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• A hierarchical MnCo 2 O 4 @MnWO 4 core-shell nanoarrays on NF is obtained. • 2. Nanoarrays and synergy provide high capacitance retention and rate performance. • 3. Unique structure and large specific surface area avail the diffusion of electron/ion. • 4. The ASC device shows an energy density of 36.46 Wh kg−1 at 750 W kg−1. Supercapacitors (SCs) are generally perceived as competitive possibilities for portable electronic products due to their exceptionally high power density and extended operational lifespan. Nevertheless, the relatively low energy density remains a crucial obstacle to its widespread application. A hierarchical MnCo 2 O 4 @MnWO 4 core-shell nanoarrays on nickel foam (NF) was designed and synthesized by utilizing the MnCo 2 O 4 nanosheet array as the backbone and the MnWO 4 nanosheet array as the shell via hydrothermal procedure and calcination. The MnCo 2 O 4 @MnWO 4 /NF electrode achieves 1428.5 F g−1 at 1 A g−1 with 97.8 % of its pristine capacity after 4000 cycles. The superior energy storage characteristic is a result of several factors, including the binder-free integrated electrode design, the synergistic effect between MnCo 2 O 4 and MnWO 4 , and abundant active sites. The assembled asymmetric supercapacitor (ASC) has an energy density of 36.46 Wh kg−1 at 750 W kg−1, and 85.4 % capacity reserved after 5000 cycles. [Display omitted] [ABSTRACT FROM AUTHOR]

The present work includes fabrication of a binary and ternary and composites of reduced graphene oxide (RGO), Polyaniline (Pani), and cobalt Prussian blue analog (Co-PA) for high performance supercapacitor. The materials were characterized using XRD, SEM, FT-IR, and BET techniques. The results confirm the formation of the desired nanocomposites. The electrochemical properties were evaluated in three electrode configuration using CV, CCD and EIS methods. The ternary composite of RGO@Pani@Co-PA showed better electrochemical properties than that obtained from the binary composites as well as their constituent components. The ternary-based sample had a specific capacitance of 490 Fg-1 at a current density of 1 A g-1 and a minimal capacitance loss of 93.9% after 3000 electric cycles. The ternary composites' remarkable electrochemical performance has been attributed to their well-thought-out, distinctive architecture, which offers a substantial surface area and promotes synergistic effects among the other ingredients. The ternary RGO@Pani@Co-PA composite was used as the anode electrode (positive) and activated carbon as the cathode (negative) materials in the assembly of the asymmetric supercapacitor (ASC) device. Over a wide potential window of 2 V, the fabricated ASC had a remarkable specific energy of 58.9 Wh kg-1 at a specific power of 9210 W kg-1 and 88.5% device capacitance stability after 5000 cycles of charge/discharge. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of the oxygen evolution reaction (OER) refers to the major contributor to the energy losses in electrowinning of metals. Improving the stability in the long term and activity of the electrocatalyst for OER take on a critical significance in reducing the energy consumption. An efficient and stable OER electrode (named as Ti/SMST/IrO 2 electrode) was prepared in this study by supporting IrO 2 nanoparticles on the surface of the submicrometer-sized TiO 2 (SMST) interlayer. The obtained results indicated that the IrO 2 nanoparticles approximately 14 nm in size were supported onto the submicrometer-sized TiO 2 particles' surface and exhibited a cactus-like morphology. The Ti/SMST/IrO 2 electrode with the SMST interlayer prepared at 450 °C exhibited the highest electrocatalytic activity in terms of OER for its largest active surface area. This electrode showed an overpotential of 350 mV at a current density of 50 mA cm−2 and displayed a remarkable electrochemical stability of 443 h at a high current density of 2 A cm−2 in H 2 SO 4 solution without significant change in OER activity. The prepared Ti/SMST/IrO 2 electrode with high electrocatalytic performance is considered one of the promising electrodes for OER. [ABSTRACT FROM AUTHOR]

This paper conducts a one-dimensional theoretical study on the electrochemical phenomenon in the dual-layer cathode electrode of polymer electrolyte fuel cells (PEFCs) with varying sub-layer thicknesses, and further extends the analysis to a triple-layer configuration. We obtain the explicit solution for a general dual-layer configuration with different layer thicknesses. Distributions of the key quantities such as the local reaction current and electrolyte overpotential are exhibited at different ratios of the ionic conductivities, electrochemical kinetics, and layer thicknesses. Based on the dual-layer approach, we further derive the explicit solutions for a triple-layer electrode. Sub-layer performances are plotted and compared. The results indicate that the layer adjacent to the electrolyte membrane may contribute a major part of the electrode faradic current production. The theoretical analysis presented in this paper can be applied to assist electrode development through complicated multi-layer configuration for cost-effective high performance electrodes. © 2010 Elsevier Ltd.

• The mesoporous nanoneedle-like NiFe 2 O 4 have been proposed for CDI;. • The desalting capacity realizes the linear correlation with the mass of NFO electrode;. • The electrosorption mechanism of NFO has been explored. In this work, the nanoneedle-like NiFe 2 O 4 (NFO) has been prepared by a template method and post annealing process for capacitive deionization (CDI) with enhanced performance. Owing to the unique structure, the nanoneedle-like NFO provides large accessible surface area, which benefits to offer abundant electroactive sites for electrosorption. Meanwhile, the salty ions diffusion and electron exchange are promoted by needle-like structure. Further, it is found that the NFO annealed at 450 °C (NFO-450) demonstrate the high crystallinity, rich mesopores and exceptional electrochemical properties. As electrode for CDI, the NFO-450 has manifested the high desalting capacity of 1.62 mmol/g when the effective loading mass of both electrodes is 23.6 mg. Interestingly, the desalting capacity realizes the linear correlation with the mass of NFO electrode ranging from 23.6 to 45.8 mg. The mechanism analysis stands out that the Na+ are captured by NFO, accompanied by the reduction of Ni3+ to Ni2+ in the 1st cycle. Afterwards, the Na+ can be electrostatically removed by the NFO//AC system. [Display omitted] [ABSTRACT FROM AUTHOR]

An electrochemical exfoliation-deposition strategy is provided to fabricate the MnO 2 -based electrode. After the efficient exfoliation in MnSO 4 electrolyte, the stacked graphite expands into open structure, with vertical graphene sheets strongly bonded on the surface. This unique architecture not only provides sufficient surface areas for the anchoring of oxygen vacancy-enriched MnO 2 , but also ensures transportation pathways for the charge transfer and electrolyte ions diffusion. Thus, the resultant electrode exhibits an areal specific capacitance of 447.5 mF cm−2 at 0.5 mA cm−2 and promising cycling stability. It outperforms the analogues exfoliated in another Mn-based electrolyte because of the anion effect. In situ Raman spectra are taken to reveal the structural evolutions of the resultant electrode coupled with Na+ ions insertion-extraction behaviors in the redox pseudocapacitive process. An electrochemical exfoliation-deposition strategy is provided to fabricate graphene-graphite architecture deposited with MnO 2. This unique architecture provides sufficient surface areas for anchoring oxygen vacancy-enriched MnO 2 and ensures transportation pathways for charge transfer and electrolyte ions diffusion. The charge storage of MnO 2 is realized by the redox process of Mn4+/3+ coupled with Na+ ion insertion and extraction in the tunnels. [Display omitted] [ABSTRACT FROM AUTHOR]

• Individualized customization of electrodes in VRFBs is realized by electrospinning. • Both positive and negative electrode reaction kinetics have been improved. • Dynamical difference of the electrode reactions in VRFBs has been reduced. • Asymmetric VRFB shows superior performance. There are significant differences in the cathodic and anodic kinetics of vanadium redox flow batteries (VRFBs), thus the use of a single composition and structure of electrode materials is unbefitting according to the barrel principle. Herein, W and Sb based electrocatalysts are evenly embedded into the electrospun carbon nanofibers (ECNFs), and the active functional groups and surface defects of the W-ECNFs and Sb-ECNFs electrodes are increased effectively, which resulted in a significant improvement in their hydrophilicity, specific surface area and electrocatalytic activity towards the VO 2 +/VO2+ and V3+/V2+redox reactions. The electrode reaction rate constant k and diffusion coefficient D of the positive and negative reactions on W-ECNFs and Sb-ECNFs are more similar and closely matched, which is more conducive to the effective improvement of battery performance. As a results, the asymmetric battery with W-ECNFs and Sb-ECNFs as positive and negative electrode shows the highest energy efficiency of 81.33% at 200 mA/cm2, higher than that of the VRFBs with pristine ECNFs as both two electrodes (75.66%) or that only optimizing one electrode (79.76% and 78.15%). The excellent battery performance further verifies the feasibility of constructing asymmetric batteries according to the difference of the positive and negative reaction kinetics in VRFBs. [Display omitted] The gap between anode and cathode reaction kinetics is closed by individualized customization of the anode and cathode electrode materials in a VRFB, and the battery performance is improved more significantly due to the asymmetric structure design. [ABSTRACT FROM AUTHOR]

• Synthesis of NiO/Mn 2 O 3 nano-pyramids via composite hydroxide-mediated approach. • Enhanced ion transformation rate between electrolyte and electrode. • High specific capacitance of 1730.5 F g−1 at a low current density of 1.5 A g−1. • Excellent cyclic stability is perceived from NiO/Mn 2 O 3 nanocomposites. Herein, we report the synthesis of bimetallic oxide (NiO/Mn 2 O 3) as an efficient positive electrode for supercapacitor application prepared by a facile one-step composite hydroxide-mediated approach. Exceptional electrochemical performance has been achieved by optimizing the composition, structure, and morphology. Simple cubic crystal structure with bipyramid surface morphology provided a large specific surface area and more active sites for rapid transfer of ions between electrolyte and electrode. The electrochemical performance of prepared electrodes was examined in a three-electrode system, where nickel foam was used as a conductive support. From the electrochemical measurements, the NiO-50 % Mn 2 O 3 exhibited the highest specific capacitance of 1730.5 F g−1 at a current density of 1.5 A g−1 in a 3 M aqueous KOH electrolyte. The optimized electrode showed long-term cycling stability of 4000 charge-discharge cycles at a high retention rate of 97.5 % at 10 A g−1, which supports the excellent performance of the electrode and robust stability. Hence, owing to its unique bipyramid-like morphology, outstanding performance, and easy one-step synthesis process, NiO/Mn 2 O 3 bimetallic oxide can be considered an excellent candidate for supercapacitor electrodes. This method provides an efficient hybridization methodology for the design of high-performance electrode materials for advanced energy storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

A metal organic framework with dual metal centers (Ni-Co-MOF) was directly grown on graphene oxide sheets (Ni-Co-MOF/GO) via a one-pot solvothermal reaction and used as a hybrid supercapacitor electrode. Synthesis of the composite employs water as an environmentally friendly solvent and 2-methylimidazole as an inexpensive organic ligand. Ni-Co-MOF/GO with a 3D structure possesses features that provide a large specific surface area, a stable interface between the electrolyte and electrodes, and better charge transfer path. The synergistic effects of mixing cobalt and nickel and the electrochemical behaviors of the graphene oxide content on the mixed metal organic framework were investigated. Ni-Co-MOF/GO 2 (amount of graphene oxide, 0.2 g) showed the highest energy storage performance. At a current density of 1 A g−1, the maximum specific capacitance was 447.2 F g−1, with excellent rate capability. Evaluation result of the cycle characteristics of Ni-Co-MOF/GO 2 showed outstanding life stability of 99.6% after 300 cycles. Based on the performance of the Ni-Co-MOF/GO electrode, this material is expected to pave the way for the development of promising materials, which hold good electrochemical properties for supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract Nanostructured carbons with a number of redox-active sites play a key role as active electrode materials for supercapacitors and rechargeable batteries, owing to their pseudocapacitive charge storage behaviors. Nevertheless, there is currently no method to characterize the level of contribution of pseudocapacitance in overall capacitance values, hindering technological and scientific advancement of pseudocapacitive electrode materials. In this study, we can observe the voltage-dependent pseudocapacitive behaviors of heteroatom-enriched nanoporous carbons, which can be detected through a simple comparison of electrochemically obtained results in both aqueous and organic electrolyte systems. It is also confirmed that the voltage-dependent pseudocapacitive behaviors are so fast and stable that the heteroatom-enriched nanoporous carbons based on the voltage-dependent pseudocapacitive behaviors can deliver high specific energy and power as cathodes when they are assembled with a proper counterpart anode. [ABSTRACT FROM AUTHOR]

Abstract We present a simple and effective alternative which optimizes electrodes based on low-cost carbons for high-performance supercapacitors. The combination with reduced graphene oxide (rGO) greatly improves the operation of microporous carbons easily produced by one-pot activation of grape seeds. The use of composite electrodes with rGO lowers the supercapacitor resistance and enables a much higher rate capability. The mixture of rGO flakes and particles of a highly porous carbon obtained by KOH activation allows retaining the high capacitance of 260 F g−1 of the standard electrodes at 1 mA cm−2 in aqueous H 2 SO 4 whereas the value at 200 mA cm−2 is increased by around 2.4 times. Consequently, at high current density, the capacitor assembled with these composites stores eight times more energy and the power density is multiplied by four. The synergy between rGO and an ultramicroporous carbon produced by CO 2 -activation results extremely profitable, the cell assembled with composite electrodes reaching three times more energy and power at 200 mA cm−2 than the best performance of the standard counterpart. More importantly, the higher density of the composite electrodes leads to a capacitance of around 200 F cm−3 which translates into a remarkable improvement in the supercapacitor operation normalized to volume. Graphical abstract Image 1 Highlights • Optimization of electrodes based on low-cost carbons for high-power supercapacitors. • The combination with rGO greatly improves the operation of microporous carbons in SC. • Composite electrodes reach capacitance as high as 260 F g−1 and 200 F cm−3. • Cells with composite electrodes store 8 times more energy with a power 4 times higher. [ABSTRACT FROM AUTHOR]

In this research, the flow behavior through a commercial electrode used in Redox Flow Batteries (RFB) was characterized by means of Planar Laser Induced Fluoresce imaging (PLIF) for different cell configurations, without channels or with channels machined either in the back plate or in the electrode. Measurements of the pressure drop were obtained for each case, and the evolution of the electrode soaking process was quantified defining an electrode surface wetting rate. Using the pressure drop measurements, equivalent Darcy and intrinsic permeability coefficients were calculated for the different configurations. It was observed that the tight fitting of the electrode within its housing appears to be crucial for an adequate distribution of the electrolyte within the porous media. In general, when channels are available, the electrolyte tends to circulate along them, without crossing through the electrode felt, and lower pressure losses are accompanied by lower wetting rates. The flow field with serpentine channels in the back plate could be considered the most suitable configuration in terms of energy consumption, nearly 87% less than in a case without any channels, but this same percentage of electrolyte will exit the cell without traversing the electrode, and thus not contributing to the electrochemical reactions. [ABSTRACT FROM AUTHOR]

Abstract Ni-rich layered oxide (Ni-rich NCM) is a promising advanced cathode material for lithium-ion batteries (LIBs) because of its high specific capacity. However, the high Ni content in the layered structures is associated with poor surface stability, which in turn accelerates the capacity fading of the cell. To improve the interfacial stability of Ni-rich NCM cathode material, we propose poly(thiophene)-based artificial cathode-electrolyte interphase (CEI)-immobilized Ni-rich NCM cathode material, synthesized using a simple and convenient one-step spin-coating process. At room-temperature cycling, cells with thiophene-modified NCM811 cathodes exhibit improved cycling retention (>91.3%), compared those with bare NCM811 (84.2%). The effectiveness of the artificial CEI layer is evident during high-temperature cycling: cells with 36 kDa-NCM811 exhibit a specific capacity retention of 89.4%, whereas those with bare NCM811 exhibit a drastic decrease in the cycling retention capacity (55.1%) at 55 °C. XPS analyses reveal that the improved electrochemical performance of cells with cycled NCM811 cathodes is due to the surface stability of the cathode; the decomposed adducts in the recovered 36 kDa-NCM811 cathodes are less, whereas they are present in considerable amounts in the cycled NCM811 cathode. In addition, it is confirmed that the molecular weight of the polymer used for the artificial CEI-layer formation significantly affects the electrochemical performance of the cell; polymers with low molecular weights are preferred because P3HTs with low molecular weight have high crystallinity with a hard phase, particularly at high temperature, due to their low T g. Highlights • Thiophene-initiated artificial CEI layer is immobilized on Ni-rich NCM cathode. • Artificial CEI layer effectively suppresses electrolyte decomposition on electrode. • NCM modified by artificial CEI layer gives improved high temperature cycling. [ABSTRACT FROM AUTHOR]

Low energy density of the supercapacitors is considered as a roadblock for its application in or as a primary power source. While, utilization of high energy density battery-type electrode materials in an asymmetrical configuration was expected to resolve this hurdle, however, its inferior rate performance and poor cycling stability hinder the overall device performance. Incomplete utilization of active material at elevated current density was identified as the root for poor rate performance. Herein, we developed a hierarchical NiS microspheres build by the self-assembly of hexagonal nanoplates via trimethylamine (TEA) assisted hydrothermal method. The optimized sample exhibited a superior specific capacitance of 606 C/g at 0.5 A/g. More interestingly, the electrode was able to retain 50% (302 C/g at 20 A/g) of its maximum capacity even when the current density was multiplied 40-fold relative to 18% (50 C/g at 20 A/g) shown by control sample prepared without TEA. Excellent rate performance of the electrode could be attributed to the increment in the electrolyte-accessible surface area by morphological modifications. Owing to its porous nature, optimized sample was able to retain 93% of its original capacity at the end of 2000 continuous cycles of charge-discharge. Furthermore, an asymmetric supercapacitor with NiS-C as the positive electrode and activated carbon as the negative electrode delivered a high energy density of 35.07 Wh/kg at a power density of 0.420 kW/kg within an operating voltage window of 1.5 V. [ABSTRACT FROM AUTHOR]

In this paper, flexible carbon nanofiber embedded with TiO 2 (CNF/TiO 2 ) was prepared by electrospinning technique, and used as negative electrode for vanadium redox flow battery (VRFB). CNF/TiO 2 composites were synthesized from solution consisting of Ti(OC 4 H 9 ) 4 as TiO 2 precursor and polyacrilonitrile (PAN) as carbon precursor. High-purity rutile TiO 2 can be dispersed evenly in CNF with the diameter of 100–200 nm. CNF/TiO 2 composites exhibited superior electrochemical activity towards V 2+ /V 3+ redox reaction compared with pristine CNF. The excellent energy storage performances of VRFB were achieved via using CNF/TiO 2 as negative electrode, with larger capacity and efficiency. At a current density of 90 mA cm −2 , the discharge capacity of the cell using CNF/TiO 2 electrode reached 84.0 mA h, 48.5 mA h higher than that of pristine cell. The energy efficiency of the cell based on CNF/TiO 2 increased by 8.7% compared with pristine cell. The excellent electrochemical performance of CNF/TiO 2 composite towards V 2+ /V 3+ redox reaction was attributed to the synergistic effect between carbon nanofiber networks with high conductivity and rutile TiO 2 with high electrocatalytic properties. [ABSTRACT FROM AUTHOR]

Neodymium oxide (Nd 2 O 3 ) nanoparticles were chemically embedded on a state-of-the art carbon felt (CF) by a precipitation method in non-aqueous solution. Different Nd 2 O 3 loadings were chosen and the obtained electrocatalyst-loaded felts tested for application as electrode in all-vanadium redox flow batteries. Cyclic voltammetry (CV) studies confirmed that Nd 2 O 3 has a catalytic effect towards both redox couples, V 4+ /V 5+ at the positive and V 2+ /V 3+ at the negative side. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) demonstrated only minor particle agglomeration and high dispersion of the particles on the fibres. Charge/discharge profiles revealed an enhanced performance with higher discharge capacity and higher energy efficiency for the modified felts when compared to a thermally activated CF. For instance, after 50 consecutive charge/discharge cycles the energy efficiency of the Nd 2 O 3 modified carbon felt (Nd 2 O 3 -CF) was reduced only by 3% compared to a 12% irreversible loss observed for the thermally activated CF. After exchanging the electrolyte after 50 cycles, the felts retained their original performance indicating that less degradation occurred in the modified felts than in the industrial standard and that they maintained their oxygen-donating functionalities on the surface as compared to thermally activated CF. [ABSTRACT FROM AUTHOR]

A binder-free electrode of ultrafine MnO 2 nanowires grown on the carbon cloth (CC) were fabricated by simple hydrothermal method, exhibiting the interconnected network with weed-like morphological feature. The unique pore structure has a large interface surface area, and allows rapid electrolyte diffusion through its hollow/open framework and fast electron transfer though the carbon skeleton. As an electrode for supercapacitors, the ultrafine MnO 2 nanowires grown on the CC (ultrafine MnO 2 nanowires@CC) exhibit a high specific capacitance (1174.3 F g −1 at the moderate current density of 2 A g −1 ), excellent rate property (stabilize at 927 F g −1 as the current density increases to 40 A g −1 ), and good cycling stability (a negligible 0.1% decay in specific capacitances after 10,000 cycles). [ABSTRACT FROM AUTHOR]

The photovoltaic performance of the dye-sensitized solar cell is enhanced remarkably through using magnetic counter electrode. This kind of counter electrode catalyst is a core-shell structured paramagnetic carbon sphere using carbon as shell and paramagnetic Fe 3 O 4 as core. After analyzing the catalytic behaviors of carbon sphere, Fe 3 O 4 , and paramagnetic carbon sphere on nonmagnetic and magnetic substrates toward the cobalt complex redox couple, it is proved that the internal magnetic field is conducive to both charge transfer and the mass transport processes in the electrode/electrolyte interfaces. The dye-sensitized solar cell using the magnetic carbon sphere counter electrode on magnetic substrate yields a power conversion efficiency of 10.71%, much higher than those using magnetic carbon sphere counter electrode on conductive glass (8.74%), carbon sphere counter electrode on magnetic substrate (8.50%), and Fe 3 O 4 counter electrode on magnetic substrate (6.86%). [ABSTRACT FROM AUTHOR]

Graphene gel is an excellent material for capacitive deionization (CDI) because of its high specific surface area, three-dimensional structure and binder-free preparation. Current studies have been primarily focused on the design and synthesis of new graphene gel materials. However, there have been no studies comparing the desalination performance of graphene hydrogel (GH) and graphene aerogel (GA), the two primary CDI materials. In this work, GH and GA were synthesized and applied in CDI. A range of characterization methods were used to analyze the microstructure of the GA and GH electrode materials. The results showed that the electrosorption capacities of GH and GA were 49.34 and 45.88 mg g −1 , respectively, in sodium chloride solution with an initial concentration of 500 mg L −1 at 2.0 V. A water-enhanced function mechanism was proposed to explain the differences in desalination performance. [ABSTRACT FROM AUTHOR]

A zeolitic imidazolate framework (ZIF)/graphene composite was prepared by the solvothermal reaction using different concentrations of graphene oxide to investigate the effect of graphene addition on the electroactivity of the composite. Field emission scanning electron microscopy (FE-SEM), field emission transmission electron microscopy (FE-TEM), and X-ray diffraction (XRD) were conducted to determine the morphology and micro-structure of the composite. Electrochemical characterizations were measured using the CR2016 type coin cell test. Based on the electrochemical properties and structural characteristics of the composite, the roles and effects of graphene in ZIF/graphene composite were studied. The concentration of graphene oxide used during the synthesis process affect the initial specific capacity and cycle performance of the composite. [ABSTRACT FROM AUTHOR]

Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO 2 )) on metal oxide anodes (such as tin (IV) oxide (SnO 2 )) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO 2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO 2 overlayer on SnO 2 can have significant influence in the overall parameters of electrochemistry. It is revealed that TiO 2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g −1 even at high current density (5000 mA g −1 ). Surprisingly, it was further discovered that TiO 2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO 2 . The improvements in both ionic and electrical conductivity of TiO 2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO 2 @SnO 2 , which demonstrates that TiO 2 overlayer results in homogeneous and thinner interphase layer compared with SnO 2 NTs. [ABSTRACT FROM AUTHOR]

Aluminized zinc oxide (AZO) thin films with different thickness were deposited and their electrical and optical properties of the studied films were measured. The results of XRD patterns and SEM measurement images verified that the micromorphology of the films correlated with the thickness. Meanwhile, it was demonstrated that the AZO films with the thickness of about 657 nm showed excellent balance between the electrical properties and optical properties. The highest value of Φ TC is 12.14 × 10 −3 Ω −1 for the thin films with the thickness of 657 nm, which exhibited the lowest R s of 36.67 Ω/□ and an effective average transmittance of 92.2%. The NiO x and WO 3 thin films were fabricated on as-deposited AZO films, respectively. The investigations of electrochemical properties of NiO x and WO 3 thin films suggested that AZO films prepared in 3.5 h with the thickness of 657 nm demonstrated the optimal performance when they served as the transparent electrode. Furthermore, in-situ spectro-electrochemistry studies of electrochromic devices, using 657 nm AZO films as the outer electrode, presented a long-term durability, high coloration efficiency (46.64 cm 2 C −1 ) and bleaching efficiency (58.79 cm 2 C −1 ). [ABSTRACT FROM AUTHOR]

The growing amount of carbon dioxide (CO 2 ) emission in parallel with the increasing greenhouse effect put the utilization of carbon dioxide in the focus of scientific interest in the past decade. Photoelectrochemical (PEC) conversion of CO 2 to useful products is one of the promising possibilities towards reaching this goal. In this paper, we report on the PEC behavior of polyaniline (PANI)/SiC photoelectrodes with various PANI/SiC ratios, obtained by electrochemical polymerization. Electrochemical polymerization allowed for the precise control over the composition and morphology; and ensured that PANI was only deposited on the surface of the SiC nanoparticles. The nanocomposite samples were characterized by scanning and transmission electron microscopy and Raman spectroscopy. Linear sweep photovoltammetry measurements showed improved PEC properties of the nanocomposites compared to their pristine counterparts (i.e., SiC and PANI). The enhancement was rooted in the (i) higher electrochemically available surface area, (ii) decreased bandgap (2.9 eV vs. 3.1 eV), and the (iii) mediating effect of PANI in both H 2 evolution and CO 2 reduction. Long-term CO 2 photoelectrolysis measurements coupled with analytical techniques ( 1 H NMR and GC-BID) confirmed the formation of hydrogen, carbon monoxide, methanol, and ethanol proving the capability of the nanocomposite material to reduce CO 2 to useful products. We think that lessons learned from this study may contribute to the rational design of nanocomposite photoelectrodes with enhanced performance for solar fuel generation. [ABSTRACT FROM AUTHOR]

A novel polyprrole (PPy)-decorated hierarchical NiCo 2 O 4 nanoneedles was grown on highly conductive carbon fiber paper (CFP) for high performance asymmetric supercapacitor applications. The PPy-decorated hierarchical NiCo 2 O 4 nanoneedle on CFP (PPy-NiCo 2 O 4 @CPF) was grown by two steps. At first, NiCo 2 O 4 nanoneedle was grown by hydrothermal process and followed by the deposition of PPy through electrochemical method. The fabricated PPy-NiCo 2 O 4 @CPF electrode displayed the higher electrochemical performance. The specific capacitance was ∼910 F g-1 at a current density of 1 A g −1 and cyclic stability was ∼88% after 10,000 cycles. To explore real performance of the electrode, we have fabricated solid state asymmetric supercapacitor using PPy-NiCo 2 O 4 @CFP as positive and nitrogen doped reduced graphene oxide (N-rGO) as negative electrodes. The fabricated asymmetric device delivered a specific capacitance of 118.6 F g-1 at a current density of 1.0 A g −1 with a maximum energy density of 40.81 Wh Kg −1 (at a power density of 738.27 W Kg −1 ) and maximum power density of 3746.77 W Kg −1 (at an energy density of 13.53 Wh Kg −1 ). The impressive results suggest that flexible PPy-NiCo 2 O 4 @CFPs can be a promising electrode material for supercapacitor applications. [ABSTRACT FROM AUTHOR]

The spinel-type transition metal oxides play key role in realizing cost-effective energy storage systems by exhibiting outstanding electrochemical activity and stability. Free standing 3D hierarchical mesoporous ZnCo 2 O 4 microspheres are grown on nickel foam (NF) substrate using hydrothermal route followed by annealing treatment. 3D hierarchical mesoporous ZnCo 2 O 4 microspheres with high surface area and uniform mesoporous distribution exhibits high electrochemical performance. The ZnCo 2 O 4 /NF electrode material deliver superior specific capacitance of 1143 F g −1 at a current density of 1.25 A g −1 in aqueous 2 M KOH solution and exhibits long-term cycling stability with specific capacitance of 880 F g −1 after 6000 cycles at 12.5 A g −1 . Furthermore, ZnCo 2 O 4 /NF electrode maintains current density upto 105 A g −1 in 1 M KOH mixed with 0.5 M methanol when applied as electro-catalyst for methanol electro-oxidation. The high electrochemical performance is mainly attributed to faster ion/electron transfer and an enhanced electrochemical kinetics. The present simple, and cost-effective synthesis approach can open new era for large-scale applications of the novel materials for different electrochemical applications. [ABSTRACT FROM AUTHOR]

Surface-driven charge storage materials based on both electrochemical double layer (EDL) formation and pseudocapacitive behavior can deliver high energy and power capabilities with long-lasting cycling performance. On the other hand, the electrochemical performance is strongly dependent on the material properties, requiring sophisticated electrode design with a high active surface area and a large number of redox-active sites. In this study, hierarchically nanoporous pyropolymer nanofibers (HN-PNFs) were fabricated from electrospun polyacrylonitrile nanofibers by simple heating with KOH. The HN-PNFs have a hierarchically nanoporous structure and an exceptionally high specific surface area of 3,950.7 m 2 g −1 as well as numerous redox-active heteroatoms (C/O and C/N ratio of 10.6 and 16.8, respectively). These unique material properties of HN-PNFs resulted in high reversible Na-ion capacity of ∼292 mAh g −1 as well as rapid kinetics and stable cycling performance in the cathodic potential range (1-4.5 V vs. Na + /Na). Furthermore, energy storage devices based on HN-PNFs showed a remarkably high specific energy of ∼258 Wh kg −1 at ∼245 W kg −1 as well as a high specific power of ∼21,500 W kg −1 at ∼78 Wh kg −1 , with long and stable cycling behaviors over 2,000 cycles. [ABSTRACT FROM AUTHOR]

• A method that combines macroscopic detection performance with microscopic analysis of materials. • The aging behaviors at different cylindrical winding positions were revealed. • The effect of discharge depth (DoD) on the aging rate was studied. • Under the condition of discharge at the 2C rate, the capacity decay of LFP slows down. • The outer layer of the electrode of the cylindrical battery decays faster than that of the inner layer. Lithium iron phosphate (LFP) batteries are widely used in the electric vehicle due to the great chemical stability and cost advantages. Fluctuations in the environment and driving conditions lead to a deterioration in battery performance that is inevitable. In addition, due to the winding manufacturing characteristics of cylindrical battery electrodes, the uneven distribution of current and temperature accelerates the aging process. In this paper, the cross-comparison aging test of cylindrical LFP batteries is designed, in which three kinds of constant current and two different dynamic working conditions are used for accelerated aging test at high temperature. The aging behavior and mechanism are investigated quantitatively by combination of in-situ electrochemical test and ex-situ Post-Mortem methods. During the long-term cycle of the battery, external characteristic parameters such as capacity, internal resistance, and open circuit voltage are periodically checked up. Until the capacity retention falls below 80%, the batteries are disassembled to sample the electrodes at the specified positions from the jelly roll. The material morphology changes of electrodes are observed by scanning electron microscopy. The half-cell tests were produced to obtain material-level aging information based on performance tests. This multi-scale analytical method enables the detailed process of performance loss, which guides performance prediction and safety diagnostics. [ABSTRACT FROM AUTHOR]

V 2 O 5 nanostructures have been synthesized through an environmental friendly and simple solvent-free solid-state chemical reaction. By changing the calcination temperature in air, V 2 O 5 nanostructures with different morphologies, such as hierarchical nanosheets, nanosheets, and hierarchical nanobelts, have been obtained. Electrochemical testing results show that hierarchical V 2 O 5 nanobelts exhibit high specific discharge capacity and excellent cycle stability, which display high discharge specific capacities of 240 mA h g −1 at 1C, whereas high discharge specific capacities of 174 mA h g −1 at 8C. The delivered capacity at 1C can maintain 91% of its initial capacity (the 2nd cycle) after 100 cycles. The V 2 O 5 nanobelts show good electrochemical performance due to its special hierarchical structure that reduces the contact resistance between the ions and materials, adjust the volume change, and relieve the pressure of large deformation in the charging/discharging process. The hierarchical V 2 O 5 nanobelts display promising application prospects as an excellent cathode material for lithium ion batteries. [ABSTRACT FROM AUTHOR]

A porous carbon monolith with a well-defined internal nanostructure consisting of highly redox-active materials has potential as an electrode in energy storage applications. In this study, 3D interconnected pyroprotein macrostructures (3D-IPMs) were fabricated from silk proteins using a simple templated sol-gel method and subsequently heated with potassium hydroxide. The resulting 3D-IPMs, which were further optimized, had high nitrogen concentrations (C/N ratio: 11.4), good electrical conductivities of ∼2.8 S cm −1 , and well-developed pore structures. The 3D-IPMs showed reversible storage capacities of ∼680 mA h g −1 at 0.1 A g −1 via a pseudocapacitive Li ion storage mechanism in the anodic potential range. Even when a 300-fold larger current rate was used, a reversible capacity of ∼230 mA h g −1 was maintained. In addition, the 3D-IPMs exhibited remarkable stability over the course of 1,000 cycles. The practicability of 3D-IPM-based energy storage devices was demonstrated by assembling full cells with a well-known cathode material. The full cell devices delivered a specific energy of 142.7 W h kg −1 at 190 W kg −1 and specific power of 23,850 W kg −1 at 48.1 W h kg −1 . In addition, their performance remained stable across many cycles. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage devices (EESDs) are critical technologies in modern economy, covering numerous fields such as portable electronics, electric vehicles, etc. The expanding market of EESDs demands for extra requirements such as safety, environmental friendliness and low cost, in addition to increasingly enhanced electrochemical properties. Natural proteins are abundant, versatile bio-macromolecules involving tremendous amount of amino acids/functional groups/heteroatoms, which greatly benefit sustainable technologies for advancing performances of EESDs. Recent years, significant research on utilizing natural proteins including plant/animal proteins to fabricate active materials for enhancing performance of EESDs has been well reported. Therefore, it is important to comprehensively summarize the progress and achievements, analyze the advantages/challenges, and predict the prospective for future protein-based strategies toward high-performance EESDs, which are the contents of this review. The protein-derived active materials include activated carbons, silicon, sulfur, metal alloys, transitional metal compounds, and nonprecious metal catalysts. The resulting EESDs are associated with Li-/Na-/K-ion batteries, metal–air batteries, and redox flow batteries, as well as supercapacitors. The contributions of proteins to stabilizing/protecting electrodes, and thus enhancing performance of EESDs are specifically emphasized. Furthermore, studies on genetical engineering of proteins for directing self-assembly of active material nanoparticles are introduced. [ABSTRACT FROM AUTHOR]

• The same polymer precursor of polyacrylonitrile/polysulfone is used to prepare carbon nanofiber and porous carbon. • Polysulfone can be as a sacrificial polymer to prepare carbon nanofiber with a large specific surface area. • Both carbon nanofiber and porous carbon electrodes show excellent electrochemical performances. • The carbon nanofiber electrode has a higher specific capacitance of ∼ 360 f g−1 than the PC electrode ∼ 290 f g−1 at 10 mV s−1. Currently, the supercapacitor attracts much attention because of its long cycling life, fast charge-discharge, high power density, and excellent security. Carbon-based active materials have already become promising electrode materials for supercapacitors, which determine the performance of supercapacitors. Compared to other carbon-based active materials, carbon nanofiber (CNF) and porous carbon (PC) have many advantages of low cost, easy manufacture, good conductivity, and stability. However, it is still a challenge to prepare CNF and PC electrodes used for supercapacitors with excellent physical-chemical properties through simple strategies. Herein, we innovatively use the same precursor, i. e. polyacrylonitrile/polysulfone blend polymer to prepare CNF and PC through one-step carbonization. The morphologies, chemical elements, graphitization extents, and porosity textures of as-prepared carbon materials are analyzed by Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD)/Raman, and N 2 physisorption, respectively. Both CNF and PC have large specific surface areas, hierarchical micro-meso pores, and perfect graphitization extents, which show excellent electrochemical performances when they are used as electrodes in supercapacitors. By contrast, the CNF electrode has a higher specific capacitance of ∼ 360 F g−1 than the PC electrode ∼ 290 F g−1 at 10 mV s−1. The difference in results may stem from the larger surface area, interconnected fiber-fiber structure, and nanoscale structure within CNF. [Display omitted] [ABSTRACT FROM AUTHOR]

In this article we report a facile method to create a polyaniline (PANI) nanorod/carbon nanoparticle (CNP) composite structure that is suitable for supercapacitor use. A network of CNPs was conveniently produced on the surface of a nickel foam by collecting candle soot above a burning candle. The PANI nanorods were then electrochemically deposited on the CNP network, forming a star-like interconnected 3D structure. As a comparison, MnO 2 particles were also deposited on the CNP network to produce a broccoli-like structure. The electrochemical properties of these two composites were examined using cyclic voltammetry, cyclic charge-discharge, and electrochemical impedance spectroscopy. The two electrodes exhibited different electrochemical behaviors: high capacitance at low current densities and marked deterioration at high ones for CNPs/PANI and relatively low but stable capacitance for CNPs/MnO 2 . The reasons for this distinction were discussed based on the structures and material properties of the electrodes. [ABSTRACT FROM AUTHOR]

The quest to increase the energy density and improve the cycle life performance of lithium ion batteries (LIBs) and beyond has led to the development of various suitable and alternative materials for energy storage and conversion. The morphology and electrode architecture in advanced battery materials have been re-designed into nanofibers and composite nanofibers. Nanofiber-based separators and electrodes have demonstrated to improve the energy density and cycling performance of LIBs. The improvement in the structure and morphology of nanofibers in LIBs such as LiSi and LiSn, have once again ignited the interest in these Li:M alloy anodes as alternative anode and cathode materials. The major challenges that confront this new frontier have the lack of scalable method among the various techniques and designing nanofibers with good structure and morphology that could prevent dendrite penetrations. However, there seems to be a solution in sight with the advent of mass production techniques such as electrospinning and Forcespinning ® that have recently been developed. In this paper, the use of nanofibers and composite nanofibers as electrode and separator materials for lithium ion, Li-O 2 and Li-S batteries is reviewed. The discussion focuses on the performance characteristics of these nanostructured electrode and separator materials and methods used to improve their performances. [ABSTRACT FROM AUTHOR]

This work reports the interfacial properties of nanostructured MnSn 2 as anode material for Li-ion batteries in order to explain ageing phenomena. The impedance measurements show variations of the solid electrolyte interphase (SEI) resistance during the first cycle that are interpreted from changes in thickness and/or porosity of the SEI film. These changes are mainly due to the degradation of the electrolyte at the beginning of the first discharge and to the de-alloying reaction of Li 7 Sn 2 operating during the first part of the charge that causes strong volume variations. However, a rather stable SEI was obtained during the reformation of MnSn 2 in the second part of the charge, which is peculiar to this compound. Finally, capacity fading is related to the continuous growth of the SEI during cycling. [ABSTRACT FROM AUTHOR]