Hierarchical Carbon Materials Research Articles

Biomass valorization of Mangifera Indica into hierarchical carbon materials with self-doping oxygen assisted carbonization for supercapacitor applications

ABSTRACT The exploration of biocompatible energy storage media for future generations has been continuously carried out. This includes the investigations of electrode materials that are renewable, environmentally friendly, cost-effective, and rich in heteroatoms. The electrode materials undergo carbonization as a promising thermochemical process to create an active material with a porous structure of well-defined and controlled geometry. The main objective of this study is to thoroughly examine the conversion process of electrode materials derived from Mangifera Indica Seed Shells (MIS) using carbonization and activation methods for supercapacitor applications. Pyrolysis at various temperatures was carried out to determine the definitive influence of carbonization temperature on the capacitive performance of MIS active materials. The optimum carbonization temperature of 600°C significantly enhances mesoporosity, which is positively correlated to the specific surface area, hierarchical structure, and the presence of self-doping oxygen, leading to a substantial increase in capacitive behavior. In the experiment, the MIS samples were used as electrodes for supercapacitor cells, and they were found to exhibit a specific capacitance of 255 Fg−1. The goal of this study is to offer a sustainable solution by using biomass as an active material for high-performance supercapacitor cells that can be utilized in energy storage applications.

Exploring the Potential of Hierarchical Zeolite-Templated Carbon Materials for High-Performance Li-O2 Batteries: Insights from Molecular Simulations.

The commercialization of ultrahigh capacity lithium-oxygen (Li-O2) batteries is highly dependent on the cathode architecture, and a better understanding of its role in species transport and solid discharge product (i.e., Li2O2) formation is critical to improving the discharge capacity. Tailoring the pore size distribution in the cathode structure can enhance the ion mobility and increase the number of reaction sites to improve the formation of solid Li2O2. In this work, the potential of hierarchical zeolite-templated carbon (ZTC) structures as novel electrodes for Li-O2 batteries was investigated by using reactive force field molecular dynamics simulation (reaxFF-MD). Initially, 47 microporous zeolite-templated carbon morphologies were screened based on microporosity and specific area. Among them, four structures (i.e., RHO-, BEA-, MFI-, and FAU-ZTCs) were selected for further investigation including hierarchical features in their structures. Discharge product cluster analysis, self-diffusivities, and density number profiles of Li+, O2, and dimethyl sulfoxide (DMSO) electrolyte were obtained to find that the RHO-type ZTC exhibited enhanced mass transfer compared to conventional microporous ZTC (approximately 31% for O2, 44% for Li+, and 91% for DMSO) electrodes. This is due to the promoted formation of small-sized product clusters, creating more accessible sites for oxygen reduction reaction and mass transport. These findings indicate how hierarchical ZTC electrodes with micro- and mesopores can enhance the discharge performance of aprotic Li-O2 batteries, providing molecular insights into the underlying phenomena.

Cobalt Phthalocyanine-Doped Polymer-Based Electrocatalyst for Rechargeable Zinc-Air Batteries.

Rechargeable zinc-air batteries (RZAB) have gained significant attention as potential energy storage devices due to their high energy density, cost-effectiveness, and to the fact that they are environmentally safe. However, the practical implementation of RZABs has been impeded by challenges such as sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), including poor cyclability. Herein, we report the preparation of cobalt- and nitrogen-doped porous carbon derived from phloroglucinol-formaldehyde polymer networks with 2-methyl imidazole and cobalt phthalocyanine as precursors for nitrogen and cobalt. The CoN-PC-2 catalyst prepared in this study exhibits commendable electrocatalytic activity for both ORR and OER, evidenced by a half-wave potential of 0.81 V and Ej=10 of 1.70 V. Moreover, the catalyst demonstrates outstanding performance in zinc-air batteries, achieving a peak power density of 158 mW cm-2 and displaying excellent stability during charge-discharge cycles. The findings from this study aim to provide valuable insights and guidelines for further research and the development of hierarchical micro-mesoporous carbon materials from polymer networks, facilitating their potential commercialisation and widespread deployment in energy storage applications.

A portable electrochemical immunosensor for ovarian cancer uses hierarchical microporous carbon material from waste coffee grounds.

A simple label-free electrochemical immunosensor for ovarian cancer (OC) detection was developed using a hierarchical microporous carbon material fabricated from waste coffee grounds (WCG). The analysis method exploited near-field communication (NFC) and a smartphone-based potentiostat. Waste coffee grounds were pyrolyzed with potassium hydroxide and used to modify a screen-printed electrode. The modified screen-printed electrode was decorated with gold nanoparticles (AuNPs) to capture a specific antibody. The modification and immobilization processes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The sensor had an effective dynamic range of 0.5 to 50.0 U mL-1 of cancer antigen 125 (CA125) tumor marker with a correlation coefficient of 0.9995. The limit of detection (LOD) was 0.4 U mL-1. A comparison of the results obtained from human serum analysis with the proposed immunosensor and the results obtained from the clinical method confirmed the accuracy and precision of the proposed immunosensor.

Facile template-free synthesis of 3D cluster-like nitrogen-doped mesoporous carbon as metal-free catalyst for selective oxidation of H2S

Construction of metal-free carbon-based materials for efficient sulfur resource recovery in pollutant H2S is very critical for both applied environmental catalysis and fundamental material exploration. Herein, we report a template-free hydrothermal method to prepare hierarchical nitrogen-doped mesoporous carbon (HNMCs) materials with abundant nitrogen sites and large BET surface area. The representative HNMC-800 achieves a H2S conversion of ∼100% and sulfur selectivity of ∼95% at 150 °C in H2S selective oxidation. Moreover, HNMCs catalysts are resistant to sulfur poisoning, displaying good catalytic durability, with no significant loss of sulfur yield in the run of 80 h, outperforming the pure active carbon, g-C3N4, and commercial Fe2O3. This work provides the possibility of utilizing hierarchical nitrogen-doped carbon materials as metal-free catalysts for the selective oxidation of H2S.

A candy-like photocatalyst by wrapping Co, N-co-doped hollow carbon sphere with ultrathin mesoporous carbon nitride for boosted photocatalytic hydrogen evolution

Hierarchical carbon material is used as a star cocatalyst in the field of photocatalysis due to its excellent catalytic properties. In this work, mesoporous carbon nitride sheet (MCNS) photocatalyst introduced nitrogen-doped hollow carbon spheres assembled with cobalt nanoparticles (Co@NHC) is synthesized by electrostatic adsorption. A series of characterizations are analyzed to display the structures, morphologies and optical properties of as-prepared materials. The photocatalytic activity of Co@NHC/MCNS material is evaluated with hydrogen evolution under visible light irradiation. The results indicate that 5 wt% Co@NHC/MCNS material reveals higher photocatalytic activity of hydrogen evolution rate of 3675 µmol/g with 4 h reaction time, which is 159 times than that of pure MCNS material. The carbon material with excellent charge transport properties can effectively accelerate the charge transfer from ultrathin MCNS to cobalt nanoparticles. The goal of improving the photocatalytic performance of Co@NHC/MCNS material is achieved. As a result, it provides a feasible and promised approach for doping transition metals to enhance photocatalytic activity.

Accurately control the micropore/mesopore ratio to construct a new hierarchical porous carbon with ultrahigh capacitance and rate performance

The synthesis of porous carbon materials with high surface area is an important method to improving their specific capacitances. However, the misfitting distribution of micropore/mesopore leads to serious recession under high current densities. Herein, we report a set of combination methods to accurately control the micropore/mesopore ratio to achieve a hierarchical carbon material with ultra-large capacitance and extra-high rate performance. These methods include adjusting Al/Zn ratios, decarboxylation, zinc volatilization, removal of nano-Al2O3, and KOH–KCl activation. The first four contribute to micropore structure creation to increase the specific capacitance at low current, while the last one contributes to mesoporous structure formation to increase the specific capacitance at high current. It is found that the corrosion of the excess micropores to form new mesopores and transparent graphene greatly enhances ion diffusion kinetic process and rate performance. Based on these findings, the optimized MDAPC provides a superior specific capacitance of 433 F g−1 at 1 A g−1, 324 F g−1 at 200 A g−1, and 217 F g−1 at 750 A g−1, indicating its ultra-large specific capacitance and extra-high rate performance. These findings provide a research foundation for the future development of hierarchical porous carbon materials with outstanding capacitance, rate performance and durability.

In-situ nitrogen and Cr2O3 co-doped MOF-derived porous carbon supported palladium nanoparticles: A highly effective catalyst towards formic acid dehydrogenation

Fast and high selective dehydrogenation of formic acid (FA) is regarded as one of the most promising pathways to obtain the clean energy carrier: hydrogen. In this work, a nitrogen and Cr2O3 co-doped hierarchical carbon material has been successfully synthesized by in-situ pyrolysis of NH2-MIL-101(Cr) in one step, followed by boiling in hot NaOH solution for surface etching. The activated carbon material is used to anchor the ultrafine Pd nanoparticles (2.18 nm) for formic acid dehydrogenation (FAD). As a result, the 5 wt% Pd@Cr2O3-NPCB-850 exhibits an excellent catalytic activity towards FAD: the turnover frequency (TOF) value is as high as 11 241 h−1 at 333 K, and the selectivity of H2 is up to 100%. The excellent catalytic performance is mainly attributed to the existence of N species and Cr2O3, which plays an important role of electron transfer and anti-aggregation. Our studies open a new methodology for convenient and fast syntheses of nitrogen and metal oxide co-doped activated carbon material, which also provides potential access for producing more highly effective catalysts for other catalytic reactions.

Biomass-Derived Carbon Materials: Controllable Preparation and Versatile Applications.

Biomass-derived carbon materials (BCMs) are encountering the most flourishing moment because of their versatile properties and wide potential applications. Numerous BCMs, including 0D carbon spheres and dots, 1D carbon fibers and tubes, 2D carbon sheets, 3D carbon aerogel, and hierarchical carbon materials have been prepared. At the same time, their structure-property relationship and applications have been widely studied. This paper aims to present a review on the recent advances in the controllable preparation and potential applications of BCMs, providing a reference for future work. First, the chemical compositions of typical biomass and their thermal degradation mechanisms are presented. Then, the typical preparation methods of BCMs are summarized and the relevant structural management rules are discussed. Besides, the strategies for improving the structural diversity of BCMs are also presented and discussed. Furthermore, the applications of BCMs in energy, sensing, environment, and other areas are reviewed. Finally, the remaining challenges and opportunities in the field of BCMs are discussed.

CO2-Derived Hierarchical Porous Carbon Electrode and Interlayer Doped with Nitrogen for Lithium-Sulfur Battery

Shuttle phenomena of lithium polysulfides (LiPSs) in lithium sulfur (Li-S) batteries is a serious obstacle to commercialization of Li-S battery. Various studies are being conducted to mitigate the shuttle effect, but among them, the approach using an interlayer has been introduced. This study proposes a hierarchical carbon material for both carbon cathode composite and interlayer synthesized from gaseous carbon dioxide. The highly porous carbon material used as a cathode enables a homogeneous distribution of active materials such as sulfur without agglomeration and allows rapid diffusion of ions. In addition, the interlayer made in this study is 30wt% lighter than the existing fiber-type paper layer based on its high porosity and at the same time has a very high 15.5% nitrogen atoms. Excess N atoms including pyridinic-N and pyrrolic-N contained in the interlayer prevent diffusion of LiPSs to the counter electrode through strong chemical bonds with LiPSs, and also greatly improve conductivity, minimizing resistance related to charge transfer. As a result, the cells assembled with them maintain a capacity of 700 mAh g−1 after 500 cycles at 0.5 C. In addition, it can exhibit a capacity of 697 mAh g−1 even at a high current density of 7.0 C.

Bimetallic AgNi nanoparticles anchored onto MOF-derived nitrogen-doped carbon nanostrips for efficient hydrogen evolution

Hydrogen energy has long been recognized as a clean alternative to conventional fossil fuels, which can be applied in a wide range of transportation and power generation applications. The rational design and engineering of high-performance and robust catalysts for hydrogen evolution reaction (HER) shows not a great significance but a challenge for efficient electrochemical water splitting. Herein, a new type of Ni-based Ni-ABDC precursor has been obtained, which leads to the formation of N-doped porous carbon nanomaterials uniformly coated with well-proportioned bimetallic AgNi alloys via a stepwise strategy. To their credit, all samples of AgNi/NC-X are structurally calcined from the pristine AgNi-ABDC-X by tuning the different concentration of AgNO3, which means all of them maintain the vermicelli-like morphology compared with Ni-ABDC. The series of AgNi/NC-X materials can be regarded as effective electrocatalysts for HER both in acidic and alkaline media, but an acid-leaching phenomenon is observed. Among them, the as-prepared AgNi/NC-2 exhibits a low overpotential of 103 mV at the current density of 10 mA cm−2 and decent durability with a high retention rate of 90.9% after 10 h in 1.0 mol L−1 KOH electrolyte. The compelling HER properties of AgNi/NC-2 can be attributed to the synergistic effect between the hierarchical carbon materials, partial N-doping and abundant AgNi alloys. Meanwhile, this study provides a practicable method for the development of efficient HER electrocatalysts for energy applications, which can be conveniently prepared through the reasonable introduction of active components in the crystalline inorganic-organic precursors.

Revealing Molecular Mechanisms in Hierarchical Nanoporous Carbon via Nuclear Magnetic Resonance

Author(s): Mao, H; Tang, J; Xu, J; Peng, Y; Chen, J; Wu, B; Jiang, Y; Hou, K; Chen, S; Wang, J; Lee, HR; Halat, DM; Zhang, B; Chen, W; Plantz, AZ; Lu, Z; Cui, Y; Reimer, JA | Abstract: Hierarchical nanoporous carbons combining pore sizes of different length scales are highly important for separation processes. However, critical questions remain regarding the hierarchical structure regulation and the molecular mechanisms of gaseous adsorbate uptake and interactions within the hierarchical nanoporous carbons. These materials present characterization challenges in that there are no experimental techniques that can elucidate the molecular mechanisms of the organic compounds and CO within the materials. We deployed multidimensional solid-state nuclear magnetic resonance (NMR) to generate maps of guest-framework interactions as a function of adsorbate concentrations and adsorption times. The NMR spectra provide insight toward the design of effective hierarchical pore structures. Our materials show a high volatile organic compounds/CO physisorption capacity, which reveals promising application to carbon-capture strategies to mitigate global warming. 2 2

Heterogeneous Interface Induced the Formation of Hierarchically Hollow Carbon Microcubes against Electromagnetic Pollution.

Carbon materials with multilevel structural features are showing great potentials in electromagnetic (EM) pollution precaution. With ZIF-67 microcubes as a self-sacrificing precursor, hierarchical carbon microcubes with micro/mesoporous shells and hollow cavities have been successfully fabricated with the assistance of rigid SiO2 coating layers. It is found that the SiO2 layer can effectively counteract the inward shrinkage of organic frameworks during high-temperature pyrolysis due to intensive interfacial interaction. The obtained hollow porous carbon microcubes (HPCMCs) exhibit larger Brunauer-Emmett-Teller surface area and pore volume than porous carbon microcubes (PCMCs) directly derived from ZIF-67 microcubes. The unique microstructure is confirmed to be favorable for conductive loss and interfacial polarization, thus boosting the overall dielectric loss capability of carbon materials. Besides, hollow cavity will also promote multiple reflection of incident EM waves and intensify the dissipation of EM energy. As expected, HPCMCs harvest better microwave absorption performance, including strong reflection loss intensity and broad response bandwidth, than many traditional microporous/mesoporous carbon materials. This study provides a new strategy for the construction of hierarchical carbon materials and may inspire the design of carbon-based composites with excellent EM functions.

Hierarchical, seamless, edge-rich nanocarbon hybrid foams for highly efficient electromagnetic-interference shielding

Lightweight, flexible, ultrahigh-performance electromagnetic-interference (EMI) shielding materials are urgently required in the areas of aircraft/aerospace, portable and wearable electronics. Herein, 1D carbon nanotubes (CNT) and carbon nanofibers (CNF) with 2D edge-rich graphene (ERG) are used to form a lightweight, flexible CNT-ERG-CNF hybrid foam. This foam was fabricated through a self-sacrificial templating chemical vapor deposition process, where nanocarbons bond through covalent bonding, forming a hierarchical 3D hybridized carbon nanostructure. Multistage conductive networks and heterogeneous interfaces were constructed using edge-rich nanocarbons to increase the induced currents and interfacial polarization which makes great contributions to achieve high absorption electromagnetic shielding effectiveness (SEA). The CNT-ERG-CNF hybrid foam exhibits EMI shielding effectiveness (SE) exceeding 55.4 dB in the X-band while the specific SE (SSE, SE divided by mass density) achieves 9200 dB cm3 g-1, which surpasses that of nearly all other carbon-based composite materials. Furthermore, the structural stability and durability of the flexible CNT-ERG-CNF hybrid foams is examined by measuring EMI SE after 10000 times cyclic bending. Remarkably, this work not only provides a new idea for preparing hierarchical carbon materials for a wide range of applications, but presents some fundamental insights for achieving higher absorption losses in EMI shielding materials.

Three-Dimensional Ordered Porous Carbon for Energy Conversion and Storage Applications

The performance of energy storage devices is highly related to the properties of electrode materials, such as components, morphology, configurations and so on. As a typical hierarchical carbon material, three-dimensional ordered porous carbon (3D-OPC) has unique characteristics of low cost, large specific surface area, highly ordered channels, and high electronic and ionic conductivity, which shows great potential in energy storage and conversion applications. In this minireview, we summarize various template-assisted preparation methods for 3D-OPC, including hard-, ice- and self-templated approaches, and their applications in electrocatalysis, batteries and supercapacitors. Additionally, the critical roles of vertical channels in 3D-OPC when used as electrodes are also discussed. Finally, the current challenges and future research outlook of 3D-OPC are proposed.

Molten salt synthesis of hierarchically porous carbon for the efficient adsorptive removal of sodium diclofenac from aqueous effluents

Pharmaceutical and personal care products (PPCPs) are emerging organic pollutants (EOPs) that pose a serious peril to both aquatic biota and mankind's health. The development of novel adsorbent materials for the effectual treatment of PPCPs-included wastewater has become one of the foremost research issues in the environmental research area. In this work, a hierarchical carbon material (GHPC), produced through the simple and effective molten salt route adopting glucose and the eutectic mixture (KCl/ZnCl2) as the carbon precursor and the pore generator, respectively, was applied in adsorption of sodium diclofenac, as a representative of organic contaminants of emerging concern, from aqueous solution. GHPC manifested superior adsorption performance towards DFC, which was believed to stem from its high surface area and total pore volume, hierarchically porous texture, and the presence of plentiful available functional groups. Langmuir adsorption isotherm, and the pseudo-second-order kinetics were found to be appropriate to represent the adsorption equilibrium and kinetics, respectively. Hydrogen bonding interaction was thought to be the main mechanism underlying DFC (as H-bond donor) adsorption onto GHPC (as H-bond acceptor). The impacts of the co-existing cations and anions on the adsorptive removal of DFC were additionally scrutinized. Finally, GHPC demonstrated good reusability properties that qualify it for the practical remediation of PPCPs-included wastewater.

Hierarchical meso- and macroporous carbon from lignin for kraft lignin decomposition to aromatic monomers

In this study, lignosulfonate is converted to hierarchical carbon materials via templating methods, which are used as supports of molybdenum carbide catalysts for Kraft lignin decomposition to aromatic monomers. The results show that hierarchical carbon materials with micropores, mesopores of about 8 nm, and macropores of about 400 nm are obtained from calcium and sodium lignosulfonates using coupled SiO2+F127 templates with high ash-free carbon yields of about 50 %. The F127 template tends to assemble on SiO2 surface along with radial direction to form ordered meso-/macroporous structure of the carbon materials. The β-Mo2C supported on the hierarchical carbon material exhibits high catalytic performance with aromatic yield of 0.586 g/g Kraft lignin, and the BTX (benzene, toluene, and xylene) components and BTX-derived alcohols donate 21 % and 32 % of the aromatics, respectively. The mesopores benefit the accessibility of lignin fragments to active sites and interconnection between macropores, and the macropores enhance the impregnation of highly-dispersed nano β-Mo2C particles into pore structures. The hierarchical carbon materials from pulping waste lignin shows potential for macromolecular lignin decomposition.

Hierarchical polypyrrole/graphene/melamine composite foam for highly compressible all-solid-state supercapacitors

Nanostructured carbon materials have shown promising applications for energy storage because of their high capacitive characteristic. However, developing three-dimensional (3D) hierarchical carbon materials with both high compressibility and capacitance is still challenging. Herein, we report the fabrication of hierarchical polypyrrole (PPy)/graphene (reduced graphene oxide (G) and holey reduced graphene oxide (h-G))/melamine composite foam through a simple template method. By systematically optimizing the mass ratios of the G/h-G and the sizes of the PPy nanoparticles (PPy NPs), the as-prepared composite electrode displays a gravimetric capacitance of 422.6 F g−1 at a current density of 0.5 A g−1. Due to the interconnected h-G/G network and elastic melamine foam (MF) skeleton, the as-prepared composite electrode also shows compressible performance, which can be compressed to a strain of 60% and completely recover to its original shape when released. When the composite electrodes are assembled to a compressible supercapacitor which shows a stable capacitance under different compressive strains (0%, 25%, 50% and 75%) and a long-term compression test at 50% strain for 100 cycles. Therefore, the successful preparation of compressible composite electrode should open many opportunities in compressible and durable energy storage devices.

Electrodeposition of Metal Oxides on Spray-Coated Nanostructured Carbon Framework As High Performance Electrode Materials for Asymmetric Pseudocapacitors

Combining transition metal oxides and nanostructured hierarchical carbon materials is considered as one of the best strategy to achieve high performance supercapacitors electrodes [1]. Here is reported a novel way to increase energy densities while maintaining high power densities exploiting pseudocapacitance and nanostructuration of electrode materials.In the first part of this study, carbon nanotubes/graphene/manganese dioxide nanostructured films were designed as pseudocapacitors electrodes (Fig. A). While MnO2 is a well-known pseudocapacitive cathode material and will increase energy densities [2], nanostructured carbon materials provide high electronic conductivity and specific surface. The challenge is to assemble these three materials (CNTs/G/MnO2) into a nanostructured electrode with controlled homogeneity, morphology, and composition. First, carbon nanotubes and graphene foils are associated in a specific multi-layered organization onto a current collector by dynamic spray gun deposition. It creates a controlled porous network in the electrodes. This deposition method used for nanostructuration of thin films generates homogeneous mats with tunable thickness. This structuration of the carbon nanomaterials is reproducible, easily scalable and low-cost considering that it is compatible with large surfaces. The CNTs/G multilayered structure provides a good accessibility with an appropriate porosity for ion insertion (pores of 2 to 6 nm), a high specific surface area (~360 m2/g), and an electrically conductive network (~3600 S/m), all necessary to confer high power densities. Our approach consists in synthesizing MnO2 by anodic electrodeposition directly onto the conductive nanostructured carbon framework. Electrodeposition is very versatile [3] and simply. The morphology of the manganese dioxide (shape, particles size, and mass loading) can be controlled and the electrochemical performances can be tuned by adjusting the deposition conditions. The MnO2 nanoparticles are deposited through the thickness (seen in cross section Figure A) of the carbon mat with controlled sizes ranging from 50 to 200 nm.Materials are characterized by SEM, XPS, microporosity analysis and electrochemistry. Results demonstrate that the capacitance can reach up to 220 F/g for binder free electrodes with a MnO2 mass loading of 55%. The pseudocapacitive oxide insures a faradaic contribution that enhances the specific capacitance by a factor 5 compared to the carbon nanomaterials structure only. The electrodes present an outstanding stability of 96% over 3 000 cycles in aqueous electrolytes (Na2SO4 1M). Then an asymmetric system with activated carbon as the negative electrode is developed to demonstrate the energy density increase compared to a symmetric system with activated carbon as electrodes. When adding MnO2 to the cathode the exploitable potential window can be widen up to 1.4V and the energy density increases from 1 Wh/kg to 6 Wh/kg for a power density of 0.7 kW/kg. Stability of 85% in capacitance was demonstrated for 20 000 cycles on this system.The second part of the contribution is devoted to molybdenum oxide (MoO3) that has been recently introduced as an appropriate anode material for pseudocapacitors in view of its low cost nature and high electrochemical activity [4,5]. It has been reported to be suitable in terms of potential window as a negative counterpart to manganese oxide in asymmetric pseudocapacitors [6]. This study focuses on the development of a carbon nanotubes/molybdenum oxide composite by spray-coating and cathodic electrodeposition (Fig. B). The growth of this specific metal oxide is quite complex with several possible intermediaries presenting different oxidation states depending on the environment [7]. Studies on the impact of the chemical and electrochemical conditions on the morphology, crystallinity, and homogeneity of the oxide layer are performed and thermal treatments aiming to enhance these parameters and stabilize the electrochemical performances are explored. Solubility of the deposited MoOx has been found to be a major issue in aqueous electrolytes and in that regard tests have been performed in organic electrolytes with lithium salts to insure stability of the final system. First results obtained for a simple binary MoOx-CNTs electrode already present a good maximum specific capacitance of 110 F/g. [1] National Science Review, 4, 1 (2017) 71–90 [2] Prog. Mater. Sci. 74 (2015) 51-124. [3] Ceram. Int. 44 (2018) 10863-10870. [4] Chem. Commun., 2011, 47, 10058–10060 5] Materials Letters 66 (2012) 102–105 [6] Adv. Funct. Mater. 2013, 23, 5074–5083 [7] Analytica Chimica Acta 496 (2003) 39–51 Figure 1

Membrane and electrode engineering of high-performance lithium-sulfur batteries modified by stereotaxically-constructed graphene

Lithium-sulfur batteries have great potential as the next-generation clean energy storage systems due to their remarkable high-energy density and electrochemical capacity. Additionally, sulfur is used as a cathode material because of its characteristics of a low cost, environmental friendliness, and abundant nature. However, the polysulfide shuttle effect decreases the electrochemical performance of lithium-sulfur batteries. Here, a rational membrane/electrode design has been applied to lithium-sulfur batteries. A three-dimensional hierarchical nanoporous carbon material derived from cationic resins in a cost-effective process was synthesized at a high temperature and utilized as an intermediate layer to improve the rate capability and cycle stability of lithium-sulfur batteries. Furthermore, stereotaxically -constructed multiporous graphene with a high conductivity (1.6 × 10 3 S m −1 ), porosity and large specific surface area (824 m 2 g −1 ) has been applied in the cathode to increase the conductivity of sulfur, improve the transport of lithium-ions and increase the contact with the electrolyte. In particular, stereotaxically-constructed multiporous graphene was used as the sulfur carrier (sulfur loading 70 wt %). The electrochemical results revealed an initial discharge capacity of the hierarchical nanoporous carbon material intermediate layer-coated membrane of 1008 mAh g −1 at 0.5C, and the reversible capacity was 532 mAh g −1 at 1C after 300 cycles. Based on the experimental evidence and analyses, we concluded that the enhanced performance is due to the confinement of lithium polysulfides by the micropores and mesoporous structure of the hierarchical porous carbon material and the increased transportation of lithium ions and the improved wettability of membrane by electrolyte. • Hierarchical nanoporous carbon material (HNCM) has been synthesized at a high temperature by a cost-effective process. • The HNCM reduce the interfacial resistance and increase the wettability of membrane by electrolyte. • The stereotaxically-constructed multiporous graphene (SCMG) employed as sulfur host for Li–S batteries. • The resultant lithium-sulfur batteries exhibit a superior rate capacity and improved cycling capacity. • The multiple physical sorption of the modified layer greatly inhibit the shuttling of polysulfide.