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The development of inexpensive and efficient Pt-free electrocatalysts for the hydrogen evolution reaction (HER) is greatly crucial for water electrolysis. Tungsten carbide (WC) exhibiting a Pt-like electronic structure represents an attractive alternative, although its overall performance is limited by the strong W-H bond that impedes hydrogen desorption. Here, we employed an in-situ interface engineering strategy to construct high-performance and cost effective electrocatalysts comprising WC/tungsten phosphide (WP) heterostructures that were anchored on N,P-codoped carbon (WC/WP@NPC) via a one-step pyrolysis of a melamine polyphosphate/WO3 hybrid in an inert atmosphere. Owing to the crystal structure compatibility and electron-rich property of WP, it optimizes the electronic structure and hydrogen adsorption configuration of WC, thus significantly weakening the W-H bond with a thermoneutral Gibbs free energy of hydrogen adsorption (ΔGH*) of −0.05 eV. Additionally, NPC ensures fast electron transport and structural stability of the WC/WP@NPC ternary architecture. These synergistically lead to outstanding HER performances of the catalyst in acidic and alkaline media. Our finding offers a new strategy for designing Pt-alternative electrocatalysts with outstanding electrochemical performances for high-efficiency water splitting and other applications.

MoS2 has attracted much interest for the potential application in sodium-ion batteries (SIBs) anodes because of the high theoretical capacity and electrochemical activity with Na. However, poor electrochemical performance caused by severe volume variations during the charge/discharge processes limits its practical application. Herein, we present an elaborately designed architecture comprising ultrafine MoS2 nanoparticles covalently bonded to N, S co-doped carbon (MoS2/NSC) via an in situ solid-state growth process, which displays high-capacity Na storage, fast sodiation/desodiation kinetics, and substantially mitigated volume fluctuations. As a consequence, MoS2/NSC delivers outstanding Na storage performances including a high reversible capacity of 340 mA h g−1 at 100 mA g−1 and a rate capacity of 208 mA h g−1 at 2000 mA g−1. Further assembling with a Na3V2(PO4)3/C cathode, the full-cell delivers a specific capacity of 238 mA h g−1 after 80 cycles at 50 mA g−1, demonstrating the great potential of our MoS2/NSC electrode. Density function theory calculations manifest that NSC not only presents strong binding to MoS2 but also significantly decreases the Na ion diffusion energy barrier, thus leading to robust structure stability and fast electrode kinetics. This study may open a new and efficient avenue for developing advanced MoS2 anodes for SIBs.

Potassium-ion batteries (PIBs) are attracting increasing attention due to the abundance of K resources, but the sluggish kinetics and inferior cycling stability of anodes still hinder their application. Herein, we present a hybrid 1T/2H phase MoSe2 anode, which shows noticeable pseudocapacitive response and fast kinetics for K storage. Correspondingly, superior electrochemical performances including a high reversible capacity of 440 mA h g-1 after 100 cycles at 0.1 A g-1 and superb rate capacity of 211 mA h g-1 at 20.0 A g-1 are achieved. We believe this work may shed light on the phase engineering of transition metal compounds for rapid charging PIBs.

Electrocatalysts are considered the most promising candidates in ameliorating the slow kinetics of Li-S batteries (LSBs), however, the issue of insufficient catalytic capability remains to be addressed. Herein, we report an integrated catalytic network comprising graphitic carbon-encapsulated/bridged ultrafine NiCoP embedded in N, P-codoped carbon (GC-uNiCoP@NPC) as a highly competent catalyst for sulfur-based species conversions. By profiling the evolution map of Li-S chemistry via operando kinetic analyses, GC-uNiCoP@NPC is demonstrated to possess versatile yet efficient catalytic activity for sulfur reduction/evolution reactions, especially the rate-determining heterogeneous phase transitions. As a result, GC-uNiCoP@NPC enables high capacity and stable cycling of sulfur cathode under high areal loading and lean electrolyte. Moreover, pouch cells assembled under practical conditions present promising performance with a specific energy of 302 Wh kg

Thanks to their light-weight, wearing comfort, and amenability to be woven into textiles, solid-state fiber supercapacitors (FSCs) have been considered as promising energy storage devices for wearable electronics. Carbon fibers (CFs) have the merits of both superior mechanical strength and conductivity, excellent flexibility, doped by heteroatoms, good knittability/weavability, and most importantly have already been produced in ton-scale in form of continuous tows; however, their applications in FSCs are limited to current collectors or conductive scaffolds as a result of the inert surface composed of highly compacted and well-aligned graphitic sheath. Inspired by Cattail’s unique compact core-fluffy sheath structure, herein, we develop an electrochemical method to directly transform CFs into high performance electrode by controllably swelling the well-aligned graphitic sheath without disturbing the core fiber of interlinked randomly-orientated carbon nanocrystals. Compared to pristine CFs, the obtained fiber electrode delivers more than two-order improved capacitance (87.2 F cm−3 at 1.0 A cm−3) with excellent rate capability and cycling stability, enabling the as-fabricated solid-state supercapacitor much enhanced energy density. The scalability of our method is demonstrated, which is believed to be compatible with the state-of-art commercial processing techniques, thus holds great promise for future development of electronic-textiles.

A versatile low-temperature molten salt approach has been developed for fabricating a MoS2@CoS2 heterostructure electrocatalyst, where low-cost molten KSCN serves as both the reaction medium and sulfur source. The as-obtained electrocatalyst with a defect-rich structure is highly efficient for the hydrogen evolution reaction (HER), delivering a low overpotential of 96 mV at an HER current density of 10 mA cm-2, a small Tafel slope of 60 mV dec-1, and outstanding durability. Density functional theory (DFT) calculations suggest that the heterostructures present an optimized Gibbs free energy of hydrogen adsorption (ΔGH*) close to zero, which is responsible for the excellent HER performance.

Despite red phosphorous (P)-based anodes hold great promise for advanced lithium-ion batteries due to their high theoretical capacity, their practical application is hindered by poor electronic conductivity and drastic volume changes during charge-discharge processes. In order to tackle these issues, herein, a facile grinding method was developed to embed sub-micro- and nano-sized red P particles in N,P-co-doped hierarchical porous carbon (NPHPC). Such a unique structure enables P@NPHPC long-cyclic stability (1120 mA h g−1 after 100 cycles at 100 mA g−1) and superior rate performance (248 mA h g−1 at 6400 mA g−1). It is believed that our method holds great potential in scalable synthesis of P@carbon composites for future practical applications.

Heteroatom-doped carbon nanostructures with uniform size and morphology, well-designed architectures, and minimized interfacial resistance have been recognized as promising electrode materials for energy storage, but remain a crucial challenge. Herein, we develop a general approach of polarity-induced decoration of a monolayer sheath of metal-organic framework (MOF) particles with excellent uniformity in size and morphology on electrospun polymer nanofibers. These hybrid nanofibers are facilely converted into nitrogen-doped nanofibrous carbon (denoted as N-NFC) during pyrolysis. The thus-obtained N-NFC features (1) a one-dimensional nanofibrous structure with a highly conductive core, (2) a monolayer sheath of hollow carbon-frames with uniform size and morphology, (3) plenty of micro/mesopores with a highly accessible surface area, and (4) a high N-doping level, all of which guarantee its good electrochemical performance with a high capacitance of 387.3 F g⁻¹ at 1 A g⁻¹. In a solid-state supercapacitor, it delivers excellent rate capability (78.0 F g⁻¹ at 0.2 A g⁻¹ and 64.0 F g⁻¹ at 1 A g⁻¹), an enhanced energy density of 7.9 W h kg⁻¹ at a power density of 219 W kg⁻¹, and outstanding cycling stability with 90% capacity retained over 10 000 cycles at 1 A g⁻¹. This work was supported by the National Natural Science Foundation of China (61704076), the Natural Science Foundation of Jiangsu Province (BK20171018), the NanjingTech Start-Up Grant (3983500150), and the Jiangsu Specially-Appointed Professor program (54935012).

Developing high-efficiency electrocatalysts for the hydrogen evolution and oxidation reactions (HER/HOR) in alkaline electrolytes is of critical importance for realizing renewable hydrogen technologies. Ruthenium phosphides (RuP

Potassium-ion batteries (PIBs) are attracting increasing attention due to the abundance of K resources, but the sluggish kinetics and inferior cycling stability of anodes still hinder their application. Herein, we present a hybrid 1T/2H phase MoSe

A low-temperature doping approach has been developed for fabricating nitrogen and sulfur co-doped few-layer graphene (NS-FLG) by annealing graphene oxide in KSCN molten salt at 175 °C. The as-prepared NS-FLG with a high doping level and unique few-layer structure delivers remarkable performance for sodium-ion batteries (SIBs) in terms of a high reversible capacity of 325.4 mA h g-1 at 0.5 A g-1, a superb rate capacity of 203.6 mA h g-1 at 10 A g-1, and ultra-long cyclability over 5100 cycles. This work provides a new avenue for exploring advanced graphene-based materials towards SIBs and even other electrochemical fields.

Li-chalcogen batteries, especially the Li-S batteries (LSBs), have received paramount interests as next generation energy storage techniques because of their high theoretical energy densities. However, the associated challenges need to be overcome prior to their commercialization. Elemental selenium, another chalcogen member, would be an attractive alternative to sulfur owing to its higher electronic conductivity, comparable capacity density, and moreover, excellent compatibility with carbonate electrolytes. Unlike LSBs, the research and development of Li-Se batteries (LSeBs) have garnered burgeoning attention but are still in their infant stage, where a comprehensive yet in-depth overview is highly imperative to guide future research. Herein, a critical review of LSeBs, in terms of the underlying mechanisms, cathode design, blocking layer engineering, and emerging solid-state electrolytes is provided. First, the electrolyte-dependent electrochemistry of LSeBs is discussed. Second, the advances in Se-based cathodes are comprehensively summarized, especially highlighting the state-of-the-art Sex Sy cathodes, and mainly focusing on their structures, compositions, and synthetic strategies. Third, the versatile separators/interlayers optimization and interface regulation are outlined, with a particular focus on the emerging solid-state electrolytes for advanced LSeBs. Last, the remaining challenges and research orientations in this booming field are proposed, which are expected to motivate more insightful works.

A versatile low-temperature molten salt approach has been developed for fabricating a MoS2@CoS2 heterostructure electrocatalyst, where low-cost molten KSCN serves as both the reaction medium and sulfur source. The as-obtained electrocatalyst with a defect-rich structure is highly efficient for the hydrogen evolution reaction (HER), delivering a low overpotential of 96 mV at an HER current density of 10 mA cm-2, a small Tafel slope of 60 mV dec-1, and outstanding durability. Density functional theory (DFT) calculations suggest that the heterostructures present an optimized Gibbs free energy of hydrogen adsorption (ΔGH*) close to zero, which is responsible for the excellent HER performance.

A facile and cost-effective method has been developed for the fabrication of Ni2P nanoparticles encapsulated in N,P-codoped carbon nanofibers (Ni2P@NPCNFs) using the commercialized products of melamine polyphosphate (MPP) and Ni foam. During the synthetic process, MPP serves as the solid phosphorus source for the phosphidation of Ni foam, and it simultaneously performs as a carbon source for the in situ growth of functionalized carbon nanofibers, resulting in a favorable architecture of an Ni2P well-integrated carbon matrix. With this unique structure, the resultant Ni2P@NPCNFs electrode shows remarkable Li-ion storage performance, in terms of high reversible capacity and long-cyclic lifespan (850 mAh g–1 at 200 mA g–1 after 450 cycles), as well as a good rate behavior (300 mAh g–1 at 3200 mA g–1). This work not only presents a new avenue to construct advanced Ni2P-based functional nanocomposites for Li-ion batteries but also paves the way to explore unique transition-metal phosphides toward diverse appli...

A hybrid structure consisting of boron-doped porous carbon spheres and graphene (BPCS-G) has been designed and synthesized toward solving the polysulfide-shuttle problem, which is the most critical issue of current Li-S batteries. The proposed hybrid structure showing high surface area (870 m2·g−1) and high B-dopant content (6.51 wt.%) simultaneously offers both physical confinement and chemical absorption of polysulfides. On one hand, the abundant-pore structure ensures high sulfur loading, facilitates fast charge transfer, and restrains polysulfide migration during cycling. On the other hand, our density functional theory calculations demonstrate that the B dopant is capable of chemically binding polysulfides. As a consequence of such dual polysulfide confinement, the BPCS-G/S cathode prepared with 70 wt.% sulfur loading presents a high reversible capacity of 1,174 mAh·g−1 at 0.02 C, a high rate capacity of 396 mAh·g−1 at 5 C, and good cyclability over 500 cycles with only 0.05% capacity decay per cycle. The present work provides an efficient and cost-effective platform for the scalable synthesis of high-performance carbon-based materials for advanced Li-S batteries.

For the first time, nitrogen and phosphorus codoped hierarchically porous carbon (NPHPC) has been explored as an efficient host for sulfur. The material is fabricated based on a scalable, one-step process involving the pyrolysis of melamine polyphosphate synthesized via a simple and versatile organic approach by using low cost industrial raw materials (melamine and polyphosphoric acid). The key features of NPHPC are the hierarchically porous structure and high surface area (1398 m 2 g −1 ) that not only benefit for maximum sulfur loading but also capable of suppressing the dissolution of polysulfides through physisorption. Meanwhile, the N and P codopants together with the thermally stable functionalities are favorable for binding polysulfides via chemisorption. Benefitting from the synergistic effect of structural confinement (physisorption) and chemical binding (chemisorption), the NPHPC/S composite with a high sulfur content of 73 wt% delivers high capacity (1580 mAh g −1 at 0.02 C) and long lifespan (200 cycles with 71% retention) for Li-S batteries. The present work highlights the importance of adopting heteroatom-doped hierarchically porous carbon for improving the performance of Li-S batteries, which may further stimulate more efforts in exploring advanced carbon-based hosts in the near future.

A general and mild strategy for fabricating defect-enriched graphene mesh (GM) and its application toward the anode of Li-ion batteries (LIBs) has been reported. The GM with a pore size of 60–200 nm is achieved by employing Fe2O3 as the etching reagent that is capable of locally etching the graphene basal plane in a relatively mild manner. Upon different drying technologies, that is, oven drying and freeze-drying, GMs with different porous structure are obtained. The electrochemical Li storage properties of GMs in comparison with graphene aerogels (GAs) disclose that both defect sites and porous structure are crucial for the final anodic performances. We show that only when merged with rich porosity, the GM anode can achieve a better Li storage performance than that of GA. Moreover, we further fabricated nitrogen-doped GM (NGM) using urea as the nitrogen source with a freeze-drying process. Benefiting from the unique structural characteristics, that is, plentiful defects, abundant pores, and nitrogen dopi...

Layered γ-type iron oxyhydroxide (γ-FeOOH) is a promising material for various applications; however, its sheet-shaped structure often suffers from instability that results in aggregation and leads to inferior performance. Herein, a kinetically controlled hydrolysis strategy is proposed for the scalable synthesis of γ-FeOOH nanosheets arrays (NAs) with enhanced structural stability on diverse substrates at ambient conditions. The underlying mechanisms for the growth of γ-FeOOH NAs associated with their structural evolution are systematically elucidated by alkalinity-controlled synthesis and time-dependent experiments. As a proof-of-concept application, γ-FeOOH NAs are developed as electrocatalysts for the oxygen evolution reaction (OER), where the sample grown on nickel foam (NF) exhibits superior performance of high catalytic current density, small Tafel slope, and exceptional durability, which is among the top level of FeOOH-based electrocatalysts. Density functional theory calculations suggest that γ-NiOOH in situ generated from the electrooxidation of NF would induce charge accumulation on the Fe sites of γ-FeOOH NAs, leading to enhanced OER intermediates adsorption for water splitting. This work affords a new technique to rationally design and synthesize γ-FeOOH NAs for various applications.

Tin (Sn)-based materials are potential alternatives to the commercial graphite anode for next generation Li-ion batteries, but their successful application is always impeded by fast capacity fading upon cycling that stemmed from huge volume variations during lithiation and delithiation. We develop an applicable strategy of encapsulating sub-10-nm-sized Sn-based nanoparticles (i.e., Sn and SnO2) in nitrogen/phosphorus codoped hierarchically porous carbon (NPHPC) or NPHPC-reduced graphene oxide hybrid (NPHPC-G) to effectively solve the issues of Sn-based anodes. Benefiting from the peculiar structure, the composites exhibit unprecedented electrochemical behaviors, for example, NPHPC-G@Sn and NPHPC-G@SnO2 deliver a high reversible capacity of ~1158 and ~1366 mAh g-1 at 200 mA g-1, respectively, and maintain at ~1099 mAh g-1 after 500 cycles and ~1117 mAh g-1 after 300 cycles. In situ transmission electron microscopy and ex situ scanning electron microscopy observations unveil that these composites are able to withstand the volume changes of Sn-based nanoparticles while sustaining the framework of the architectures and hence conferring outstanding electrochemical properties. Our present work provides both in situ and ex situ techniques for understanding the so-called synergistic effect between metals or metal oxides and carbons, which may offer rational guidance to design carbon-based functional materials for energy storage. MOE (Min. of Education, S’pore)

We have studied the quantum Fisher information of the XXZ spin chain model with Dzyaloshinskii–Moriya interaction, using the quantum renormalization-group method. The results show that the evolution behavior of quantum Fisher information with increasing lattice size can clearly illustrate the quantum transitions of this spin model. Moreover, it is demonstrated that the scaling property of quantum Fisher information at the critical point can be used to explain the spin correlation length of this model. The present work evidences the capability of the quantum Fisher information in characterizing quantum phase transitions in condensed matters.

The concept of quantum Fisher information (QFI) is used to characterize the localization transitions in three representative one-dimensional models. It is found that the localization transition in each model can be distinctively illustrated by the evolution of QFI. For the Aubry-Andre model, the QFI exhibits an inflexion at the boundary between the extended states and localized ones. In the t 1−t 2 model, the QFI has a transition point separating the extended states from the localized states, while the mobility edge of the QFI is energy dependent. Furthermore, nine energy bands in the Soukoulis-Economou (S-E) model can be clearly revealed by the QFI with global mobility edges and local mobility edges. The present work demonstrates the implication of the QFI as a general fingerprint to characterize the localization transitions.

Graphene fibers (GFs) are attractive materials for wearable electronics because of their lightness, superior flexibility, and electrical conductivity. However, the hydrophobic nature and highly stacked structure endow GFs similar characteristics in nature to solid carbon fibers. Therefore, the interior functionalization of GFs so as to achieve synergistic interaction between graphene nanosheets and active materials thus enhance the performance of hybrid fibers remains a challenge. Herein, a general metal-ion mediated strategy is developed to functionalize GFs and nanoparticles of Cu, Fe2O3, NiO, and CoO are successfully incorporated into GFs, respectively. As proof-of-concept applications, the obtained functionalized GFs are used as electrodes for electrochemical sensors and supercapacitors. The performances of thus-devised fiber sensor and supercapacitor are greatly improved.

The development of environment-friendly electrode materials is highly desired for the clean and sustainable Li-ion batteries (LIBs) system. Organic cathode materials that involve conducting polymers, organic carbonyl/sulfur compounds are expected to be promising candidates for future LIBs with a concept of “green and sustainable”. However, their battery performances are relatively worse than that of inorganic counterparts due to their low electronic conductivity and unwanted dissolution reactions occurring in electrolytes. Aimed to alter their performances, we herein focuses on the preparation of upgraded organic materials by chemical engineering of graphene oxide (GO) and the systematic study of their electrochemical performance as positive electrodes for LIBs. The obtained decarboxylated GO and carbonylated/hydroxylated GO electrodes show significantly enhanced electrochemical performance compared with that of the GO electrode. Our results demonstrate that the manipulation of oxygen functional groups on GO is an effective strategy to greatly improve the Li storage property of GO-based materials for advanced LIBs cathodes.

A simple and effective method for the preparation of amphiphilic graphene (AG) is presented under an organic solvent-free synthetic condition. The synthetic route first involves a cyclization reaction between carboxylic groups on graphene oxide and the amino groups on 5,6-diaminopyrazine-2,3-dicarbonitrile, and subsequent reduction by hydrazine. Results of UV-vis spectroscopy, Fourier transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Raman spectroscopy have confirmed that the covalent functionalization of graphene can be achieved through the formation of imidazo[4,5-b]pyrazine on the graphene sheets. As a result, AG can be successfully dispersed in water and common organic solvents. This work successfully provides a facile and efficient way to fabricate AG and may extend the potential applications of graphene-based materials in nanoelectronic devices, polymer fillers and biological field.

An easy and versatile method for the covalent functionalization of graphene oxide (GO) is reported. The functionalized GO is synthesized by a polyphosphoric acid-catalyzed cyclization reaction of the carboxylic groups on GO with the hydroxyl and amino groups on o-aminophenol and o-phenylenediamine, resulting in it being well dispersed in many organic solvents. The results may provide a way to extend the use of GO as a functional material in electronic devices and high performance structural materials.

The eg-orbital double-exchange mechanism as the core of physics of colossal magnetoresistance (CMR) manganites is well known, which usually covers up the role of super-exchange at the t2g-orbitals. The role of the double-exchange mechanism is maximized in La0.7Ca0.3MnO3, leading to the concurrent metal-insulator transition and ferromagnetic transition as well as CMR effect. In this work, by a set of synchronous Ru-substitution and Ca-substitution experiments on La0.7–yCa0.3+yMn1–yRuyO3, we demonstrate that the optimal ferromagnetism in La0.7Ca0.3MnO3 can be further enhanced. It is also found that the metal-insulator transition and magnetic transition can be separately modulated. By well-designed experimental schemes with which the Mn3+-Mn4+ double-exchange is damaged as weakly as possible, it is revealed that this ferromagnetism enhancement is attributed to the Mn-Ru t2g ferromagnetic super-exchange. The present work allows a platform on which the electro-transport and magnetism of rare-earth manganites can be controlled by means of the t2g-orbital physics of strongly correlated transition metal oxides.

N and S codoping of graphene is realized by a novel approach: covalent functionalization of graphene oxide using 2-aminothiophenol as a source of both N and S followed by thermal treatment. The resulting N- and S-codoped graphene has potential applications in high-performance lithium-ion batteries and as a metal-free catalyst for oxygen reduction reaction.

Hierarchically porous carbons are attracting tremendous attention in sustainable energy systems, such as lithium ion battery (LIB) and fuel cell, due to their excellent transport properties that arise from the high surface area and rich porosity. The state-of-the-art approaches for synthesizing hierarchically porous carbons normally require chemical- and/or template-assisted activation techniques, which is complicate, time consuming, and not feasible for large scale production. Here, a molecular-level design principle toward large-scale synthesis of nitrogen and phosphorus codoped hierarchically porous carbon (NPHPC) through an in situ self-activation process is proposed. The material is fabricated based on the direct pyrolysis of a well-designed polymer, melamine polyphosphate, which is capable of in situ self-activation to generate large specific surface area (1479 m2 g−1) and hierarchical pores in the final NPHPC. As an anode material for LIB, NPHPC delivers a high reversible capacity of 1073 mAh g−1 and an excellent cyclic stability for 300 cycles with negligible capacity decay. The peculiar structural properties and synergistic effect of N and P codopants also enable NPHPC a promising electrocatalyst for oxygen reduction reaction, a key cathodic reaction process of many energy conversion devices (for example, fuel cells and metal air batteries). Electrochemical measurements show NPHPC a comparable electrocatalytic performance to commercial Pt/C catalyst (onset potential of 0.88 V vs reversible hydrogen electrode in alkaline medium) with excellent stability (89.8% retention after 20 000 s continuous operation) and superior methanol tolerance.

We report a simple and efficient approach for fabrication of novel graphene-polysulfide (GPS) anode materials, which consists of conducting graphene network and homogeneously distributed polysulfide in between and chemically bonded with graphene sheets. Such unique architecture not only possesses fast electron transport channels, shortens the Li-ion diffusion length but also provides very efficient Li-ion reservoirs. As a consequence, the GPS materials exhibit an ultrahigh reversible capacity, excellent rate capability and superior long-term cycling performance in terms of 1600, 550, 380 mAh g−1 after 500, 1300, 1900 cycles with a rate of 1, 5 and 10 A g−1 respectively. This novel and simple strategy is believed to work broadly for other carbon-based materials. Additionally, the competitive cost and low environment impact may promise such materials and technique a promising future for the development of high-performance energy storage devices for diverse applications. Published version

Despite the fascinating Li storage properties of organic carbonyl compounds, e.g., high therotical capacity and fast kinetics, it is still lack of a facile and effective way that capable of large-scale producion of advanced carbonyl cathodes for Li-ion batteries (LIBs). Here, a generic strategy is proposed by combining sonication and hydrothermal techniques for scalable synthesis of high performance organic carbonyl cathodes for LIBs. A series of commercialized vat dyes with abundant electroactive conjugated carbonyl groups are confined in between the graphene layers, forming a compatible 3D hybrid architecture. The unique structure affords good Li+ ions accessibility to the electrode and short Li+ ions diffusion length. Meanwhile, each sandwiched graphene layer functions as a miniature current collector, ensuring fast electron transport throughout the entire electrode. Consequently, the cathodic performances of LIBs using the composites as electrodes, for example, Vat Green 8/graphene, Vat Brown BR/graphene, and Vat Olive T/graphene, possess high specific capacity, exceptional cycling stability, and excellent rate capability. The effect of vat dye content on the morphology, structure, and the final electrochemical performance of the composites is investigated as well. This work provides a versatile and low-cost platform for large-scale development of advanced organic-based electrodes toward sustainable energy fields.

Graphene oxide gel (GOG) possesses intrinsic three-dimensional (3D) networking architecture with large surface area and high porosity. Here, we report a novel method of fabrication of GOG by self-assembling a ferrocene-decorated graphene oxide sheets (GOS) at room temperature. Our systematic investigations reveal that Fc plays a critical role in the formation of such unique 3D architecture, as it functions as an effective interlayer cross-linker through the π–π interaction. The morphology, crystal structure, chemical bonding, porosity and thermal stability of the as-prepared GOG have been studied. This work successfully provides a facile and efficient way to form GOG and will extend the potentials of GOG as a promising electro-active material in carbon-based electronics or catalytic reactors.

An efficient method for the preparation of benzoxazole and benzimidazole covalently grafted graphene and their application as high performance electrode materials for supercapacitors is reported. The synthesis of such covalently functionalized graphene materials first involves a cyclization reaction of carboxylic groups on graphene oxide with the hydroxyl and aminos groups on o-aminophenol and o-phenylenediamine, and subsequent reduction by hydrazine. Results of Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) have confirmed that the covalent functionalization of graphene is achieved through the formation of benzoxazole and benzimidazole on the graphene sheets. The functionalized graphene materials are revealed to consist of corrugation and scrolling morphologies with less aggregation, indicating the effectiveness of functionalization in preventing restacking/aggregation of the graphene sheets. Furthermore, when applied as supercapacitor electrodes, the functionalized graphene materials exhibit good electrochemical performances in terms of high specific capacitance (730 and 781 F g−1 for benzoxazole and benzimidazole grafted graphene, respectively, at a current density of 0.1 A g−1) and good cycling stability, implying their potential for energy storage applications.

A facile and effective method for the synthesis of redox-crosslinked graphene networks is reported. This method involves the polyphosphoric acid-catalyzed cyclization reaction between the carboxylic groups on graphene oxide and the hydroxyl, amino groups on 4,6-diaminoresorcinol hydrochloride, as well as a subsequent reduction process. The obtained benzobisoxazole-crosslinked graphene networks (BBO-GNs) show a high BET surface area of 357 m2 g−1 in comparison with the reduced graphene oxide (rGO) (117 m2 g−1), due to the presence of benzobisoxazole groups that prevent the irreversible restacking or agglomeration of graphene sheets during the reduction. Another immediate and more practically meaningful benefit of introducing benzobisoxazole groups is that such functional groups could effectively provide an extra contributing channel to the specific capacity by pseudocapacitance. As a consequence, the improved performance such as significantly enhanced electrochemical capacitance is clearly demonstrated in the supercapacitor with the electrodes of BBO-GNs.

We reported resistive switching behaviors in the resistive random access memory (RRAM) devices based on the different annealing temperatures of graphene oxide (GO) film as active layers. It was found that the resistive switching characteristics of an indium tin oxide (ITO)/GO/Ag structure have a strong dependence on the annealing temperature of GO film. When the annealing temperature of the GO film was 20 °C, the devices showed typical write-once-read-many-times (WORM) type memory behaviors, which have good memory performance with a higher ON/OFF current ratio (∼10(4)), the higher the high resistance state (HRS)/low resistance state (LRS) ratio (∼10(5)) and stable retention characteristics (>10(3) s) under lower programming voltage (-1 V and -0.5 V). With the increasing annealing temperature of GO film, the resistive switching behavior of RRAM devices gradually weakened and eventually disappeared. This phenomenon could be understood by the different energy level distributions of the charge traps in GO film, and the different charge injection ability from the Ag electrode to GO film, which is caused by the different annealing temperatures of the GO film.