Recent Advancement of Nanostructured Carbon for Energy Applications

Designing ionic channels in novel carbons for electrochemical energy storage

Tremendous efforts have been dedicated to developing high-performance energy storage devices based on the micro- or nano-manipulation of novel carbon electrodes, as certain nanocarbons are perceived to have advantages such as high specific surface areas, superior electric conductivities, excellent mechanical properties and so on. In typical electrochemical electrodes, ions are intercalated/deintercalated into/from the bulk (for batteries) or adsorbed/desorbed on/from the surface (for electrochemical capacitors). Fast ionic transport, significantly determined by ionic channels in active electrodes or supporting materials, is a prerequisite for the efficient energy storage with carbons. In this report, we summarize recent design strategies for ionic channels in novel carbons and give comments on the promising features based on those carbons towards tailorable ionic channels.

Soft Hybrid Scaffold (SHS) Strategy for Realization of Ultrahigh Energy Density of Wearable Aqueous Supercapacitors

Future wearable electronics requires safe and high-energy-density supercapacitors (SCs). Commercial SCs making use of organic electrolytes show high energy density, but the flammability of the electrolyte raises serious safety concerns. Aqueous SCs, on the other hand, are very safe, but the energy density is low due to the much narrower voltage window and the difficulty of fabricating thick electrodes. A new materials strategy named soft hybrid scaffold (SHS), which allows easy buildup of ultrathick electrodes made of 3D porous pseudo-material-modified carbon networks, is reported. The carbon network provides excellent mechanical stability and electric conductivity, the hierarchically porous structures ensure rapid ionic transport, and the pseudomaterials enlarge the electrochemical window. Asymmetric aqueous SCs using SHS electrodes show higher energy density than both commercial organic SCs and literature-reported aqueous SCs, with good cycle life and mechanical flexibility. The aqueous SC device is tailorable, waterproof, and fire-retardant, representing a high safety toward practical applications.

Three-dimensional hierarchical ZnCo2O4@C3N4-B nanoflowers as high-performance anode materials for lithium-ion batteries

ZnCo₂O₄ has become one of the most widely used anode materials due to its good specific capacity, cost-efficiency, high thermal stability and environmental benignity.

Low-temperature synthesis of sp2 carbon nanomaterials

sp² carbon nanomaterials are mainly composed of sp²-hybridized carbon atoms in the form of a hexagonal network. Due to the π bonds formed by unpaired electrons, sp² carbon nanomaterials possess excellent electronic, mechanical, and optical properties, which have attracted great attention in recent years. As the advanced sp² carbon nanomaterials, graphene and carbon nanotubes (CNTs) have great potential in electronics, sensors, energy storage and conversion devices, etc. The low-temperature synthesis of graphene and CNTs are indispensable to promote the practical industrial application. Furthermore, graphene and CNTs can even be expected to directly grow on the flexible plastic that cannot bear high temperature, expanding bright prospects for applications in emerging flexible nanotechnology. An in-depth understanding of the formation mechanism of sp² carbon nanomaterials is beneficial for reducing the growth temperature and satisfying the demands of industrial production in an economical and low-cost way. In this review, we discuss the main strategies and the related mechanisms in low-temperature synthesis of graphene and CNTs, including the selection of precursors with high reactivity, the design of catalyst, and the introduction of additional energy for the pre-decomposition of precursors. Furthermore, challenges and outlooks are highlighted for further progress in the practical industrial application.

Preparation and Carbon-Dependent Supercapacitive Behaviour of Nanohybrid Materials between Polyoxometalate and Porous Carbon Derived from Zeolitic Templates

An electrochemical cell combining the energy storage characteristics of the chemical redox reaction and a physical capacitor effect presents advantages including high energy and power densities, and long durability. In this study, we prepared nanohybrid materials between polyoxometalate (POM) and porous carbon, which have different porous structures and pore sizes, using different zeolitic templates. The POM molecules were loaded inside the porous carbon, and these POM/carbon nanohybrid materials were used as cathode active materials for lithium–ion batteries (LIBs). The performance of these molecular cluster batteries (MCBs) was significantly dependent on the porous carbon. Operando X-ray absorption fine structure (XAFS) and ⁷Li solid-state nuclear magnetic resonance (NMR) measurements of the POM/carbon-MCBs revealed that three-dimensional porous carbon with high surface areas can improve the performance. The results highlight the remarkable performance of porous carbon with a three-dimensionally-linked pore network structure as an additive for supercapacitors to realise high-performance energy storage devices.

The Role of Functionalization in the Applications of Carbon Materials: An Overview

The carbon-based materials (CbMs) refer to a class of substances in which the carbon atoms can assume different hybridization states (sp1, sp2, sp3) leading to different allotropic structures -. In these substances, the carbon atoms can form robust covalent bonds with other carbon atoms or with a vast class of metallic and non-metallic elements, giving rise to an enormous number of compounds from small molecules to long chains to solids. This is one of the reasons why the carbon chemistry is at the basis of the organic chemistry and the biochemistry from which life on earth was born. In this context, the surface chemistry assumes a substantial role dictating the physical and chemical properties of the carbon-based materials. Different functionalities are obtained by bonding carbon atoms with heteroatoms (mainly oxygen, nitrogen, sulfur) determining a certain reactivity of the compound which otherwise is rather weak. This holds for classic materials such as the diamond, the graphite, the carbon black and the porous carbon but functionalization is widely applied also to the carbon nanostructures which came at play mainly in the last two decades. As a matter of fact, nowadays, in addition to fabrication of nano and porous structures, the functionalization of CbMs is at the basis of a number of applications as catalysis, energy conversion, sensing, biomedicine, adsorption etc. This work is dedicated to the modification of the surface chemistry reviewing the different approaches also considering the different macro and nano allotropic forms of carbon.

Studies on Possible Ion-Confinement in Nanopore for Enhanced Supercapacitor Performance in 4V EMIBF4 Ionic Liquids

Supercapacitors have the rapid charge/discharge kinetics and long stability in comparison with various batteries yet undergo low energy density. Theoretically, square dependence of energy density upon voltage reveals a fruitful but challenging engineering tenet to address this long-standing problem by keeping a large voltage window in the compositionally/structurally fine-tuned electrode/electrolyte systems. Inspired by this, a facile salt-templating enables hierarchically porous biochars for supercapacitors filled by the high-voltage ionic liquids (ILs). Resultant nanostructures possess a coherent/interpenetrated framework of curved atom-thick sidewalls of 0.8-/1.5-nanometer pores to reconcile the pore-size-dependent adlayer structures of ILs in nanopores. Surprisingly, this narrow dual-model pore matches ionic radii of selected ILs to accommodate ions by unique coupled nano-/bi-layer nanoconfinements, augmenting the degree of confinement (DoC). The high DoC efficiently undermines the coulombic ordering networks and induces the local conformational oscillations, thus triggering an anomalous but robust charge separation. This novel bi-/mono-layer nanoconfinement combination mediates harmful overscreening/overcrowding effects to reinforce ion-partitioning, mitigating long-lasting conflicts of power/energy densities. This interesting result differs from a long-held viewpoint regarding the sieving effect that ion-in-pore capacitance peaks only if pore size critically approaches the ion dimension. Optimal biocarbon finally presents a very high/stable operational voltage up to 4 V and specific energy/power rating (88.3 Whkg^-1 at 1 kWkg^-1, 47.7 Whkg^-1 albeit at a high battery-accessible specific power density of 20 kWkg^-1), overwhelmingly outperforming most hitherto-reported supercapacitors and some batteries. Such attractive charge storage level can preliminarily elucidate an alternative form of a super-ionic-state high-energy storage linked with both the coordination number and coulombic periodism of the few ion-sized mesopores inside carbon electrodes, escalating supercapacitors into a novel criterion of charge delivery.

High-Yield Continuous-Flow Synthesis of Spheroidal C60@Graphene Composites as Supercapacitors

Graphene spheres confining fullerene C₆₀ are quantitatively formed under high-shear and continuous-flow processing using a vortex fluidic device (VFD). This involves intense micromixing a colloidal suspension of graphite in DMF and an o-xylene solution of C₆₀ at room temperature in the absence of surfactants and other auxiliary substances. The diameters of the composite spheres, C₆₀@graphene, can be controlled with size distributions ranging from 1.5 to 3.5 μm, depending on the VFD operating parameters, including rotational speed, flow rate, relative ratio of C₆₀ to graphite, and the concentration of fullerene. An electrode of the composite material has high cycle stability, with a high areal capacitance of 103.4 mF cm^-2, maintaining its capacitances to 24.7 F g^-1 and 86.4 mF cm^-2 (83.5%) at a high scan rate of 100 mV s^-1.

N-Doped holey carbon materials derived from a metal-free macrocycle cucurbit[6]uril assembly as an efficient electrocatalyst for the oxygen reduction reaction

The first example of the preparation of nitrogen-doped holey carbon (NHC) with abundant in-plane holes derived from a rigid macrocycle cucurbit[6]uril self-assembly is reported. The NHC shows comparable activity, better stability and higher methanol tolerance towards the oxygen reduction reaction compared to the use of commercial Pt/C.

Controlled Design of a Robust Hierarchically Porous and Hollow Carbon Fiber Textile for High-Performance Freestanding Electrodes

For most carbon-based materials, hierarchical porous structure including well-defined macropores, mesopores, and micropores is commonly seen in 3D aerogels, monoliths, or some carbothermic natural biomass. However, because of the filiform character and long draw ratio, it is difficult to achieve such pore network as well as attain excellent mechanical performance in a 1D single carbon fiber system. To address this issue, an innovative hierarchical porous and hollow carbon textile (HPHCT) is developed via the "dynamic template (KOH, SiO2, and Al2O3) calcination" strategy. Unlike conventional one-step activated carbonized fiber simply with meso or micropores, the fabricated textile generates honeycomb-like macropores uniformly spreading on fiber surface. More importantly, the ultra-lightweight yet flexible HPHCT is mechanically robust, superior to ordinary carbonized one. In addition, it delivers high capacitance of maximum 220 F g-1 as well as keeping long term stability with 100% retention after 10 000 cycles as freestanding electrodes in supercapacitor. Meanwhile, the all-solid integrated symmetric HPHCT supercapacitors demonstrates its high potential in powering electronics for wearable energy storage application.

Hollow Carbon Nanospheres with Developed Porous Structure and Retained N Doping for Facilitated Electrochemical Energy Storage

Development of highly porous carbons with abundant surface functionalities and well-defined nanostructure is of significance for many important electrochemical energy storage systems. However, porous carbons suffer from a compromise between porosity, doped functionality, and nanostructure that have thus far restricted their performances. Here, we report the design of highly porous, nitrogen-enriched hollow carbon nanospheres (PN-HCNs) by an interfacial copolymerization strategy followed by NH₃-assisted carbonization, and further demonstrate their significance and effectiveness in enhancing the electrochemical performances. The PN-HCN simultaneously delivers a large surface area (1237 m² g^-1) and high N functionalities (6.25 atom %) with a remarkable efficiency of the surface area increase to N loss ratio enabled by NH₃ treatment while inheriting the hollow nanospherical structure. Accordingly, owing to the enhanced surface area and retained N doping, the prepared PN-HCN demonstrates outstanding electrochemical performances as a cathode host in lithium-sulfur batteries, including a near-to-theoretical capacity of 1620 mAh g^-1, high rate capability and good cycling stability (789 mAh g^-1 at 0.5C after 200 cycles). These results are superior to those of HCN without NH₃ treatment. Also, PN-HCN exhibits superior capacitances (203 F g^-1) and fast ion transport ability in supercapacitors. Our finding shows the simultaneous achievement of both highly porous structures and sufficient N functionalities for high-performance applications.

Deep-eutectic-solvent synthesis of N/O self-doped hollow carbon nanorods for efficient energy storage

N/O self-doped hollow carbon nanorods (HCNs) with micro/mesoporous walls are fabricated based on a new deep-eutectic-solvent that serves as an all-in-one precursor, self-template, and self-dopant agent. The carbon-based supercapacitor using an ionic liquid electrolyte exhibits a high energy density of 116.5 W h kg-1 with excellent long-term cycling performance.

Continuous flow photolytic reduction of graphene oxide

Reduced graphene oxide (rGO) is generated from GO dispersed in water under continuous flow in the absence of harsh reducing agents, in a vortex fluidic device, such that the processing is scalable with uniformity of the product. This involves simultaneously UV irradiating (λ = 254 nm, 20 W) the dynamic thin film in the rapidly rotating glass tube in the microfluidic platform. The rGO is comparable to that formed using waste generating chemical based processing, with a film of the material having a resistance of 2.2 × 105 Ω and a remarkably high conductivity of 2 × 104 S cm-1.

Three-step-in-one synthesis of supercapacitor MWCNT superparamagnetic magnetite composite material under flow

Composites of multi-walled carbon nanotubes (MWCNTs) and superparamagnetic magnetite nanoparticles, Fe₃O₄@MWCNT, were synthesized in DMF in a vortex fluidic device (VFD). This involved in situ generation of the iron oxide nanoparticles by laser ablation of bulk iron metal at 1064 nm using a pulsed laser, over the dynamic thin film in the microfluidic platform. The overall processing is a three-step in one operation: (i) slicing MWCNTs, (ii) generating the superparamagnetic nanoparticles and (iii) decorating them on the surface of the MWCNTs. The Fe₃O₄@MWCNT composites were characterized by transmission electron microscopy, scanning transmission electron microscope, TG analysis, X-ray diffraction and X-ray photoelectron spectroscopy. They were used as an active electrode for supercapacitor measurements, establishing high gravimetric and areal capacitances of 834 F g^-1 and 1317.7 mF cm^-2 at a scan rate of 10 mV s^-1, respectively, which are higher values than those reported using similar materials. In addition, the designer material has a significantly higher specific energy of 115.84 W h kg^-1 at a specific power of 2085 W kg^-1, thereby showing promise for the material in next-generation energy storage devices.

Temperature Characteristics of a Pressure Sensor Based on BN/Graphene/BN Heterostructure

Temperature is a significant factor in the application of graphene-based pressure sensors. The influence of temperature on graphene pressure sensors is twofold: an increase in temperature causes the substrates of graphene pressure sensors to thermally expand, and thus, the graphene membrane is stretched, leading to an increase in the device resistance; an increase in temperature also causes a change in the graphene electrophonon coupling, resulting in a decrease in device resistance. To investigate which effect dominates the influence of temperature on the pressure sensor based on the graphene–boron nitride (BN) heterostructure proposed in our previous work, the temperature characteristics of two BN/graphene/BN heterostructures with and without a microcavity beneath them were analyzed in the temperature range 30–150 °C. Experimental results showed that the resistance of the BN/graphene/BN heterostructure with a microcavity increased with the increase in temperature, and the temperature coefficient was up to 0.25%°C⁻¹, indicating the considerable influence of thermal expansion in such devices. In contrast, with an increase in temperature, the resistance of the BN/graphene/BN heterostructure without a microcavity decreased with a temperature coefficient of −0.16%°C⁻¹. The linearity of the resistance change rate (ΔR/R)–temperature curve of the BN/graphene/BN heterostructure without a microcavity was better than that of the BN/graphene/BN heterostructure with a microcavity. These results indicate that the influence of temperature on the pressure sensors based on BN/graphene/BN heterostructures should be considered, especially for devices with pressure microcavities. BN/graphene/BN heterostructures without microcavities can be used as high-performance temperature sensors.

Tunable photoluminescence from interconnected graphene network with potential to enhance the efficiency of a hybrid Si nanowire solar cell

An interconnected graphene network (IGN) structure with excellent photoluminescence (PL) properties was synthesized using a one-pot microwave-assisted hydrothermal carbonization route. The material exhibited intense and excitation-wavelength dependent PL emission located mainly in the UV-blue light range (300-450 nm). The result demonstrates that graphene networks could also be included in the emerging class of tunable PL carbon nanomaterials. Furthermore, we have taken a first step towards their incorporation into solar cell devices by fabricating IGN/p-SiNWs radial heterojunctions using the versatile potentiostatic electrodeposition technique. The IGN modified p-SiNW solar cell showed the best performance with an overall enhancement of power conversion efficiency of 7.5 times higher than the reference cell. We emphasize that the structural and electronic characteristics of the as-prepared IGN combined with tapering effects are directly responsible for the tripled short circuit current density and 9% improvement of open circuit voltage with respect to the reference cell. Finally, we have demonstrated that the IGN successfully passivated the Si nanowires' surface using intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS). These promising findings indicate that further IGN exploitation may help to gain efficiency in future energy conversion applications.

Recent Advances and Perspectives of Carbon-Based Nanostructures as Anode Materials for Li-ion Batteries

Rechargeable batteries are attractive power storage equipment for a broad diversity of applications. Lithium-ion (Li-ion) batteries are widely used the superior rechargeable battery in portable electronics. The increasing needs in portable electronic devices require improved Li-ion batteries with excellent results over many discharge-recharge cycles. One important approach to ensure the electrodes' integrity is by increasing the storage capacity of cathode and anode materials. This could be achieved using nanoscale-sized electrode materials. In the article, we review the recent advances and perspectives of carbon nanomaterials as anode material for Lithium-ion battery applications. The first section of the review presents the general introduction, industrial use, and working principles of Li-ion batteries. It also demonstrates the advantages and disadvantages of nanomaterials and challenges to utilize nanomaterials for Li-ion battery applications. The second section of the review describes the utilization of various carbon-based nanomaterials as anode materials for Li-ion battery applications. The last section presents the conclusion and future directions.

Ni(OH)2-decorated nitrogen doped MWCNT nanosheets as an efficient electrode for high performance supercapacitors

In this study, nickel hydroxide nanoparticles (NPs) decorated with nitrogen doped multiwalled carbon nanotubes (N-MWCNT) hybrid composite was synthesized by thermal reduction process in the presence of cetyl ammonium bromide (CTAB) and urea. The as-synthesized Ni(OH)₂@N-MWCNT hybrid composite was characterized by FTIR, Raman, XRD, BET, BJH and FE-TEM analyses. These prepared porous carbon hybrid composite materials possessed high specific surface area and sheet like morphology useful for active electrode materials. The maximum specific capacitance of Ni(OH)₂@N-MWCNT hybrid nanocomposite in the two electrode system showed 350 Fg⁻¹ at 0.5 A/g,energy density ~43.75 Wkg⁻¹ and corresponds to power density 1500 W kg⁻¹ with excellent capacity retention after 5000 cycles. The results suggest that the prepared two-dimensional hybrid composite is a promising electrode material for electrochemical energy storage applications.

Carbon-Nanomaterial-Based Flexible Batteries for Wearable Electronics

Wearable electronics have received considerable attention in recent years. These devices have penetrated every aspect of our daily lives and stimulated interest in futuristic electronics. Thus, flexible batteries that can be bent or folded are desperately needed, and their electrochemical functions should be maintained stably under the deformation states, given the increasing demands for wearable electronics. Carbon nanomaterials, such as carbon nanotubes, graphene, and/or their composites, as flexible materials exhibit excellent properties that make them suitable for use in flexible batteries. Herein, the most recent progress on flexible batteries using carbon nanomaterials is discussed from the viewpoint of materials fabrication, structure design, and property optimization. Based on the current progress, the existing advantages, challenges, and prospects are outlined and highlighted.

Advanced Carbon for Flexible and Wearable Electronics

Flexible and wearable electronics are attracting wide attention due to their potential applications in wearable human health monitoring and care systems. Carbon materials have combined superiorities such as good electrical conductivity, intrinsic and structural flexibility, light weight, high chemical and thermal stability, ease of chemical functionalization, as well as potential mass production, enabling them to be promising candidate materials for flexible and wearable electronics. Consequently, great efforts are devoted to the controlled fabrication of carbon materials with rationally designed structures for applications in next-generation electronics. Herein, the latest advances in the rational design and controlled fabrication of carbon materials toward applications in flexible and wearable electronics are reviewed. Various carbon materials (carbon nanotubes, graphene, natural-biomaterial-derived carbon, etc.) with controlled micro/nanostructures and designed macroscopic morphologies for high-performance flexible electronics are introduced. The fabrication strategies, working mechanism, performance, and applications of carbon-based flexible devices are reviewed and discussed, including strain/pressure sensors, temperature/humidity sensors, electrochemical sensors, flexible conductive electrodes/wires, and flexible power devices. Furthermore, the integration of multiple devices toward multifunctional wearable systems is briefly reviewed. Finally, the existing challenges and future opportunities in this field are summarized.

Biomass waste-derived nitrogen-rich hierarchical porous carbon offering superior capacitive behavior in an environmentally friendly aqueous MgSO4 electrolyte

Nitrogen-doped porous carbons have been extensively investigated to improve the specific capacitance in aqueous electrolytes by increasing the specific surface area and nitrogen content and by optimizing the pore structure. However, research on the effect of electrolyte cations on the specific capacitance of these materials is rare, especially for neutral electrolytes. Herein, a nitrogen-rich hierarchically porous carbon (NRHPC) with a high nitrogen content of 12.3 atm% is successfully prepared by pyrolyzing a mixture of bagasse, K₂CO₃ and urea in a mass ratio of 2:1:4. It is found that NRHPC shows superior electrochemical performance in MgSO₄ than in Li₂SO₄ electrolyte, with specific capacitances of 315.0, 274.4, and 188.1 F g^-1 at 1.0, 10.0, and 100 A g^-1, respectively. Furthermore, it is found that the capacitance enhancement is closely related to the nitrogen content of the porous carbon materials. Theoretical calculation reveals that the Mg²⁺ ions have higher affinity towards the N atoms than Li⁺, producing higher charge storage capability via interaction between the Mg²⁺ and N atoms. When the 1.0 M MgSO₄ is used as electrolyte, a symmetric capacitor based on the nitrogen-rich hierarchically porous carbon shows a high energy density of 39.5 Wh kg^-1 at a power density of 0.9 kW kg^-1. Moreover, this as-assembled device displays superior long-term cycling stability, with a capacitance retention of >96.2% after 10,000 cycles at 10.0 A g^-1.

Covalent Grafting of BPin functions on Carbon Nanotubes and Chan-Lam-Evans Post-Functionalization

The chemical functionalization of carbon nanotubes is often a prerequisite prior to their use in various applications. The covalent grafting of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (BPin) functional groups directly on the surface of multi- and single-walled carbon nanotubes, activated by nucleophilic addition of nBuLi, was carried out. Thermogravimetric analysis (TGA) coupled with mass spectrometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ions mass spectrometry (ToF-SIMS) confirmed the efficiency of this methodology and proved the integrity and covalent grafting of the BPin functional groups. These groups were further reacted with various nucleophiles in the presence of a copper(II) source in the conditions of the aerobic Chan-Lam-Evans coupling. The resulting materials were characterized by TGA, XPS and ToF-SIMS. This route is efficient, reliable and among the scarce reactions that enable the direct grafting of heteroatoms at carbonaceous material surfaces.

Porous carbon-NiO nanocomposites for amperometric detection of hydrazine and hydrogen peroxide

A hydrothermal route is reported for the preparation of a composite consisting of sheet-like glucose-derived carbon and nickel oxide nanoparticles. The nanocomposites were prepared at different annealing temperatures and exploited as electrode materials for amperometric (i-t) determination of hydrazine (N₂H₄) and hydrogen peroxide (H₂O₂) at trace levels. The performances of the sensors were assessed by cyclic voltammetry and amperometry detection using a rotating disk electrode (RDE) technique. The modified electrode annealed at ca. 300 °C was found to exhibit the best electrocatalytic performance in terms of sensitive and selective detection of N₂H₄ and H₂O₂ even in the presence of interfering species. The electrode is inexpensive, robust, easy to prepare in large batches, highly stable, and has a low overpotential. H₂O₂ can be sensed, best at a working voltage of typically 0.13 V vs Ag/AgCl; rotationg speed 1200 rpm) over a wide concentration range (0.01 to 3.9 µM) with a detection limit of 1.5 nM. N₂H₄ can be sensed, best at a working voltage of typically 0.0 V within the concentration range from 0.5 μM to 12 mM with an excellent detection limit of 1.5 µM. Thus, this cost-effective and robust modified electrode, which may be readily prepared in large batch quantity, represents a practical platform for industrial sensing. Graphical abstract Schematic of the hydrothermal method for synthesis of carbon and nickel oxide nanoparticle composites (GCD/NiO-150, GCD/NiO-300, and GCD/NiO-450). The composite was used for the electro-oxidation of hydrazine (N₂H₄) and hydrogen peroxide (H₂O₂) by cyclic voltammetry and amperometry (i-t).

Urea-assisted template-less synthesis of heavily nitrogen-doped hollow carbon fibers for the anode material of lithium-ion batteries

A unique decomposition pathway of urea involving gas evolution was exploited as a way to introduce voids and mesopores into one-dimensional carbon nanofibers.

Core–shell assembly of carbon nanofibers and a 2D conductive metal–organic framework as a flexible free-standing membrane for high-performance supercapacitors

A hybrid core–shell material based on carbon nanofibers and a 2D conductive metal–organic framework has been fabricated into a flexible free-standing membrane as an electrode material for supercapacitors.

Polymer network-derived nitrogen/sulphur co-doped three-dimensionally interconnected hierarchically porous carbon for oxygen reduction, lithium-ion battery, and supercapacitor

Rational design and simple synthesis of carbon-based materials with high electrocatalytic activity are essential for their practical applications in electrochemical energy conversion and storage devices. Herein, we report the synthesis of nitrogen, sulfur co-doped three-dimensional interconnected hierarchically porous carbon (NSHPC) by zinc acetate assisted pyrolysis of polymer networks. The thus-synthesized NSHPC has a specific surface area of 1057 cm² g⁻¹ with the coexistence of micro- and meso-pores. As metal-free electrocatalyst, the NSHPC exhibits a promising activity towards oxygen reduction reactions as evidenced by the slightly negative shift of half-wave potential compared with commercial Pt/C catalyst. The assembled lithium ion battery using NSHPC as anode delivers the reversible capacity of 740 and 470 mA h g⁻¹ at current densities of 2 and 5 A g⁻¹ without performance decay after 1000 charge–discharge cycles. Moreover, the assembled supercapacitor using NSHPC as electrode has the capacitance of 203 F g⁻¹ at 1 A g⁻¹.

Polymer networks are efficient precursors for large scale production of hierarchical porous carbon.

Efficacy beyond 17% via engineering the length and quality of grafts in organic halide perovskite/CNT photovoltaics

Pure CNTs and their derivatives grafted with the poly(3-dodecyl thiophene) (CNT-g-PDDT) and poly(3-hexylthiophene) (CNT-g-P3HT) polymers were employed to improve the morphological, optical, and photovoltaic properties of perovskite solar cells.

CFx primary batteries based on fluorinated carbon nanocages

The material with the fluorination level of x = 0.98 reaches the specific capacity of 850 mA h g⁻¹, i.e., its theoretical value.

Nitrogen-rich hierarchical porous carbon materials with interconnected channels for high stability supercapacitors

Novel nitrogen-rich hierarchical porous carbon (NPC) materials have been successfully synthesized using eggshells as the template and activation agent.

A Conductive and Highly Deformable All-Pseudocapacitive Composite Paper as Supercapacitor Electrode with Improved Areal and Volumetric Capacitance

Flexible energy storage electronics have gained increasing attention in recent years, but the simultaneous acquiring of high volumetric and high areal capacities as well as excellent flexibility in order to truly implement wearable and portable electronics in practice remains challenging. Here, a conductive and highly deformable freestanding all-pseudocapacitive paper electrode (Ti₃ C₂ T_x /MnO₂ NWs) is fabricated by solution processing of hybrid inks based on Ti₃ C₂ T_x MXene and ultralong MnO₂ nanowires. The resulting Ti₃ C₂ T_x /MnO₂ NWs hybrid paper manifests a remarkable areal capacitance of up to 205 mF cm^-2 and outstanding volumetric capacitance of 1025 F cm^-3 . Both the values are highly comparable with, or in most cases much higher than those of previously reported MXene-based flexible electrodes. The excellent energy storage performance is well maintained with a capacitance retention of 98.38% during 10 000 charge-discharge cycles. In addition, the flexible supercapacitor demonstrates excellent flexibility and electrochemical stability during repeated mechanical bendings of up to 120°, suggesting great potentials for the applications in future flexible and portable electronics.