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The reuse of waste papers by conversion into valuable carbon materials has received considerable attention for diverse applications such as energy storage and water purification. However, traditional methods for converting waste papers into materials with suitable properties for specific applications are often complex and ineffective, involving consecutive carbonization and activation steps. Herein, we propose a simple one-step microwave (MW)-assisted synthesis for preparing waste paper-derived porous carbons (WPCs) for energy storage and water purification. Through a 30-min synthesis, WPCs with graphitic structure and high specific surface area were successfully produced. The fabricated WPCs exhibited outstanding charge storage capability with a maximum specific capacitance of 237.7 F g−1. Additionally, the WPC demonstrates a high removal efficiency for various dyes, achieving a maximum removal efficiency of 95.0% for methylene blue. The developed one-step MW synthesis not only enables the production of porous carbon from waste paper, but also offers a viable approach to address solid waste management challenges while simultaneously yielding valuable materials. [Display omitted] • Waste paper-derived porous carbons were synthesized by one-step microwave synthesis. • Within 30-min MW synthesis, graphitic and high-surface area WPCs were produced. • WPC exhibits outstanding electrochemical capacitance of 237.7 F g−1. • WPC exhibits high removal of various dyes, with maximum of 95.0% for methylene blue. [ABSTRACT FROM AUTHOR]

In this paper, carbon paper as positive electrode for vanadium redox flow battery was etched by chlorosulfonic acid with assistance of ultrasonication. Carbon layer-exfoliated, wettability-enhanced, SO 3 H-functionalized carbon paper was successfully achieved by facile treatment. The electrochemical kinetics of VO 2+ /VO 2 + redox reaction on carbon paper was significantly improved after the treatment. Carbon paper after ultrasonication-assisted treatment exhibits better electrochemical activity compared with the untreated and only-soaking samples. The cell using treated carbon paper as positive electrode shows larger discharge capacity and higher energy efficiency compared with the pristine cell. The initial discharge capacity of the cell using optimal treated carbon paper reaches 127.7 mA h, 20.8 mA h larger than that of the pristine one at 50 mA cm −2 . Furthermore, the average energy efficiency increases by 5.1% by using the treated electrode. The introduced sulfonic groups as active sites and increased surface area by etching can reduce the electrochemical polarization of VO 2+ /VO 2 + redox reaction. Moreover, the improved wettability of treated carbon paper can accelerate mass transfer of active species. Therefore, the reduced electrochemical polarization and accelerated mass transfer of active species conjointly cause the enhanced electrochemical properties of the treated carbon paper. [ABSTRACT FROM AUTHOR]

Variable renewable energy-based power is expected to increase toward a sustainable society, although the power cannot be dispatched effectively due to its intermittent nature. To accelerate renewable energy implementation, we simulated energy flows of paper mills installing wind energy and evaluated their potentials to function as energy hubs for appropriate early-stage design. We targeted 39 Japanese paper mills assumed to have thermal energy storage, wind–thermal energy converters and regional woody biomass installed, and analyzed the amount of power and heat selling and life cycle greenhouse gas emissions. The results for the paper mills were compared with conventional mills to examine effective conditions for greenhouse gas reduction. The amount of power or heat selling depended on the capacity of the paper mill and the installed equipment. Most paper mills could reduce greenhouse gas using thermal energy storage, wind energy, and woody biomass. The paper mill with the highest life cycle greenhouse gas reduction, compared with conventional mills, could achieve a 190% reduction. To function as a cogeneration energy hub, the equipment installed in paper mills should be designed according to the conditions of the paper mills and their regions. • Paper mills have potential as energy hubs by integrating variable renewable energy. • Thermal energy storage and wind–thermal energy converters were studied. • Energy flows and greenhouse gas emissions of paper mills were simulated. • Most mills could provide stable power and/or heat supplies and reduce emissions. [ABSTRACT FROM AUTHOR]

In the quest for greener and more efficient energy storage solutions, the exploration and utilization of renewable raw materials is essential. In this context, cellulose-derived separators play a central role in enhancing the performance of green energy storage devices. However, these often exhibit disadvantageous porosity and limited wet strength. Here, we demonstrate a facile approach to tailor thickness (ca. 40 μm), air permeability (0.1–200 cm3 s−1), and mechanical properties of separators by integration of up to 50 wt% microfibrillated cellulose (MFC) into paper sheets. While the MFC enhanced the formation of dense networks, these separators show a poor dimensional stability (folding and creasing) concomitant with a low strength under wet conditions, crucial for assembly and operation. Crosslinking with 1,2,3,4-butanetetracarboxylic acid (BTCA) however, led to an increase in wet strength by up to 6700 % while ensuring dimensional stability. The electrochemical performance, evaluated by impedance spectroscopy and galvanostatic cycling (7500 repetitions) showed comparable results as commercially available glass and polypropylene separators in terms of ion diffusion, charge-discharge rate performance, Ohmic loss and capacitance retention %. The approach demonstrates that disadvantages of paper-based separators in terms of dimensional stability and wet strength can be overcome by a paper technological approach using crosslinking strategies. [Display omitted] [ABSTRACT FROM AUTHOR]

• Porous nanosheet-like NiCo LDH can be grown immediately on carbon fiber paper by electrodepositon as binder free electrode for supercapacitors • The morphology and electrochemical performance can be tuned by changing the deposition potential. • The optimized electrode can deliver excellent rate performance and cyclic stability. • This work demonstrates a simple, scalable and controllable strategy for preparing binder-free electrodes for supercapacitors. Design of binder-free electrode with high performance exhibits great glamour for energy storage devices recently. Herein, nickel cobalt layered double hydroxide (NiCo LDH) has been directly grown on carbon fiber paper (CFP) by an electrodeposition method. Thanks to the porous nanosheet-like morphology of the deposits, the high conductivity of carbon fibers, as well as the strong connection between the deposits and the substrate, the optimized electrode, labeled as NiCo LDH-2/CFP can deliver a discharge specific capacitance of 878.4 F g−1 at 1 A g−1, which can increase to 1080.0 F g−1 at 20 A g−1, exhibiting excellent rate performance. Moreover, after cycled at 5 A g−1 for 5000 cycles, the capacitance of the electrode can retain 96.1%, manifesting unique cyclic stability. This work provides a new strategy for preparing high performance binder-fee electrodes for supercapacitors, lithium batteries and catalytes. In this work, we demonstrate a simple and highly controlled electrodeposition method for the construction of porous nanosheet-like nickel cobalt layered double hydroxide that are directly grown on carbon fiber paper, which shows exceptional rate and cyclic performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Along with the developing of flexible electronics, there is a strong interest in high performance flexible energy storage materials. As natural carbohydrate polymer, cellulose fibers have potential applications in the area due to their biodegradability and flexibility. However, their conductive and electrochemical properties are impossible to meet the demands of practical applications. In this study, cellulose fibers were combined with polyaniline to develop novel paper-based supercapacitor electrode material. Cellulose fibers were firstly coordinated to Cu(II) and subsequently involved in polymerization of polyaniline. Not only the mass loading of polyaniline was significantly increased, but also an impressive area specific capacitance (2767 mF/cm2 at 1 mA/cm2) was achieved. The developed strategy is efficient, environmentally friendly, and has implications for the development of cellulosic paper-based advanced functional materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In an era of modern smart technology, flexible electrodes are of great interest for different energy conversion as well as energy storage applications like solar cells, all solid-state batteries, and supercapacitors. Flexible metal oxide-based paper electrodes are advantageous in comparison to conventional electrodes due to their economical synthesis, biocompatibility, and environment-friendly characteristics. However, the electrical conductivity of paper electrodes is limited because of the insulating nature of natural fibers employed as a binder for the flexible matrix of metal oxides. The current study is an attempt to tune the electrical properties of lignocelluloses (natural fibers) and titanium dioxide (TiO 2) based paper electrodes by facile electrodeposition technique. The crystalline parts (e.g., TiO 2 , Ag, and Au) of the prepared composite sheets were characterized by XRD analysis while the surface morphology was studied by SEM. FTIR was used to characterize the organic matter in LC fibers by identifying various molecular stretching and vibrational modes of C, H, and O-containing molecules. Electric permittivity was measured as a function of electric field frequency at room temperature which revealed the value of 23. 5 (at 1 kHz) for the sample LC/TiO 2 /Ag 9000s indicating the best charge storing capability of the sample. Impedance analysis was employed to identify various charge carrier mechanisms active in the sheets. It was found through impedance analysis that there is an active diffusion-controlled impedance mechanism of Au-coated samples causing an increased conductivity via the ionic diffusion. This diffusion-controlled conduction was modeled by the Warburg element. The enhanced conductivity due to ionic diffusion makes these samples more useful as electrodes. Cyclic voltammetry (CV) measurements of the electrodeposited samples established the increase in conductive properties and efficient kinetics of LC/TiO 2 paper sheets. The current study suggests that Ag and Au-coated paper electrodes can be potential candidates for energy conversion and storage applications. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries (LSBs) are gaining attention as a potential energy storage option due to their impressive theoretical specific capacity. However, the main challenges hindering its implementation include the expansion in volume of sulfur and lithium sulfide during the conversion process of charge-discharge, the limited conductivity of the active material, and specifically, the phenomenon known as shuttle effect caused by lithium polysulfides (LiPSs). The development of high-performance LSBs have led to the need for self-supporting cathode materials that can efficiently accommodate volume expansion, build up efficient conductive pathways, and suppress shuttle effects. The poly(3,4-ethylenedioxythiophene) (PEDOT) was synthesized in situ on cellulose nanofibers (CNFs), resulting in the formation of CNF@PEDOT. Subsequently, CNF@PEDOT was combined with plant fibers (PFs) and multi-wall carbon nanotubes (MWCNTs) to fabricate a self-supporting cathode featuring a multi-scale network structure denoted as CNF@PEDOT/MWCNT/PF/S. The PFs serve as the primary backbone network, CNF@PEDOT to form the secondary conductive network, and MWCNTs act as tertiary conducting networks. In fact, the design of multi-level conductive network effectively improves the conductivity of the material, and PEDOT can further adsorb and catalyze LiPSs. The incorporation of PFs significantly enhanced the mechanical robustness of the cathode and augmented its electrolyte permeability. The self-supporting CNF@PEDOT/MWCNT/PF/S cathode exhibits an initial capacity of 1204.6 mA h g−1 when loaded with 2.4 mg cm−2 of sulfur at a rate of 0.2 C. Notably, it maintains an initial discharge specific capacity of 712.9 mA h g−1 even when the sulfur load is increased to 4.3 mg cm−2. This study presents a comprehensive framework for the development of self-supporting cathodes in LSBs. [Display omitted] • The self-supporting cathode with multi-scale network structure has been fabricated by the papermaking process. • The copious hydrogen bonds furnished by plant fibers enhance the mechanical characteristics of the material. • The efficient conductive network was formed in a self-supporting cathode by in situ polymerization of PEDOT on CNFs. • The CNF@PEDOT network with a high aspect ratio exposure of -S- functional groups for efficient anchoring of polysulfides. • The incorporation of rich multi-scale conductive network significantly improves the conductivity of cathode materials. [ABSTRACT FROM AUTHOR]

• Three-dimensional WO 2 /MoO 2 @P, N-CNTs were prepared by the Self-template method. • Highly conductive and hollow structure of WO 2 /MoO 2 @P, N-CNTs avoided aggregation of NiCo-LDH. • IMSC devices were prepared by fully screen-printed technology. • IMSCs demonstrated excellent energy density (0.0590 mWh cm−2), cycling stability (100% capacity retention after 10,000 cycles) and mechanical stability (lighting the bulb under extremely distorted conditions). In-plane micro-supercapacitors (IMSCs) have greater promise for use in flexible wearable electronics than traditional stacked configurations due to their ease of integration and conformability. Nickel-cobalt layered double hydroxide (NiCo-LDH) has garnered significant interest as a stellar material for supercapacitors because of its affordable price, regular morphology, and high theoretical capacity. Unfortunately, the intrinsic poor conductivity of LDH materials prevents supercapacitors from achieving long-term stable cycling and the desired energy density. This research successfully applies the self-templated approach to prepare carbon nanotubes (CNTs) with heterogeneous architectures and numerous phase interfaces, thereby mitigating this disadvantage. Carbon nanosheets adorned with WO 2 and MoO 2 nanoparticles assemble the CNT with a typical three-dimensional structure. When combined with LDH in a suitable ratio, the composite electrode's conductivity significantly improves, providing increased capacity and cycling stability. Compared to commercial CNTs, the larger size of the prepared WO 2 /MoO 2 @P, N-CNTs serves a superior supporting and connecting role, thereby preventing the NiCo-LDH from aggregating. Under the best conditions, the composite electrode demonstrates a capacity of 1237 C/g at 1 A g−1 and an optimal capacity retention of more than 92%. For the IMSC devices, the composite materials as the positive electrode achieve an energy density of 0.0590 mWh cm−2, and no capacity degradation is observed after 10,000 cycles. In addition, bending tests have demonstrated the mechanical stability of the IMSCs. Therefore, this strategy of mixing highly conductive WO 2 /MoO 2 @P, N-CNTs can effectively improve the conductivity of the composite material and the mechanical properties of the overall device. Furthermore, this concept can be further extended to the preparation and application of other wearable devices. [ABSTRACT FROM AUTHOR]

Hierarchical composites (CFP–PANI) of carbon fiber papers (CFP) and polyaniline (PANI) have been facilely prepared by in-situ polymerization of aniline monomers on the surface of CFP films, which were simply obtained by low-cost carbonization of widely used filter paper. The wood–celluloses, which serve as the main component and the backbone of filter paper, are key raw materials for fabricating energy-related devices. Carbon fibers with porous structure were formed after the cellulose fibers were carbonized at high temperature. And cross-linked conductive networks have been achieved with the carbon fibers connected with each other. Different amounts of aniline monomer were in-situ polymerized on the surface of CFP, resulting in the formation of three-dimensional (3D) free-standing composite paper of CFP–PANI. Compared with pristine CFP and pure PANI, greatly enhanced electrochemical performance of CFP–PANI composite has been successfully achieved, including high specific capacitance (334 F g −1 ), good cycling stability as well as excellent rate capability. These superior electrochemical properties of CFP–PANI composite paper can be ascribed to the hierarchical structure of CFP, strong interaction between CFP and PANI, as well as the synergistic capacitance performance of CFP films and PANI nanoparticles, suggesting CFP–PANI composite paper thus simply prepared is good candidate for applications in high performance energy storage fields. [ABSTRACT FROM AUTHOR]

Organic molecule stabilized manganese stannate (MnSnO 3) perovskite nanoparticles were synthesized using a complexion strategy route. The Rietveld refinement analysis confirmed the formation of orthorhombic structure of manganese stannate with the space group of Pnma. Free standing manganese stannate electrode was fabricated on paper based flexible substrate and investigated the electrochemical performances. The maximum specific capacitance and areal capacitance delivered by electrode were ∼ 183 F/g and ∼ 487 mF/cm2, respectively, at the current density of 0.2 A/g, with an excellent capacitance retention ∼ 93% for 103 cycles at 0.6 A/g. A symmetric supercapacitor was fabricated using the MnSnO 3 as active material on positive and negative electrodes in solid state gel electrolyte configuration. The device achieved the specific capacity value ∼ 156 mAh/g at 0.1 A/g with the energy density and power density of ∼ 10 Wh/kg and ∼ 22 kW/kg, respectively, at 0.5 A/g. These results suggested that manganese stannate nanoparticles are promising candidates for high-performance supercapacitor application. [Display omitted] • Organic molecule stabilized manganese stannate perovskite nanoparticles. • Flexible Au-coated paper based free-standing electrode and symmetric device were fabricated for supercapacitor applications. • Diffusive control mechanism dominated the overall charge storage process. • The fabricated device exhibited excellent stability for energy and power storage performance. [ABSTRACT FROM AUTHOR]

• The 1D/2D MnO 2 /MXene heterostructures generate built-in electric fields that greatly accelerating the ionic and electronic diffusion/transport kinetics. • The synergistic mechanism generated by 1D/2D heterostructures achieve the balance between high energy storage activity and high active substance proportion of MnO 2 /MXene flexible electrode. • The quasi-solid-state FZIBs with MnO 2 /MXene paper-like film provide high total specific capacity and stability in flexible applications. Paper-like flexible electrode plays a critical importance role in booming the development of flexible energy storage devices. One-dimensional manganese dioxide (1D MnO 2) shows immense advantage in flexible zinc-ion batteries (FZIBs) on account of renowned tunnel crystal structure and high operating voltage. However, inherent inferior electrical conductivity and sluggish reaction kinetics seriously hinder the practical application of FZIBs, resulting in unsatisfactory rate capability and cycle performance. Herein, 1D/2D MnO 2 /MXene-5 heterostructure materials were constructed by electrostatic self-assembly, which were then prepared into paper-like membrane with high energy storage active substance ratio (95.2 %) towards high capacity and ultrastable FZIBs. The built-in electric field induced by the heterostructure accelerates the electron transfer, reduces the charge transfer resistance and promotes ion diffusion, enabling the 1D/2D phase collaboration to improve the zinc ion storage of the paper-like electrode. The design achieves a high total specific capacity (based on the total cathode mass) of 314.7 mAh g−1 at 0.1 A g−1 and ultrastable of 8000 cycles at 5 A g−1 with a retention of 81.1 %. Remarkably, quasi-solid-state FZIBs with MnO 2 /MXene-5 membrane can deliver an outstanding reversible capacity of 273.5 mAh g−1 at 0.1 A g−1 and maintain 500 cycles at 1 A g−1 across various bending angles without decay, demonstrating excellent stability. This work provides a novel approach for the targeted design of self-standing flexible electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

Cellulose paper is considered to be a promising substrate of energy materials for energy storage device due to its flexible, porous, renewable, degradable, and environmental-friendly feature. However, the large weight and low conductivity of cellulose fibers limit the specific capacitance and energy density of the paper electrodes. Converting cellulose fibers into conductive carbon fibers (CCF) by high temperature carbonization is an effective strategy for improving the electrochemical performance of paper electrodes. But the brittleness of carbonized paper limits its application in flexible supercapacitors. In addition, stable loading of energy materials on CCF is another challenge. Here, KNO 3 in-situ etching activation method is used to construct the embedded structure of transition-metal oxides (TMOs) on CCF. And the embedding degree of TMOs on CCF can be adjusted by controlling the amount of KNO 3. The embedded structure releases the mechanical stress from bending of CCF, endowing good flexibility for carbonized paper. In addition, embedded structure can anchor TMOs into CCF, and increase the porosity and specific surface area of CCF, promoting a rapid ion diffusion and electron transport for high capacitance contributions. The KNO 3 -etched Co 3 O 4 @CCF paper as an electrode exhibits a high volume specific capacitance of 72.3 F cm−3 at current density of 0.5 mA cm−2 (more than three times higher than that of Co 3 O 4 /CCF paper) and shows good rate capability (capacitance retention of 83.3% with 10 times current density) and long lifetime (charge-discharge stability of 94.8% after 10000 cycles). Even in bending state, the composite paper still maintains stable electrochemical performances, which can broaden potential application in flexible supercapacitors. [Display omitted] • A flexible carbonized paper was fabricated for supercapacitors electrode. • KNO 3 in-situ etching activation method was used to embed TMOs into CCF. • The embedded structure released the mechanical stress from bending of CCF. • The embedded structure increased the porosity of CCF for rapid ion diffusion. • The flexible carbonized paper exhibited excellent electrochemical performances. [ABSTRACT FROM AUTHOR]

The development of Fe 2 O 3 with high conductivity and energy density is crucial for practical utilizations of supercapacitors. Here, we demonstrated the preparation of novel Fe 2 O 3 /graphene oxide paper (Fe 2 O 3 /GP) hybrid electrode for high density supercapacitors. Due to the characteristic features of large surface areas and fast electron transportation, the specific areal capacitance of the Fe 2 O 3 /GP was around 3.08 F cm −2 at the charge-discharge current density of 5 mA cm −2 , which is nearly 14 times of the Fe 2 O 3 /carbon paper (Fe 2 O 3 /CP, 0.22 F cm −2 ). More importantly, the Fe 2 O 3 /GP hybrid electrode also retained about 95% of the initial capacitance after long-term cyclic process. These findings would help us to develop high effective and stable materials for energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract The introduction of surface functional groups onto graphite can provide additional pseudocapacitance for supercapacitors. However, the compensation for the loss of electrical conductivity arising from the destruction of the π-π conjugation remains a big challenge. Here, the graphite paper is electrochemically oxidized first, followed by the mild reduction using hydroiodic acid to afford the largely exfoliated and moderately reduced sample (noted as MOGP-4). The as-prepared MOGP-4 not only has the abundant oxygenous groups, but also preserves the highly conductive network (sp2 carbon). Owing to the good conductivity (1.14 × 103 S m−1), MOGP-4 exhibits a high rate capability of 93% (from 18.3 mF cm−2 to 17 mF cm−2) as the current density increases from 0.5 to 10 mA cm−2 and predominant cycling performance. Furthermore, the flexible solid-state supercapacitors (SSCs) based on MOGP-4 with different sizes are assembled and deliver excellent durability, high flexibility and superior rate capability. The high electrochemical performances of the as-fabricated supercapacitors should envision promising applications for energy storage devices. Graphical abstract Image 1 highlights Graphite paper (GP) row material is low-cost, commercial, large-area and flexible. GP is electrochemically oxidized in mixed acids and then mildly reduced by HI. The strategy can introduce oxygenous groups and preserve high conductivity of GP. The fabricated SCs have high rate capability, stability and coulombic efficiency. [ABSTRACT FROM AUTHOR]

• 1T-MoS 2 was applied as a flexible and functional "spacer" to hybridize with Ti 3 C 2 T X MXene, forming flexible capacitive freestanding films. • The insertion of electrically neutral pseudocapacitive could mitigate the restacking of Ti 3 C 2 T X MXene layers and improves the capacity of the composite paper. • The supercapacitor fabricated with acidic gel electrolyte and composite electrode with randomly stacked MXene and 1T-MoS 2 in a mass ratio of 6:1 demonstrated optimal performance. In the case of increasing shortage of non-renewable resources, developing high-efficiency and high-capacity energy storage devices is critical. Supercapacitors have the potential of high-efficiency and high-capacity. MXene and 1T-MoS 2 are two kinds of high performance pseudocapacitive materials. However, the stacking and aggregation of MXene nanosheets greatly reduce its capacity. The poor conductivity of 1T-MoS 2 also limits the full expression of its excellent pseudocapacitive performance. A flexible MXene/1T-MoS 2 composite paper electrode is designed and prepared in this work where the restacking of MXene can be relieved and the whole electrode maintains the conductivity. The interior stacking structure of MXene and 1T-MoS 2 in the composite paper, as well as the gel electrolyte type are explored. The device constructed with the electrode composed of randomly stacked MXene and 1T-MoS 2 (mass ratio 6:1) and acidic electrolyte (PVA/H 2 SO 4 gel electrolyte) demonstrates the optimal performance. The specific areal and volumetric capacitances reach 561.2 mF cm−2 and 1268.17 F cm−3 at the current density of 0.8 mA cm−2 respectively, outperforming most of the previously reported values for MXene based supercapacitors tested in gel electrolyte. The supercapacitor has excellent deformation durability and long cycle stability, demonstrating promising prospect in future flexible electronics. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Various carbon nanotube-based devices are developed for solar energy utilization. • The water evaporation system can generate freshwater (1.28 kg m−2h−1). • The solar-thermoelectric system can output a voltage and charge a cellphone. • The supercapacitor performs an areal specific capacitance of 19.6 mF cm−2. • The hybrid energy system can produce freshwater, generate and store electric power. Nowadays, multi-functional systems driven by solar energy have been explored to alleviate the crisis of energy and freshwater scarcity. However, it remains a great challenge to integrate multi-functions into one hybrid system with a monolithic material, which can harvest, convert and store solar energy synergistically. Here, we firstly propose a multi-functional carbon nanotube paper, which starts from a material level to solve these problems. The carbon nanotube paper is fabricated by vacuum filtration. It exhibits high efficiency of solar-thermal conversion. Secondly, three types of energy conversion/storage systems (e.g., solar-thermal evaporation system, solar-thermoelectric generation system, and supercapacitor) are constructed based on the carbon nanotube paper, which extend the research to a device level. The solar-thermal evaporation system shows an evaporation rate of 1.28 kg m-2h−1 under simulated sunlight irradiation of 1 kW m−2. The solar-thermoelectric generation system demonstrates a stable electric power generation with an output voltage of 100 mV under light irradiation of 1 kW m−2. The supercapacitors perform the energy storage function with an areal specific capacitance of 19.6 mF cm−2. These devices and systems can be used in freshwater generation (0.84 kg m-2h−1, sunlight irradiation of 1 kW m−2), water purification/desalination (inorganic ions rejection larger than 99.9%) and portable solar charging system (maximum output voltage of 5 V). Finally, a hybrid energy system is innovatively proposed from the system level to simultaneously produce freshwater, generate and store electric power. Through the synergetic coupling of solar conversion and storage technologies, the hybrid energy system can supply sustainable freshwater and electricity for remote areas in daily life, highlighting the superiority of multi-energy (thermal energy, electrical energy, and electrochemical energy) complementary. [ABSTRACT FROM AUTHOR]

Herein we reported a novel routine to easily access graphene/polyaniline paper (GPp) as supercapacitor electrodes through controlled in-situ polymerization followed by roll coating. According to this routine, the load fraction of PANI can be easily controlled by feed ratio of aniline to GO. In the resulting GPp, PANI nanoarrays anchored graphene nanosheets and PANI nanofibers throughout the bulk coexist, and the former construct a three-dimensional network. As a result, the GPp as a freestanding electrode exhibits excellent electrochemical properties. It can deliver a high capacitance up to 838 F/g at a current density of 1 A/g, while keeps high retention of 93.7% at 10 A/g over 5000 cycles. Kinetics analysis shows that the GPp stores both surface capacitance and diffusion capacitance, but the former dominates the latter. [ABSTRACT FROM AUTHOR]

Electro-conductive paper-based products can suit the needs of various end-use applications, e.g., antenna and energy-storage devices. Here, the concept of using stilbene-triazine sulfonic acid sodium salts (STAS) as dopants for enhancing the conductivity of polypyrrole-paper composites and mitigating the decay of conductivity was demonstrated. Noticeably, the combined use of hexa-sulfonic STAS and 9,10-anthraquinone-2-sulfonic acid sodium salt (AQSAS) as dopants delivered significant enhancement of conductivity. Meanwhile, the decay of conductivity during storage was substantially mitigated. Moreover, the effectiveness of hexa-sulfonic STAS was much more pronounced than the other two types of STAS, i.e., di-sulfonic STAS and tetra-sulfonic STAS. [ABSTRACT FROM AUTHOR]

An in-situ and controllable redox deposition method has been applied to prepare binder-free MnO 2 nanosheet array-decorated carbon paper as negative electrode for vanadium redox flow batteries (VRFB). Electrochemical performance of electrode depends on amount and uniform distribution of MnO 2 on carbon paper, which were controlled by solution pH, KMnO 4 concentration, and deposition time. Modified carbon paper (CPA-05-30) with a uniform MnO 2 nanosheet coating layer was obtained in 0.05 M KMnO 4 + 0.5 M H 2 SO 4 solution for 30 min. CPA-05-30 presents the most excellent electrocatalytic performance for V3+/V2+ redox reaction. On CPA-05-30, charge transfer and diffusion processes for V3+/V2+ redox reaction are accelerated as a result of MnO 2 nanosheet with high catalytic activity and excellent hydrophilcity. Therefore, loading MnO 2 on carbon paper improves electrochemical activity V3+/V2+ redox reaction. Moreover, in charge-discharge test, the cell using CPA-05-30 as negative electrode shows higher discharge capacity and better capacity retention at 50 mA cm−2 for 50 cycles in comparison with pristine cell. It indicates that MnO 2 nanosheet can efficiently increase electrolyte utilization. At 100 mA cm−2, energy efficiency of the cell using CPA-05-30 is 66.4%, which is 6.0% higher than that of pristine cell. MnO 2 nanosheet decorated carbon paper shows excellent electrochemical properties for energy storage application, which evidences its potential application in VRFB. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Flexible micro-supercapacitors (FMSCs) are promising candidates for portable and on-chip energy storage due to their miniaturization, lightweight and high-security. Till now, FMSCs still suffer from several limitations, such as complex fabricating process, low areal energy storage, and short cycling lifetime, badly inhibiting its wider on-chip integrated applications. Here, we directly employ an easy-processing spray coating of the Ti 3 C 2 T x MXene conductive inks to massively fabricate the paper-based all-solid-state FMSCs. Instead of traditional noble metals Au as current collector, the sprayable and highly conductive Ti 3 C 2 T x MXene interdigitated electrodes serve the dual function of the active materials and current collection. Based on it, we develop an all-solid-state FMSC by employing polyvinyl alcohol & H 2 SO 4 gel-like solid-state electrolyte and self-flowed polydimethylsiloxane encapsulated layer. With further optimizing the geometric configurations of interdigitated electrodes, the as-prepared FMSCs exhibit high areal capacitance of 23.4 mF cm−2 and excellent rate-capability of 81.4%. Moreover, these paper-based FMSCs also demonstrate outstanding cyclic capability of 92.4% capacitance retention after 5000 cycles, along with remarkable flexibility. Consequently, we believe that this innovative strategy will open new avenues for easily and largely fabricating various FMSCs to further promote the integration of portable and on-chip energy storage systems. Graphical abstract Image 1 Highlights • It can easily achieve large-scale manufacturing and integration. • Ti 3 C 2 T x MXene acts as both the active material and current collection. • The configurations are optimized to obtain the best electrochemical performance. • Flexible paper-based micro-supercapacitors with excellent performance are obtained. [ABSTRACT FROM AUTHOR]

Abstract The electrode materials with large surface area and high porosity are predominant to enable the energy storage properties of electrochemical supercapacitors. Herein, lab-waste tissue paper templated trimanganese tetroxide hollow microtubes (Mn 3 O 4 HMTs) with high porosity on their walls were synthesized via a facile biomorphic method. Initially, aqueous manganese precursor was impregnated onto the surface of cellulose fibers by means of evaporation of water molecules. After thermal treatment under ambient atmosphere, the cellulose fibers were removed, which led to the formation of Mn 3 O 4 HMTs. The morphology, crystallinity and surface area of the prepared Mn 3 O 4 HMTs were examined by FE-SEM, XRD and BET analyses. When tested in aqueous alkaline electrolyte, the as-prepared Mn 3 O 4 HMTs delivered a maximum specific capacitance of 51.7 F g−1 at the current density of 1 mA cm−2 with good rate capability of 64.6% at high current density of 10 mA cm−2, which is due to the high porosity that enables an effective penetration of electrolyte ions. After 2000 cycles, the porous Mn 3 O 4 HMTs demonstrated good cycling stability of 57.1% at a current density of 5 mA cm−2. This facile method for the preparation of hollow structured materials could provide a deep insight into novel pseudocapacitive materials. Graphical abstract Image 1 Highlights • Mn 3 O 4 hollow microtubes (HMTs) were prepared using waste tissue papers as a template. • The Mn 3 O 4 HMTs exhibited large surface area and multilayered pores. • The as-synthesized material delivered a superior capacitance and good cycling stability. [ABSTRACT FROM AUTHOR]

A facile hydrothermal method is utilized to produce nanostructured NiCo 2 S 4 arrays on carbon fiber paper with controlled morphologies to study the effect of morphology on their electrochemical performance in supercapacitors. Specifically, NiCo 2 S 4 solid nanofiber, nanotube, and hollow nanoneedle of the same crystalline structure are synthesized by controlling the conditions of the hydrothermal synthesis. Among the three different morphologies studied, the hollow nanoneedle of NiCo 2 S 4 shows the highest capacity and the longest cycling life, demonstrating a specific capacitance of ~1154 F g −1 at a charge–discharge current density of 1 A g −1 and negligible capacity loss after 8000 cycles (at a rate of 10 A g −1 ). This high performance is attributed to the unique nanostructure of the hollow nanoneedle, suggesting that the morphology of NiCo 2 S 4 plays a vital role in determining the electrochemical performance. Further, an asymmetric capacitor consisting of NiCo 2 S 4 hollow nanoneedle electrode and a tape-cast activated carbon film electrode achieves an energy density of ~17.3 Wh kg −1 at 1 A g −1 and a power density of ~0.2 kW kg −1 at 20 A g −1 in a voltage range of 0–1.5 V, implying that it has a great potential for a wide variety of practical applications. [ABSTRACT FROM AUTHOR]

A free-standing, highly flexible and conductive graphene paper (GrP) was fabricated via a simple, green, and inexpensive method. The fabrication process starts with electrochemical exfoliation of graphite as partially oxidized graphene suspension, which is then vacuum-filtered and air-dried. The procedure does not warrant any binders, toxic and corrosive agents, or high temperature. The mechanically stable GrP has excellent tensile strength of 52.3 ± 2.3 MPa at peak elongation of 5.1 ± 0.4%; ultralow sheet resistance of 2.2 Ω sq −1 , which is highly stable changing by only ∼4% even after 1000 consecutive bending cycles at 10 mm bending radius; and high electrical conductivity of 3.85 × 10 5  S m −1 . The GrP also possesses high specific capacitance of 195.8 F g −1 at 1 mV s −1 in 1 M H 2 SO 4 as electrolyte at room temperature with Pt wire and Ag/AgCl as counter and reference electrodes, respectively. Moreover, the GrP can reusably absorb large amounts of oils and organic solvents. This environmentally friendly GrP fabrication method is of low cost and can be used for large-scale fabrication for applications such as energy-storage devices, flexible/wearable electronics, and removal of oil or toxic organic spills. [ABSTRACT FROM AUTHOR]

[Display omitted] • Aramid-based energy storage capacitor was synthesized by a convenient method. • Electrical breakdown strength was optimized by the interface engineering. • Good dielectric constant thermal stability from RT to 300 °C was achieved. • Our finds promoted the energy storage capacitors in commercial use. Polymer-based dielectric energy storage capacitors show more potential than conventional rigidity ceramic-based capacitors. Recent studies were classified into two categories: the excellent room temperature performance in poly (vinylidene fluoride) (PVDF) systems and the enhanced thermal stability in polyimide-based systems. Only now, however, both of them are still far from commercial use because of their inferior heat resistance or poor processability. By adding BaTiO 3 (BT) particles in maturely used aramid nanofibers, we synthesized the aramid nanofiber (ANF)/BT-based flexible paper capacitors through a convenient industrialized technology in this work. Due to the intrinsic laminated structure of ANF and the uniform distribution of BT particles, the composite film with BT addition of 8 vol% exhibits outstanding dielectric thermal stability. With the help of the interfacial resistance in the organic–inorganic interface, which protected the ANF matrix from being breakdown too early by optimizing the electrical field distribution, a high and stable energy storage density of 6.70 J/cm3 was obtained in ANF/BT5. In addition, excellent energy storage frequency stability with ultrafast discharge speed was also achieved. This work offered a highly repeatable way to synthesize commercially used flexible capacitors, bridging the lab investigation and commercial use in high-power density energy storage polymers. [ABSTRACT FROM AUTHOR]

Due to highly conducting and extraordinary stable nature, carbon based materials expand the arms of energy storage devices in terms of supercapacitor. Hence, emphasis has been made to use flexible and free-standing multi-walled carbon nanotubes (MWCNTs) bucky paper synthesized by chemical vapor deposition for electrochemical supercapacitive electrode. The high specific capacitance of 270 F/g (2 mV/s) with superb stable behavior (88% at 10000 cycles) of bucky paper has promised as decent electrode in energy storage application. Aqueous symmetric supercapacitor (ASSC) device developed through bucky paper exhibits voltage frame of 1.6 V yielding specific capacitance of 91 F/g along with specific energy of 32 Wh/kg at a current density of 1 mA/cm 2 with trustworthy stability of 107% at 6000 cycles. The hands-on practicability to light up a red LED offers its promising approach in energy storage domain. [ABSTRACT FROM AUTHOR]

The development of renewable energy sources minimizes the burning of fossil fuels for clean and green environment. Electrochemical energy storage/conversion device pays a way towards sustainable development that concludes an emerging field in the trends of the research community. Prominently, the functional materials with suitable structure and property determine the performance and durability of the devices. In recent times, graphene with its tremendous properties play a major role in electrochemical energy device applications. Meanwhile, the graphene-based electrodes were fabricated by various coating techniques on existing electrodes that utilized for energy device fabrication. Apart from these, it is also fabricated in a paper like a form (self-supported or free-standing) with its remarkable high conductivity, flexibility, robustness and electrochemical behavior which have been nominated for fabrication of flexible energy devices. Paper-like electrodes become an emerging field to fabricate a light-weight and flexible electronic devices for future prospects. Thus, we have summarized a synthetic strategy of graphene paper and its properties that potentially focused on flexible device fabrication in both the energy storage and conversion system. Hence, this review boosts up the forthcoming researchers to enhance the device performance with interrelating free-standing graphene and other host material. Number of publications from 2009 to 2018 based on free-standing graphene-paper in energy device applications gathered from Web of Science database search engine. Image 10612 [ABSTRACT FROM AUTHOR]

Abstract Zn/Ce redox flow battery (ZRFB) is emerging as a promising technology to store large amount of energy economically and efficiently, wherein a highly efficient positive electrode with a continuous and fast electronic and ionic transportation path is urgently desired. The unique nanostructure of reduced graphene oxide (RGO) paper electrode is prepared by a simply chemical reduction method, which facilitates transference of the electron and Ce3+/Ce4+ at the electrolyte/electrode interface. Thus ZRFB exhibits superior extent of charge (81.0%) and energy efficiency (71.3%). The results show RGO paper is a good candidate for positive electrode of ZRFB. Highlights • The RGOC paper possesses good flexibility with a porous structure. • The C/O ratio of RGOC is different from that of RGOT. • The activity of RGOC towards Ce3+/Ce4+ is better than that of RGOT. [ABSTRACT FROM AUTHOR]

In this study, we explored the facile and quick dry transfer method to fabricate a paper-based electrode for flexible printed energy storage system. The conventional Ag nanoparticle suspension with high solid contents above ~50 wt% was confirmed to be deposited on a super hydrophobic polyethylene terephthalate (SHP-PET) substrate without a special ink formulation or surface treatment of substrate. The silver nanoparticle (AgNP) layer on the SHP-PET was able to be transferred only onto the toner-printed region of the paper substrate during a simple lamination process, thereby realizing the patterned AgNP conductive lines on the paper substrates. The AgNP/toner/paper electrodes were highly robust, showing no deterioration in conductivity after taping for 100 times. Moreover, the AgNP/toner/paper electrodes successfully functioned as flexible electrodes; thus, light emitting diodes connected to the AgNP/paper electrodes could be operated under folding deformation without significant loss of brightness. As a potential application in flexible energy storage systems, a flexible supercapacitor based on the AgNP/toner/paper electrodes as the current collector was also demonstrated; it showed an excellent power density of 10.79–16.64 kW/kg and energy density of 1.85–4.65 Wh/kg. [ABSTRACT FROM AUTHOR]

Abstract: 3D carbon materials-supported MnO2 have promising application in energy storage as supercapacitor electrode materials. Here, we demonstrate a simple and scalable method to fabricate 3D carbon paper-supported MnO2 nanosheets, which can be used as supercapacitor electrode materials with low cost and high capacitance performance. MnO2 nanosheets with thickness about a few nanometers are grown on the carbon paper substrate through the reaction between aqueous KMnO4 and carbon. With the present method, the self-supported MnO2 composites can be fabricated into supercapacitor electrodes directly without any binder and conductive agents. It is found that MnO2 content in the composites increases with the increasing of KMnO4 concentration. The supercapacitor based on the hybrid with a MnO2 content of 7.9% exhibits the largest specific capacitance of 306.6 F g−1 at 0.5 A g−1, and a high power density of 67.8 kW kg−1 at the maximum current density of 300 A g−1. Moreover, the supercapacitors exhibit capacitance retention above 95% after 6000 cycles, demonstrating high stability of the carbon paper-supported MnO2 nanosheets for supercapacitors. Such 3D carbon paper-based architectures have promising application in energy storage devices with high power density and stability. [Copyright &y& Elsevier]

[Display omitted] • A method for fabricating integrated multi-electrodes inside a single sheet of paper. • A paper used in two dimensions used as a three-dimensional scaffold. • The control of the equivalent circuit without changing external circuits and wires. Paper is an excellent substrate for flexible devices due to its various advantages such as flexibility, porosity, lightness, and thinness. Its inherent characteristics can be also exploited to overcome the limitations of conventional substrates, such as weak adhesion and large mass densities. Here, we propose a method for fabricating vertically integrated multi-electrodes within only a single sheet of paper. Despite the randomly distributed fibrous networks in a paper, the multi-layered electrodes were uniformly formed and completely separated by applying a removable hydrophobic wax barrier confinement inside a single sheet of paper. The integrated multi-layer electrodes inside a single sheet of paper mean that conventional two-dimensional planes can be used as three-dimensional scaffolds. The highly integrated electrodes and circuit systems are located within only a sheet of paper, making a new possibility to design maximizing the energy storage performance, integrated circuit systems, and significantly decreasing the thickness of the system without external complex structure. In consequence, this unique platform can circumvent most of the fabrication challenges related to two-dimensional energy storage sheets. [ABSTRACT FROM AUTHOR]

• In-situ growth of MoS 2 over MnCO 3 inhibits formation of Mn-oxides/hydroxide. • MnCO 3 transforms to Mn(OH) 2 in aqueous KOH and stores charge by redox processes. • Mn(OH) 2 and MoS 2 afford low diffusion and charge transfer resistances, respectively. • MnCO 3 @MoS 2 hybrid utilized as negative electrode in asymmetric supercapacitor. This article puts forward a novel approach of combining the battery-type charge storage material, Mn(OH) 2 , indirectly with the two-dimensional material, MoS 2 , to develop the composite MnCO 3 @MoS 2 (designated as MCMS). A single-step facile hydrothermal method is described here for the synthesis of MCMS on a low-cost graphite substrate. Furthermore, this as-synthesized binder-free electrode is utilized as the negative electrode of an all-solid state asymmetric alkaline supercapacitor, employing NiCo 2 O 4 as the high specific energy positive electrode material. The overall asymmetric cell is shown to achieve a high specific energy of 48.97 W.h.kg −1 at 600 W.kg −1 and a high specific power of 12 kW.kg −1 at 11.33 W.h.kg −1, within a potential window of 1.2 V. Also, the composite electrode notably retains 86.5% of its gravimetric discharge capacity after 10,000 cycles with complete retention of its coulombic efficiency. The present work contributes to the development of a facile strategy for the preparation of non-carbonaceous hybrid materials suitable for high specific energy negative electrodes. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries have remarkably high theoretical specific capacity as promising candidates for next-generation energy storage. However, the “polysulfides shuttle” effect hampers its commercial application. Here, we use a kind of rice paper as a raw material to get inorganic oxides doping carbon felt by the facile carbonization method, and then modified by a simple coating process using poly (fluorenyl ether ketone) and Super P slurry. The special structure of the carbon felt derived from rice paper and its modified layer endow the final electronic conductive interlayer with inherent polysulfides absorbents and ion Coulombic repulsion functions, respectively, which show synergistic effect for trapping polysulfides. As an interlayer of Li-S batteries, the obtained carbon felt/poly (fluorenyl ether ketone)& Super P (CFSS) interlayer shows excellent electrochemical performance in improving specific capacity and decreasing polarization. The batteries with CFSS interlayer exhibit a high capacity of 837 mA h g −1 at 2.0 C and a high initial capacity of 1073.4 mA h g −1 and good capacity retention of 824.5 mA h g −1 after 500 cycles at 0.5 C. CFSS interlayer also shows excellent anti-self-discharge performance. Therefore, the simple and economical CFSS interlayer can be considered as a promising component for high performance Li-S batteries. [ABSTRACT FROM AUTHOR]

Mechanically robust graphene papers with both high gravimetric and volumetric capacitances are desired for high-performance energy storages. However, it’s still a challenge to tailor the structure of graphene papers in order to meet this requirement. In this work, a kind of chemical-reduction-tailored mechanically-robust reduced graphene oxide/carbon nanotube hybrid paper has been reported for high-performance electrochemical capacitive energy storages. Gallic acid (GA), as an excellent reducing agent, was used to reduce graphene oxide. Through vacuum filtration of gallic acid reduced graphene oxide (GA-rGO) and carboxylic multiwalled carbon nanotubes (MWCNTs) aqueous suspensions, mechanically robust GA-rGO/MWCNTs hybrid papers were obtained. The resultant hybrid papers showed high gravimetric capacitance of 337.6 F g −1 (0.5 A g −1 ) and volumetric capacitance of 151.2 F cm −3 (0.25 A cm −3 ). In addition, the assembled symmetric device based on the hybrid papers exhibited high gravimetric capacitance of 291.6 F g −1 (0.5 A g −1 ) and volumetric capacitance of 136.6 F cm −3 (0.25 A cm −3 ). Meanwhile, it exhibited excellent rate capability and cycling stability. Above all, this chemical reduction tailoring technique and the resultant high-performance GA-rGO/MWCNTs hybrid papers give an insight for designing high-performance electrodes and hold a great potential in the field of energy storages. [ABSTRACT FROM AUTHOR]

Cellulose paper-based energy storage devices have spurred significantly intrinsic advantages compared with the traditional batteries due to environmental benignity, recyclability and easy processing. In this work, the binary functional materials, which contains linear N-doped carbon nanotube (N-CNT, one-dimensional) and spherical C-coated MoS 2 (MoS 2 @C, zero-dimensional), are embedded into the porous recycled paper (RP, two-dimensional) derived from wastepaper via a facile and low-cost vacuum filtration method, and then the N-CNT/MoS 2 @C/RP film (N-M-RP film) featuring a unique compacted “point-line-plane” structure is obtained. In favor of the synergistic effect of high-conductive N-CNT, high-capacity MoS 2 @C and porous RP network, the prepared freestanding N-M-RP film presents a high strength of 35.2 MPa and a comparably low sheet resistance of 127.39 Ω sq −1 , and as an anode material for LIBs, the N-M-R film delivers a high reversible capacity, good cycling performance, superior rate capability and excellent electrochemical kinetics. Besides, the synergistic effect of “point-line-plane” structure on the improved electrochemical performances is also investigated. All the results indicate that the N-M-RP film comprised of 0D-1D-2D materials could be a potential candidate as a freestanding anode for LIBs. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy)/cobalt oxide (Co 3 O 4 )/carbon paper (CP) ternary composites prepared by potentiodynamic electropolymerization of pyrrole monomers onto flower-like Co 3 O 4 (f-Co 3 O 4 ) nanoparticles coated on CP (PPy/f-Co 3 O 4 /CP) were studied serving as electrode materials for supercapacitor applications. The f-Co 3 O 4 with unique porous morphology on CP was first obtained by drop casting Co 3 O 4 ethanol suspensions onto CP. Ball-like Co 3 O 4 (b-Co 3 O 4 ) with dense structure was also prepared for comparison. The electrochemical results including cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) in 2.0 M KOH aqueous solution revealed that the PPy/Co 3 O 4 /CP ternary composites exhibited superior supercapacitive performances than both f-Co 3 O 4 /CP and b-Co 3 O 4 /CP. Specifically, a specific capacitance of 398.4 F/g was obtained for the PPy/f-Co 3 O 4 /CP, much higher than that of 40.9 and 22.0 F/g for f-Co 3 O 4 /CP and b-Co 3 O 4 /CP, respectively. The electrochemical impedance spectroscopy studies suggested that better capacitive properties in PPy/f-Co 3 O 4 /CP were attributed to the pseudocapacitive contributions from the PPy nanocoating and greatly reduced charge transfer resistance in the composites. PPy/f-Co 3 O 4 /CP also displayed an excellent cycling stability with negligible capacitance loss after 1000 cycles. [ABSTRACT FROM AUTHOR]

With the rapid expansion of the flexible electronics market, it is critical to develop high-performance flexible energy storage electrode materials. Cellulose fibers, which are sustainable, low cost, and flexible, fully meet the requirements of flexible electrode materials, but they are electrically insulating and cause a decrease in energy density. In this study, high-performance paper-based flexible electrode materials (PANI:SSA/Zr-CFs) were prepared with cellulose fibers and polyaniline. A high mass loading of polyaniline was wrapped on zirconia hydroxide-modified cellulose fibers under metal-organic acid coordination through a facile in situ chemical polymerization process. The increase in mass loading of PANI on cellulose fibers not only improves the electrical conductivity but also enhances the area-specific capacitance of the flexible electrodes. The results of electrochemical tests show that the area specific capacitance of the PANI:SSA/Zr-CFs electrode is 4181 mF/cm2 at 1 mA/cm2, which is more than two times higher than that of the electrode with PANI on pristine CFs. This work provides a new strategy for the design and manufacture of high-performance flexible electronic electrodes based on cellulose fibers. [ABSTRACT FROM AUTHOR]

Wrinkled-paper-like ZnCo 2 O 4 nanoflakes were synthesized by a facile hydrothermal synthesis and a post-annealing treatment. As an anode for lithium-ion batteries, it exhibits high capacity, excellent cyclability and ultrahigh rate performance. A reversible capacity of 1138 mAh g −1 at 1 A g −1 was obtained after 500 cycles. After cycled at current densities from 0.2 to 25.6 A g −1 , the reversible capacity can recover to 1089 mAh g −1 at 0.2 A g −1 . It has been demonstrated that the wrinkled-paper-like ZnCo 2 O 4 nanoflakes are promising for application as future energy storage units. [ABSTRACT FROM AUTHOR]

In this paper, we synthesize a new type of Ni-Co selenides (Ni 0.34 Co 0.66 Se 2 nanorod) on carbon fiber paper (CFP) as flexible electrode for supercapacitor. Comparing with NiCo 2 O 4 and NiCo 2 S 4 , the Ni 0.34 Co 0.66 Se 2 exhibits superior capacitive performance including high areal capacitance (2.61 F cm −2 at 4 mA cm −2 ), good rate capability (75% of retention from 4 to 20 mA cm −2 ) and excellent long-term cycling stability (only 7.4% of loss after 6000 cycles). When assembled into a symmetric supercapacitor, the as-obtained, Ni 0.34 Co 0.66 Se 2 based device possesses a volumetric capacitance of 14.55 F cm −3 at 1 mA cm −2 , and a volumetric energy density of 0.47 mWh cm −3 at 10 mA cm −2 , which are superior to most of the symmetric supercapacitors reported previously. Then we explore the energy storage mechanism of Ni 0.34 Co 0.66 Se 2 by monitoring the changes in component, morphology, electroactive surface area (ESA) and electron transport characteristics. It is found that the Ni 0.34 Co 0.66 Se 2 species suffer from serious Se loss and transform into Ni x Co 1-x O gradully during charge/discharge cycles, but the ESA increases significantly in this process. In addition, the Ni 0.34 Co 0.66 Se 2 electrode possesses lower internal resistance, indicating its good electron transfer properties. Both these factors will compensate the performance degradation from Se loss, resulted in better rate capability and cycling stability for Ni 0.34 Co 0.66 Se 2 electrode. Therefore, it is believed that the proposed 3D Ni 0.34 Co 0.66 Se 2 nanorod array modified CFP with optimizational component and structual design opens a new horizen in the development of high-performance flexible supercapacitor electrode with new charge storage mechanism. [ABSTRACT FROM AUTHOR]

Designing highly efficient electrocatalysts for oxygen evolution reaction is important to meet the requirement of various renewable energy storage and conversion devices. Generally, the performance of OER catalysts can be significantly improved by synergistic action of the underlying conductive substrate. In this work, a commercial graphite paper was used as a facile substrate with catalytic activity. Graphite paper produced 10 mA cm −2 at an overpotential of 447 mV with a Tafel slope of 62 mV dec −1 . By depositing NiFe hydroxide or Mn oxide film onto the graphite paper, the electrode presented a superior activity for water oxidation, which was believed to be synergistically contributed by their available electrochemically active sites associated with the deposited film and the active substrate. High activities were also accompanied by remarkable durability at large current density levels. Our results illustrated a guideline to the design of inexpensive and highly active composite electrode for water oxidation. [ABSTRACT FROM AUTHOR]

In order to develop a low cost, sustainable, and eco-friendly energy storage device, we demonstrated an all solid state symmetric flexible supercapacitor based on the office waste paper fibers-reduced graphene oxide-manganese dioxide (PF-RGO-MnO 2 ) which acts as both the positive and negative electrodes. With the assistance of facile solution phase assembly and vacuum filtration method, the flexible PF-RGO-MnO 2 electrodes with high physical flexibility and excellent mechanical strength were fabricated directly without any binder agents. Furthermore, owing to the advantages of the lager surface area and microfibers of the each single paper fiber, the PF-based hybrid flexible electrodes show high specific capacitance of 410 F g − 1 at 0.8 A g − 1 and retain 93% capacitance over 5000 cycles, indicating outstanding electrochemical performance. In addition, the assembled solid-state symmetric supercapacitors exhibit high energy density (19.6 Wh kg − 1 at 400 W kg − 1 ) and excellent cycling stability of 85.3% retention even after 2000 folding and bending cycles. These results propose a renewable way to turn “waste” into wealth, and provide a new method to fabricate the sustainable and freestanding paper-based supercapacitor for application in the flexible energy storage devices. [ABSTRACT FROM AUTHOR]

Graphene-based all-solid-state supercapacitors (ASSSCs) have received increasing attention. It’s a great challenge to fabricate high-performance flexible solid-state supercapacitors with high areal and volumetric energy storage capability, superior electron and ion conductivity, robust mechanical flexibility, as well as long term stability. Herein, we report a facile method to fabricate flexible ASSSCs based on densely-packed reduced graphene oxide (rGO)/polypyrrole nanoparticle (PPy NP) hybrid papers with a sandwich framework, which consists of well-separated and continuously-aligned rGO sheets. The incorporation of PPy NPs not only provides pseudocapacitance but also facilitates the infiltration of gel electrolyte. The assembled ASSSCs possess maximum areal and volumetric specific capacitances of 477 mF/cm 2 and 94.9 F/cm 3 at 0.5 mA/cm 2 . They also exhibit little capacitance deviation under different bending states, excellent cycling stability, small leakage current and low self-discharge characteristics. Additionally, the maximum areal and volumetric energy densities of 132.5 μWh/cm 2 and 26.4 mWh/cm 3 are achieved, which indicate that this hybrid paper is a promising candidate for high-performance flexible energy storage devices. [ABSTRACT FROM AUTHOR]

SnO 2 -graphene nanocomposites (SGNs) are synthesized by a facile hydrothermal method, and SGN paper as both the anode and current collector of lithium-ion battery has been investigated. The paper exhibits high capacity, good cyclability, lightweight and excellent flexibility. At 0.1 C rate (10 h per half cycle), the discharge capacity of SGN paper is 1195 mAh g −1 at 10th cycle and can maintain at 1094 mAh g −1 after 80 cycles. The paper based flexible cells also show high performance. It can be attributed to the synergistic effect. The present results indicate that SGN paper is one of good candidates for fabricating flexible lithium-ion batteries. [ABSTRACT FROM AUTHOR]

To increase the conductivity and overcome the solubility and agglomeration of polyoxometalate (POMs), herein, paper ball-like graphene (PBG, 100 mg) anchoring different amount (200 mg, 600 mg, 900 mg) of H 3 PMo 12 O 40 (PMo 12) nanocomposites (donated as PBG@PMo 12 (n) (n = 1, 2, 3, respectively)) were successfully fabricated, in which the PBG can not only improve conductivity of PMo 12 but also effectively prevent PMo 12 aggregation. Moreover, the PBG and PBG@PMo 12 (n) nanocomposites were characterized by PXRD, FT-IR, SEM and TEM. As a consequence, when the PBG@PMo 12 (n) (n = 1, 2, 3) nanocomposites were used as the anode materials for lithium-ion batteries (LIBs), PBG@PMo 12 (n) (n = 1, 2, 3) exhibit superior behavior of energy storage, especially, PBG@PMo 12 (2) exhibits a high reversible capacity of 583.2 mA h g−1 up to a cycle life of 100 cycles, being better than those of matrix and others. The results indicate that the PBG can provide a favored contact between POMs and electrolyte, resulting in the enhanced capacity. [Display omitted] • Paper ball-like graphene (PBG) anchoring different amount of H 3 PMo 12 O 40 were successfully fabricated. • In the PBG@PMo 12 (n), the PBG can not only improve conductivity of PMo 12 , but also effectively prevent PMo 12 aggregation. • PBG@PMo 12 (2) exhibits a high reversible capacity, being far greater than that of PMo 12. [ABSTRACT FROM AUTHOR]

We propose a low cost and simple method to prepare a paper-based supercapacitor in this study. Multi-walled carbon nanotubes (MWCNTs) were dispersed with a pectin solution under an ultrasonic homogenizer. Carbon nanotube suspension was prepared using a centrifuge to eliminate impurities. The dispersed MWCNTs suspension was dropped and dried onto the shallow surface of commercial copy paper. A paper-based conductive paper was formed as the electrodes. The electrical conductivity and dispersed morphology of the paper-based conductive paper were examined by four probes, atomic force microscope (AFM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The solid-state electrolyte was prepared by casting a solution of phosphoric acid and polyvinyl alcohol onto a glass plate. The paper-based supercapacitor was constructed with one solid-state electrolyte inserted between two electrodes, which were assembled into a sandwich structure by hot press. The specific capacitance and cycle-life stability of the paper-based supercapacitor was investigated by cyclic voltammetry analysis. [ABSTRACT FROM AUTHOR]

Novel and flexible Mn 3 O 4 nanosheets/reduced graphene oxide nanosheets (Mn 3 O 4 NSs/rGO NSs) paper-like electrodes have been developed by a feasible method. The rGO works as a flexible substrate and an electron conductor. The synergetic effect of interconnected nanosheet structure can effectively depress self-agglomeration of rGO, which displays eminent conductivity. Moreover, the crumpled surface with more active sites are more convenient for the ion and electron insertion/desertion in the reversible reactions. So flexible Mn 3 O 4 NSs/rGO NSs electrode exhibited a high specific capacitance of 409 F g −1 at a current density of 0.5 A g −1 , superior cycling stability of 92% after 3000 charge-discharge cycles. More importantly, the composite material was first applied in 3D printing and screen printing of micro-patterns because of the desirable processability. It is anticipated that the high-performance Mn 3 O 4 NSs/rGO NSs composites are a promising electrode material in printable energy storage and wearable electronic equipment. [ABSTRACT FROM AUTHOR]

Cobalt-based nanomaterials have received considerable attention in electric energy-storage devices due to their outstanding electrochemical characteristics. However, multiple time- and energy-consuming steps and complex reduction processes for producing cobalt and cobalt oxide nanostructures are disrupting their substantive commercialization. Here, we propose a facile, ultra-fast, and versatile method for the fabrication of cobalt and cobalt oxide nanostructures using an intense pulsed white light (IPWL) photothermal reduction technique. The mechanism of the IPWL photothermal reduction of cobalt and cobalt oxide is firstly studied by measuring the in-situ temperature of the Co(NO 3 ) 2 -coated carbon fiber paper (CFP) substrate during IPWL irradiation and analyzing the crystal structures of the IPWL-irradiated samples. Cobalt nanoflakes and cobalt oxide nanoparticles are synthesized on the surface of the CFP substrate by irradiating IPWL for 10 ms at ambient temperature and pressure with various energy densities from 10 to 30 J cm −2 . The Co 3 O 4 nanoparticle/CFP and Co nanoflake/CFP samples are further utilized as an electrode, and each electrode exhibits high specific capacity of 29 and 73 mA h g −1 , respectively, at a current density of 1 A g −1 . Since this novel photothermal reduction technique is applicable to other transition metals and metal oxides, it is a promising method for not only energy storage systems, but also for energy generation applications, filters, sensors, and catalysis systems. [ABSTRACT FROM AUTHOR]

Layered α-Co(OH) 2 nanosheets have been widely investigated as one of the promising supercapacitor materials owing to its high theoretical specific capacitance (3,460 F g −1 ). However, their poor electrical conductivity, poor stability, and unclear charge storage mechanism limit their practical use in energy storage systems. To address the first two drawbacks of layered Co(OH) 2 , conductive silver nanoparticles (AgNPs) with a finely tuned loading content were for the first time incorporated to the layered Co(OH) 2 structure coated on a flexible reduced graphene oxide (rGO)paper substrate. In situ electrochemical X-ray absorption spectroscopy (XAS) was also used to investigate the charge storage mechanism of AgNPs/Co(OH) 2 electrode. It was found that the incorporation of AgNPs with an average diameter of <10 nm can significantly enhance the charge storage capacity of Co(OH) 2 due to high electrical conductivity leading to fast charge transport. The charge storage mechanism of the Ag-doped α - Co(OH) 2 energy storage cell is based on an intercalation/de-intercalation process (a battery-like behavior) and a physical adsorption of solvated ions (a supercapacitor-like behavior). The incorporation of AgNPs to the layered Co(OH) 2 nanosheets in this work can overcome the current drawbacks of the Co(OH) 2 , which may lead to practical use as a hybrid energy storage device. [ABSTRACT FROM AUTHOR]