneration tests. This work discloses the natures of adsorption capacity for N/S dual-doped carbon-based materials for antibiotics.

Broadband electromagnetic wave absorption using pure carbon aerogel by synergistically modulating propagation path and carbonization degree

Carbon materials were widely used as electromagnetic (EM) wave absorption due to their advantages of light weight, environmental resistance and high electrical conductivity. However, conventional means were typically available by combining carbon and other materials to achieve effective absorption. Herein, a novel strategy using pure carbon aerogel with oriented structure was reported to enhance the EM wave absorption by synergistically modulating the wave propagation path and carbonization degree. The aerogel contained proposed modified carbon nanofibers (MCNF) derived from bacterial cellulose (BC), and core-shell carbon nanofibers @ reduced oxide graphene (CNF@RGO). The oriented structure was induced by the temperature field, which manifests anisotropic EM constitutive parameters (εx ≠ εz) at different directions of incident wave. The carbonization degree was adjusted by varying the carbonization temperature. At the carbonization temperature of 700 °C, the maximum reflection loss and effective absorption bandwidth reached -53.94 dB and 7.14 GHz, respectively, enabling the aerogel to outperform its previous counterparts. To clarify the EM wave mode-of-action in conjunction, physical models of the aerogel were established in addition to finite element simulation and theoretical analysis. Notably, the aerogel with a density of 3.6 mg/cm3 featured ultra-light weight, superhydrophobicity, superior compressibility, and thermal insulation. Our work offers an efficient strategy for designing broadband and multifunctional EM wave absorption materials (EWAMs), promising great potentials in complex stealth equipment.

Recent advances in biopolymers-based carbon materials for supercapacitors

Supercapacitors as potential candidates for novel green energy storage devices demonstrate a promising future in promoting sustainable energy supply, but their development is impeded by limited energy density, which can be addressed by developing high-capacitance electrode materials with efforts. Carbon materials derived from biopolymers have received much attention for their abundant reserves and environmentally sustainable nature, rendering them ideal for supercapacitor electrodes. However, the limited capacitance has hindered their widespread application, resulting in the proposal of various strategies to enhance the capacity properties of carbon electrodes. This paper critically reviewed the recent research progress of biopolymers-based carbon electrodes. The advances in biopolymers-based carbon electrodes for supercapacitors are presented, followed by the strategies to improve the capacitance of carbon electrodes which include pore engineering, doping engineering and composite engineering. Furthermore, this review is summarized and the challenges of biopolymer-derived carbon electrodes are discussed. The purpose of this review is to promote the widespread application of biopolymers in the domain of supercapacitors.

Sustainable and Scalable Synthesis of 2D Ultrathin Hierarchical Porous Carbon Nanosheets for High-Performance Supercapacitor

2D carbon nanomaterials such as graphene, carbon nanosheets, and their derivatives, representing the emerging class of advanced multifunctional materials, have gained great research interest because of their extensive applications ranging from electrochemistry to catalysis. However, sustainable and scalable synthesis of 2D carbon nanosheets (CNs) with hierarchical architecture and irregular structure via a green and low-cost strategy remains a great challenge. Herein, prehydrolysis liquor (PHL), an industrial byproduct of the pulping industry, is first employed to synthesize CNs via a simple hydrothermal carbonization technique. After mild activation with NH4 Cl and FeCl3 , the as-prepared activated CNs (A-CN@NFe) display an ultrathin structure (≈3 nm) and a desirable specific surface area (1021 m2 g-1 ) with hierarchical porous structure, which enables it to be both electroactive materials and structural support materials in nanofibrillated cellulose/A-CN@NFe/polypyrrole (NCP) nanocomposite, and thus endowing nanocomposite with impressive capacitance properties of 2546.3 mF cm-2 at 1 mA cm-2 . Furthermore, the resultant all-solid-state symmetric supercapacitor delivers a satisfactory energy storage ability of 90.1 µWh cm-2 at 250.0 µW cm-2 . Thus, this work not only opens a new window for sustainable and scalable synthesis of CNs, but also offers a double profits strategy for energy storage and biorefinery industry.

Tailored Properties of Carbon for Supercapacitors by Blending Lignin and Cellulose to Mimic Biomass as Carbonaceous Precursor

KOH-activated carbon materials prepared from biomass-derived carbon source, cellulose and lignin, were compared. Mixtures of different ratios of cellulose and lignin were used to partially mimic biomass as carbon source. This allows tailoring and optimizing of the KOH activated carbon materials by getting rid of the restriction of the intrinsic proportion of cellulose and lignin in specific biomass. The results indicate that cellulose use results in a more porous structure, whereas lignin use leads to more partially activated graphite structure. The activated carbon material (CL1) prepared from blend of cellulose with lignin in mass ratio of 1 : 1 exhibits a high specific surface area of 2000.39 m2  g-1 , and in TEABF4 /ACN (tetraethylammonium tetrafluoroborate dissolved in acetonitrile) electrolyte it showed a maximum specific capacitance of 136.10 F g-1 , a maximum energy density of 18.11 Wh kg-1 , and a capacitance retention of 85.04 % under current density as high as 15 A g-1 .

Nitrogen-Doped Hierarchical Porous Carbon Derived from Coal for High-Performance Supercapacitor

The surface properties and the hierarchical pore structure of carbon materials are important for their actual application in supercapacitors. It is important to pursue an integrated approach that is both easy and cost-effective but also challenging. Herein, coal-based hierarchical porous carbon with nitrogen doping was prepared by a simple dual template strategy using coal as the carbon precursor. The hierarchical pores were controlled by incorporating different target templates. Thanks to high conductivity, large electrochemically active surface area (483 m² g^-1), hierarchical porousness with appropriate micro-/mesoporous channels, and high surface nitrogen content (5.34%), the resulting porous carbon exhibits a high specific capacitance in a three-electrode system using KOH electrolytes, reaching 302 F g^-1 at 1 A g^-1 and 230 F g^-1 at 50 A g^-1 with a retention rate of 76%. At 250 W kg^-1, the symmetrical supercapacitor assembled at 6 M KOH shows a high energy density of 8.3 Wh kg^-1, and the stability of the cycling is smooth. The energy density of the symmetric supercapacitor assembled under ionic liquids was further increased to 48.3 Wh kg^-1 with a power output of 750 W kg^-1 when the operating voltage was increased to 3 V. This work expands the application of coal-based carbon materials in capacitive energy storage.

Electron and ion transport behavior of Vanadium based MXene induced by pressure for Lithium ion intercalated electrodes

Pressure, analogous with temperature and composition, is other meaningful variant for tuning the structure-activity properties of layered materials. In-situ high-pressure electrical results discover that Vanadium based MXene (V₂CT_x MXene) conductivity is increased by one order of magnitude from ambient to 10.4 GPa, and then the conductivity is still fixated on meeting growth as pressure releasing. Increased carrier concentration due to denser compactness is the most important factor in improving sample conductivity. Furthermore, abundant of V₂CT_x samples after preloading different pressures are prepared by the mean of the double-anvil hydraulic press for the first time, and results of increased conductivity were reproduced at ambient conditions. The first-principles calculation of V₂C (non-functional group), V₂CF, V₂CO, and V₂COH explains for the lattice expansion by tracing emotion of different function groups upon decompression. Electrochemical results obtain that once forming V₂CT_x MXene anode rapidly quenched from 2.0 GPa in hydraulic press shows better performance, obviously weakening electric polarization and increasing Li-ion transport rate due to its proper interlaminar densification and improved conductivity. This work opens up a new, simple, and universal approach to develop MXene materials with superior electrical and electrochemical properties, as well as expanding the potential applications for energy storage.

Pushing the Electrochemical Performance Limits of Polypyrrole Toward Stable Microelectronic Devices

Conducting polymers have achieved remarkable attentions owing to their exclusive characteristics, for instance, electrical conductivity, high ionic conductivity, visual transparency, and mechanical tractability. Surface and nanostructure engineering of conjugated conducting polymers offers an exceptional pathway to facilitate their implementation in a variety of scientific claims, comprising energy storage and production devices, flexible and wearable optoelectronic devices. A two-step tactic to assemble high-performance polypyrrole (PPy)-based microsupercapacitor (MSC) is utilized by transforming the current collectors to suppress structural pulverization and increase the adhesion of PPy, and then electrochemical co-deposition of PPy-CNT nanostructures on rGO@Au current collectors is performed. The resulting fine patterned MSC conveyed a high areal capacitance of 65.9 mF cm-2 (at a current density of 0.1 mA cm-2), an exceptional cycling performance of retaining 79% capacitance after 10,000 charge/discharge cycles at 5 mA cm-2. Benefiting from the intermediate graphene, current collector free PPy-CNT@rGO flexible MSC is produced by a facile transfer method on a flexible substrate, which delivered an areal capacitance of 70.25 mF cm-2 at 0.1 mA cm-2 and retained 46% of the initial capacitance at a current density of 1.0 mA cm-2. The flexible MSC is utilized as a skin compatible capacitive micro-strain sensor with excellent electromechanochemical characteristics.

In-situ construction of nitrogen-doped reduced graphene oxide@carbon nanofibers towards the synergetic enhancement of their microwave absorption properties via integrating point defects and structure engineering

The aim of this work is to develop materials that can absorb microwave to meet the requirements of stealth technology and solve the problem of electromagnetic pollution. However, the challenge is having materials with high-efficient absorption properties at an ultralow filling rate and visualizing the microwave response. The strategy used in this work was to integrate point defect and microstructure in preparing materials, nitrogen-doped reduced graphene oxide@ carbon nanofibers with high-efficient microwave absorption and double-layered structure. Ethylenediamine (nitrogen source), was doped into the materials, resulting in the generation of the defects. The microwave absorption performance of the materials was affected by the degree of defects due to the dipole polarization loss and conductive loss. The optimal samples gained the maximum reflection loss of -54.7 dB and effective absorption bandwidth of 4.74 GHz at a filling rate of only 8 wt%. More significantly, the microwave absorbing mechanism was analyzed visually in the response field. Furthermore, the actual stealth effects were evaluated by the radar cross section reduction, and the value was 29.2 dBm². The experimental results illustrated that nitrogen-doped reduced graphene oxide@ carbon nanofibers may be alternative materials with high microwave absorption performance at a low filling rate.

N self-doped hierarchically porous carbon derived from biomass as an efficient adsorbent for the removal of tetracycline antibiotics

In this study, we developed a simple strategy to synthesize a N self-doped hierarchically porous carbon adsorbent (LPC-NC) derived from biomass using potassium oxalate monohydrate and calcium carbonate and remove tetracyclines that are major antibiotics frequently measured in surface water. In the pyrolysis process, the N-enriching lotus seed pots biomass decomposed and formed a porous carbon matrix with self-doped N. The LPC-NC displayed high adsorption amount (506.6 mg/g for tetracycline (TTC) and 445.3 mg/g for oxytetracycline (OTC)), short equilibrium time (30 min) and stable reusability (the decline efficiency<8.0% after five cycles). Batch adsorption experimental and theoretical studies showed that the high adsorption capacity of LPC-NC for tetracyclines was mainly ascribed to the self-doped pyridinic-N species and the adsorption capacity of pyridinic-N species at the edge location was better than that of pyridinic-N species at the vacancy location. Importantly, we believe that the high adsorption performance of LPC-NC for tetracyclines is due to the activation of carbon π electrons by destroying the integrity of conjugation on LPC-NC, thus enhancing the π-π interaction between LPC-NC and tetracyclines. In addition, the results of solid-state nuclear magnetic resonance (NMR) confirmed that the hierarchically porous structure of LPC-NC was conducive to the adsorption of tetracyclines. These insights provide new ideas for the rational design of N-doped carbon-based adsorbents for the efficient removal of tetracyclines.

Cellulose Nanopaper: Fabrication, Functionalization, and Applications

Cellulose nanopaper has shown great potential in diverse fields including optoelectronic devices, food packaging, biomedical application, and so forth, owing to their various advantages such as good flexibility, tunable light transmittance, high thermal stability, low thermal expansion coefficient, and superior mechanical properties. Herein, recent progress on the fabrication and applications of cellulose nanopaper is summarized and discussed based on the analyses of the latest studies. We begin with a brief introduction of the three types of nanocellulose: cellulose nanocrystals, cellulose nanofibrils and bacterial cellulose, recapitulating their differences in preparation and properties. Then, the main preparation methods of cellulose nanopaper including filtration method and casting method as well as the newly developed technology are systematically elaborated and compared. Furthermore, the advanced applications of cellulose nanopaper including energy storage, electronic devices, water treatment, and high-performance packaging materials were highlighted. Finally, the prospects and ongoing challenges of cellulose nanopaper were summarized.

Biomass derived functional carbon materials for supercapacitor applications

Biochar produced from the thermochemical conversion of biomass, provides a green and sustainable platform for the preparation of various functional carbon materials (porous carbon, heteroatom doped biochar, carbon nanotubes, graphene, carbon quantum dots, etc.) towards advanced application. Their preparation involves the physical as well as chemical activation of biochar or directly from the biomass. The inherent versatile physicochemical properties of these versatile materials have been explored for the construction of the electrochemical energy storage devices like supercapacitors. In the present review, the various methodologies for the preparation of various biomass-derived carbon materials are summarized. Further utilization of these materials in supercapacitor electrodes and the properties associated with their charge storage ability, along with associated challenges and perspectives are also discussed.

Ultra-Stable Potassium Ion Storage of Nitrogen-Doped Carbon Nanofiber Derived from Bacterial Cellulose

As a promising energy storage system, potassium (K) ion batteries (KIBs) have received extensive attention due to the abundance of potassium resource in the Earth's crust and the similar properties of K to Li. However, the electrode always presents poor stability for K-ion storage due to the large radius of K-ions. In our work, we develop a nitrogen-doped carbon nanofiber (N-CNF) derived from bacterial cellulose by a simple pyrolysis process, which allows ultra-stable K-ion storage. Even at a large current density of 1 A g-1, our electrode exhibits a reversible specific capacity of 81 mAh g-1 after 3000 cycles for KIBs, with a capacity retention ratio of 71%. To investigate the electrochemical enhancement performance of our N-CNF, we provide the calculation results according to density functional theory, demonstrating that nitrogen doping in carbon is in favor of the K-ion adsorption during the potassiation process. This behavior will contribute to the enhancement of electrochemical performance for KIBs. In addition, our electrode exhibits a low voltage plateau during the potassiation-depotassiation process. To further evaluate this performance, we calculate the "relative energy density" for comparison. The results illustrate that our electrode presents a high "relative energy density", indicating that our N-CNF is a promising anode material for KIBs.

High-Performance and High-Voltage Supercapacitors Based on N-Doped Mesoporous Activated Carbon Derived from Dragon Fruit Peels

Designing the mesopore-dominated activated carbon electrodes has witnessed a significant breakthrough in enhancing the electrolyte breakdown voltage and energy density of supercapacitors. Herein, we designed N-doped mesoporous-dominated hierarchical activated carbon (N-dfAC) from the dragon fruit peel, an abundant biomass precursor, under the synergetic effect of KOH as the activating agent and melamine as the dopant. The electrode with the optimum N-doping content (3.4 at. %) exhibits the highest specific capacitance of 427 F g-1 at 5 mA cm-2 and cyclic stability of 123% capacitance retention until 50000 charge-discharge cycles at 500 mA cm-2 in aqueous 6 M KOH electrolytes. We designed a 4 V symmetric coin cell supercapacitor cell, which exhibits a remarkable specific energy and specific power of 112 W h kg-1 and 3214 W kg-1, respectively, in organic electrolytes. The cell also exhibits a significantly higher cycle life (109% capacitance retention) after 5000 GCD cycles at the working voltage of ≥3.5 V than commercial YP-50 AC (∼60% capacitance retention). The larger Debye length of the diffuse ion layer permitted by the mesopores can explain the higher voltage window, and the polar N-doped species in the dfAC enhance capacitance and ion transport. The results endow a new path to design high-capacity and high-working voltage EDLCs from eco-friendly and sustainable biomass materials by properly tuning their pore structures.

An Overview of Bacterial Cellulose in Flexible Electrochemical Energy Storage

The emerging generation of flexible energy storage devices has accelerated the research pace in terms of new materials, new processing techniques, and new designs that can meet the demands of mechanical stability upon bending or stretching at an acceptable cost, without compromising their electrochemical performance. Among the materials currently explored, biomass-derived materials have received extensive attention, because they are renewable, low in cost, earth-abundant and structurally diverse. This review is focused on fundamentals and applications of the bio-derived material bacterial cellulose (BC) in flexible electrochemical energy storage systems. Specifically, recent advances are summarized in the utilization of BC in stretchable substrates, carbonaceous species, and scaffolds for flexible core component construction. Finally, several perspectives related to BC-based materials for flexible electrochemical energy storages are proposed, aiming to provide possible future research directions in these fields.