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Amorphous films deposited by pulsed laser deposition from a crystalline Li 2 PO 2 N target in a N 2 ambient atmosphere (LiPON-PLD) have been examined as an approach to reduce the charge-transfer resistance at the electrode-solid electrolyte interface. Despite the relatively low ionic conductivity of ca. 1.5 × 10 −8 S cm −1 at 25 °C, the amorphous LiPON-PLD films deposited between a LiMn 1.485 Ni 0.45 Cr 0.05 O 4 (LNM) cathode and LiPON electrolyte resulted in sharply improved electrochemical performance in terms of charge-transfer resistance and CV profiles. Cells without a LiPON-PLD film had a charge-transfer resistance of 4470 Ω-cm 2 compared to 760 and 960 Ω-cm 2 for the sample with 17 nm and 31 nm thick LiPON-PLD films, respectively. The LiPON-PLD amorphous films show no evidence of the continuous planar P N P N- backbone characteristic of the crystalline target material, but compared with LiPON prepared from radio frequency magnetron sputtering with Li 3 PO 4 in a N 2 atmosphere, the LiPON-PLD films were composed of a higher amount of triply coordinated P − N < P P with relatively lower contributions of P N P. [ABSTRACT FROM AUTHOR]

A novel binder-free reduced graphene oxide/silicon (RGO/Si) composite anode has been fabricated by a facile doctor-blade coating method. The relatively low C/O ratio plays an important role for the fabrication of the bind-free multilayered RGO/Si electrode with silicon nanoparticles encapsulating among the RGO sheet layers. The RGO provides the electron transport pathway and prevents the electrode fracture caused by the volume changes of active silicon particles during cycling. The RGO/Si composite anode with a silicon content of 66.7% delivers a reversible capacity of 1931 mAh g −1 at 0.2 A g −1 and still remains 92% of the initial capacity after 50 cycles. [ABSTRACT FROM AUTHOR]

A key issue to design highly efficient photoelectrodes for hydrogen production is how to prohibit the rapid carrier recombination. In order to use the visible light and reduce the recombination of electrons and holes, reduced TiO 2−x /BiOCl heterojunctions are successfully synthesized and the photoelectrodes are assembled in this work. The effects of various Bi/Ti molar ratios on the structural, morphological, optical, photoelectrochemical and photocatalytic activities of the resultant samples are investigated systematically. The TiO 2−x nanoparticles contain Ti 3+ , Ti 2+ , and oxygen vacancies (Ov), while the BiOCl nanosheets exposed {001} facet. Ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) results indicate that the existence of Ti 3+ , Ti 2+ and Ov expand the light-response range. Linear scan voltammetry and electrochemical impedance spectroscopy results indicate that more efficient electron transportation is presented in the heterojunctions with the appropriate Bi/Ti molar ratio. Consequently, the reduced TiO 2−x /BiOCl heterojunction with the most appropriate Bi/Ti molar ratio exhibits a high photocurrent density of 0.755 mA cm −2 with photoconversion efficiency up to 0.634%, 10.5 and 22.6 times larger than that of pure TiO 2 and BiOCl. Furthermore, this heterojunction exhibit 48.38 and 12.54 times enhancement for the visible-light decomposition of rhodamine B compared with pure TiO 2 and BiOCl. [ABSTRACT FROM AUTHOR]

Binder-free composites of electrochemically reduced graphene oxide (ecrGO) and multiwalled carbon nanotubes (MWCNTs) were fabricated as supercapacitors electrodes operating in aqueous systems. GO was found to be electrochemically reduced according to the XRD and Raman data. Therefore, this facile and controllable method was applied to reduce GO in the GO/MWCNTs composites, generating ecrGO/MWCNTs composites. The ecrGO/MWCNTs composites exhibit higher specific capacitance (C sp ) than ecrGO because the intercalation of MWCNTs into ecrGO sheets increases the surface areas, according to the TEM, XRD and N 2 adsorption-desorption results. The composites with different mass ratios of GO to MWCNTs (10:1, 5:1, 1:1, 1:5, 1:10) were investigated. The ecrGO/MWCNTs composite (GO: MWCNTs = 5:1) showed the highest C sp from the cyclic voltammetry results at a scan rate of 10 mV s −1 , and it expressed C sp of 165 F g −1 at a current density of 1 A g −1 and 93% retention after 4000 cycles of charge/discharge. When the mass ratio of GO to MWCNTs further decreases to 1:10, the C sp of the composites declines, and the ecrGO/MWCNTs composite (GO: MWCNTs = 1:10) performs a nearly pure double-layer capacitor. However, the composites containing more MWCNTs can maintain better capacitive behavior at higher rates of charge/discharge. [ABSTRACT FROM AUTHOR]

Polyol approach is commonly used in synthesizing Pt nanoparticles in polymer electrolyte membrane fuel cells. However, the application of this process consumes a great deal of time and energy, as the reduction of precursors requires elevated temperatures and several hours. Moreover, the ethylene glycol and its oxidizing products bound to Pt are difficult to remove. In this work, we utilize the advantages of ethylene glycol and prepare Pt nanoparticles through a room-temperature hydrogen gas reduction in an ethylene glycol/water mixed solvent, which is followed by subsequent harvesting by carbon nanotubes as electrocatalysts. This method is simple, facile, and time-efficient, as the entire room-temperature reduction process is completed in a few minutes. As the solvent changes from water to an ethylene glycol/water mix, the size of Pt nanoparticles varies from 10 to 3 nm and their shape transitions from polyhedral to spherical. Pt nanoparticles prepared in a 1:1 volume ratio mixture of ethylene glycol/water are uniformly dispersed with an average size of ∼3 nm. The optimized carbon nanotube-supported Pt electrocatalyst exhibits excellent methanol oxidation and oxygen reduction activities. This work demonstrates the potential use of mixed solvents as an approach in materials synthesis. [ABSTRACT FROM AUTHOR]

It is known that the reduction process influences the initial performances and durability of nickel-yttria-stabilized zirconia composite anode of the solid oxide fuel cell. In the present study, the reduction process of nickel-yttria stabilized zirconia composite anode is simulated based on the phase field method. An three-dimensional reconstructed microstructure of nickel oxide-yttria stabilized zirconia composite obtained by focused ion beam-scanning electron microscopy is used as the initial microstructure for the simulation. Both reduction of nickel oxide and nickel sintering mechanisms are considered in the model. The reduction rates of nickel oxide at different interfaces are defined based on the literature data. Simulation results are qualitatively compared to the experimental anode microstructures with different reduction temperatures. [ABSTRACT FROM AUTHOR]

The catalytic activity of noble-metal nanoparticles (NPs) often has closely connection with their sizes and geometric shape. In the work, polyhedral NPs of palladium (Pd) with controlled sizes, shapes, and different proportions of {100} to {111} facets on the surface were prepared by a seed-mediated approach. Electrochemical experiment demonstrates that the catalytic performance of the Pd nanocubes (NCs) enclosed by {100} facets is more active than Pd octahedrons enclosed by {111} facets for the hydrogen evolution reaction (HER), which is consistent with density functional theory (DFT) calculation results. Meanwhile, with the assistance of a polyethyleneimine–reduced graphene oxide (PEI–rGO) support, the examined Pd cube/PEI–rGO 50:1 (10 wt. %) electrocatalyst presents outstanding HER activity comparable with that of commercial Pt/C catalyst. This correlation between the HER catalytic activity and surface structure will contribute to the reasonable design of Pd catalysts for HER with high efficiency and low metal loading. [ABSTRACT FROM AUTHOR]

Layered nickel sulfide (NS)-reduced graphene oxide (RGO) composites are prepared via a simple microwave-assisted method and subsequent annealing in N 2 /H 2 atmosphere. A detailed array of characterization tools are used to study their morphology, structure and electrochemical performance. It was found that these composites exhibit significantly improved sodium-ion storage ability as compared with pure NS under galvanostatic cycling at a specific current of 100 mA g −1 in a potential limitation of 0.005–3.0 V. Furthermore, the composite with the RGO content of 35 wt.% achieves a high maximum reversible specific capacity of about 391.6 mAh g −1 at a specific current of 100 mA g −1 after 50 cycles. These results prove that NS-RGO composites are highly promising when applied directly as anode materials in sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Pseudocapacitive materials are known to suffer from severe capacitance loss during charging/discharging cycling. Here we report flexible all-solid-state supercapacitors (ASSSCs) based on reduced graphene oxide (rGO)/polypyrrole nanotube (PPy NT) papers prepared by a facile vacuum filtration method. It is revealed that the incorporation of rGO nanosheets can improve the electrochemical stability of PPy NT paper electrodes for pseudocapacitors. The hybrid paper electrode shows a high areal specific capacitance of 807 mF/cm 2 at 1 mA/cm 2 and a large volumetric specific capacitance of 94.3 F/cm 3 at 0.1 A/cm 3 . The assembled ASSSC possesses a maximum areal specific capacitance of 512 mF/cm 2 at 1 mA/cm 2 and a maximum volumetric specific capacitance of 59.9 F/cm 3 at 0.1 A/cm 3 . Moreover, it also exhibits excellent rate capability (86.3% capacitance retention from 1 to 10 mA/cm 2 ) and cycling stability, little capacitance deviation under different bending states, a small leakage current and a low self-discharge characteristic. The device can provide an areal energy density of 61.4 μWh/cm 2 at 10 mW/cm 2 and a volumetric energy density of 7.18 mWh/cm 3 at 1.17 W/cm 3 , indicating this high-performance ASSSC is a promising candidate for flexible high-power supply devices. [ABSTRACT FROM AUTHOR]

The polysulfide ions formed during the first reduction wave of sulfur in Li–S battery were determined through both in-situ and ex-situ derivatization of polysulfides. By comparing the cyclic voltammetric results with and without the derivatization reagent (methyl triflate) as well as the in-situ and ex-situ derivatization results under potentiostatic condition, in-situ derivatization was found to be more appropriate than its ex-situ counterpart, since subsequent fast chemical reactions between the polysulfides and sulfur may occur during the timeframe of ex-situ procedures. It was found that the major polysulfide ions formed at the first reduction wave of elemental sulfur were the S 4 2 − and S 5 2 − species, while the widely accepted reduction products of S 8 2 − and S 6 2 − for the first reduction wave were in low abundance. [ABSTRACT FROM AUTHOR]

Carbon coated spherical Na 2 FePO 4 F particles with typical diameters from 500 nm to 1 μm have been synthesized through an economical carbothermal reduction method with a simple apparatus. Mixed carbon source consists of citric acid and phenolic resin can form highly graphitized carbon and remarkably improve the electrical conductivity. When cycled against lithium, Na 2 FePO 4 F/C cathodes deliver maximum discharge capacity of 119 mAh g −1 at a low rate of 0.05 C. Reversible capacity of 110 mAh g −1 , 74 mAh g −1 and 52 mAh g −1 can be obtained at 0.1 C, 1 C and 2 C rates, respectively. And after 30 cycles at 0.1 C, 91% of the discharge capacity can still be maintained. The electrochemical kinetic characteristic of electrode material is investigated by EIS and the apparent Li + diffusion coefficient in the Li/Na 2 FePO 4 F system is evaluated to be as high as 1.152 × 10 −11 cm 2 s −1 . This study demonstrates that the practical and economical synthesis process can be a promising way for industrial production of high performance Na 2 FePO 4 F/C electrode material for large-scale lithium ion batteries. [ABSTRACT FROM AUTHOR]

Owing to their multiple redox couples, titanium–niobium-based oxides are still considered promising candidates for use as anodes for safe, rechargeable lithium ion batteries with high energy and power densities. Titanium–niobium-based oxide electrodes have, however, exhibited relatively poor cycling performance as a result of pulverization. In this study, we report on a simple two-step solid-state reaction route for producing hybrid composites of Ti 2 Nb 10 O 29 (TNO) anchored on reduced graphene oxide (RGO), and the electrochemical performance of the resulting TNO/RGO composites. Solid-state reactions enable both the formation of TNO and the uniform distribution of RGO in the TNO/RGO composites. The TNO/RGO composites exhibited discharge and charge capacities of 261 and 256 mAh g −1 , respectively, with much better cycling performance (182 mAh g −1 after the 50th cycles) and rate capability (165 mAh g −1 at a current density of 500 mA g −1 ) compared to the pure TNO. [ABSTRACT FROM AUTHOR]

In this work, a Pd/C catalyst with high activity as well as excellent stability has been prepared by hydrogen gas reduction of Pd(II) precursor in ethylene glycol solution with the assistance of appropriate amount of sodium citrate. Pd nanoparticles with an average particle size of 3.8 nm and excellent uniformity are obtained. The Pd/C catalyst synthesized in this work shows an electrochemical surface area of 68.6 m 2 g −1 and displays activities of 819 A g −1 . Strikingly, the Pd/C catalyst also exhibits excellent stability, which has been confirmed by its slow activity decay under repeated potential cycles as well as chronoamperometric test. The activity for Pd/C at the 300 th and 500 th cycle remains at 5.5 and 2.4 mA cm −2 , respectively, which is 25% and 11% of its initial value, respectively. The oxidation currents at the Pd/C and Pd/C-Citrate (control) at 0 V decrease to 44% and 25% of their initial values. Transmission electron microscopy observations on the Pd/C catalyst after 1000 potential cycles reveal that, in addition to carbon support corrosion, Pd agglomeration together with more serious Pd dissolution occur at the same time, leading to a decrease of the electrocatalytic performance. [ABSTRACT FROM AUTHOR]

As an efficient non-precious metal catalyst for oxygen evolution reaction (OER) in electrochemical and photoelectrochemical water splitting, NiFe layered double hydroxide (LDH)/reduced graphene oxide (NiFe/RGO) composite is synthesized by a simple solvothermal method in one-pot. NiFe LDHs are uniformly deposited on RGO layers of high electrical conductivity and large surface area. In electrochemical water splitting, NiFe/RGO shows superior OER performance compared to bare NiFe and reference IrO 2 with a lower benchmark η 10 value (required overpotential to drive 10 mA cm −2 ) of 0.245 V. Furthermore, NiFe/RGO substantially increases the performance of a hematite photoanode in photoelectrochemical water oxidation, demonstrating its potential as an OER co-catalyst for photoelectrodes. [ABSTRACT FROM AUTHOR]

The process of water splitting by using efficient non-precious-metal catalyst to make the process economically viable has brought forward an extensive research. In this study, the composite of Cu and MoS 2 on the reduced graphene oxide (rGO) (Cu–MoS 2 /rGO) with high catalytic activity toward hydrogen evolution reaction (HER) was easily synthesized using hydrothermal method and chemical process. It was found that the participation of rGO improved the electrical conductivity of the catalyst, and the MoS 2 nanoflowers (NFs) with a higher number of exposed edges exhibited higher HER activity. In addition, the addition of Cu particles could not only enhance the electrical conductivity of the catalyst, but also further improved the catalytic activity by synergistic effect with MoS 2 NFs. Electrochemical experiments demonstrated that the catalyst exhibited excellent HER activity with large cathode currents and a Tafel slope as small as 90 mV decade −1 . Furthermore, it was discovered that the current density of this composite catalyst had a little decrease after the continual 700 cycling, which showed the catalyst had a high stability in the recycling process. These findings confirmed that this catalyst was a useful and earth-abundant material for water splitting. [ABSTRACT FROM AUTHOR]

Palladium–copper nanoparticles (Pd–Cu NPs) supported on reduced graphene oxide (RGO) with different Pd/Cu ratios (Pd–Cu/RGO) were prepared by a two step method. The Pd–Cu/RGO hybrids were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and thermogravimetric analyses. Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical activities and stabilities of the Pd–Cu/RGO catalysts for the electro-oxidation of methanol and ethanol in alkaline media. The Pd–Cu/RGO catalysts exhibited high catalytic activities and good stabilities. This is because the catalysts have a bimetallic structure consisting of a small Pd–Cu core surrounded by a thin Pd-rich shell which improves the catalytic activities of the Pd–Cu/RGO hybrids. Thus they should be useful in direct methanol and ethanol fuel cells. [ABSTRACT FROM AUTHOR]

Selenium nanoparticles are encapsulated uniformly with reduced graphene oxide (Se@RGO) by a simple self-assembly process. The Se@RGO composite has as high as 80 wt% of Se, which is much larger than that of other selenium-based cathode materials. The Se@RGO cathode delivers high capacity and rate capability in a Li–Se battery because of the large capacity of Se, highly dispersed Se nanoparticles in the RGO framework and high conductivity of Se and RGO nanocomposite cathode. A large initial discharge capacity of 533 mAh g −1 at 0.2C was produced based on the total mass of Se@RGO nanocomposites and the capacity could remain at 265 mAh g −1 after 200 cycles at 0.2C and additional 300 cycles at 1C. The electrode also shows an excellent capacity of 250 mAh g −1 at 5C (∼3.4 A g −1 ). The superior electrochemical performance suggests that the Se@RGO composite is a promising cathode in high-energy and high-power Li–Se battery. [ABSTRACT FROM AUTHOR]

The electrical properties of nickel-zirconia cermets as the anode material for solid oxide fuel cells (SOFCs) were studied for Sc 2 O 3 –Al 2 O 3 -stabilized ZrO 2 (SASZ), together with conventional Y 2 O 3 -stabilized ZrO 2 (YSZ). The reduction behavior of the cermets in terms of achieving better electrical conductivity was examined under constant temperature ramp rate (CTR) and constant temperature (CT) conditions. The reduction process and electrical conduction thus obtained were affected by the NiO particle size and porosity, and the zirconia composition of the starting NiO-zirconia composite material. All the NiO-zirconia anodes examined in this study exhibited high conductivity after reduction at a CT of 800 °C. The CTR condition resulted in lower electrical conductivity for the Ni-zirconia cermet. In particular, NiO-SASZ using coarse NiO powder exhibited only ionic conduction with a low electronic contribution, which was due to the absence of nickel–nickel percolation. Thermogravimetric analysis of the NiO reduction indicated that NiO-SASZ and NiO-YSZ had different reduction mechanism which might correspond to the interaction between NiO and zirconia and the long-term stability of these cermets. A kinetic analysis of the NiO reduction process revealed that fast and constant nucleation during the initial stage of reduction is important for the construction of nickel–nickel connections in the cermets. [ABSTRACT FROM AUTHOR]

In this work, a simple, rapid and facile one-pot wet-chemical co-reduction method is developed for synthesis of bimetallic Au–Pt alloyed nanochains supported on reduced graphene oxide (Au–Pt NCs/RGO), in which caffeine is acted as a capping agent and a structure-directing agent, while no any seed, template, surfactant or polymer involved. The as-prepared nanocomposites display enlarged electrochemical active surface area, significantly enhanced catalytic activity and better stability for methanol and ethylene glycol oxidation, compared with commercial Pt–C (Pt 50 wt%), PtRu–C (Pt 30 wt% and Ru 15 wt%) and Pt black. [ABSTRACT FROM AUTHOR]

Bioelectricity generated from the microbial fuel cell (MFC) is applied to the bioelectrical reactor (BER) directly to enhance microbial reduction of vanadium (V) (V(V)) in groundwater. With the maximum power density of 543.4 mW m −2 from the MFC, V(V) removal is accelerated with efficiency of 93.6% during 12 h operation. Higher applied voltage can facilitate this process. V(V) removals decrease with the increase of initial V(V) concentration, while extra addition of chemical oxygen demand (COD) has little effect on performance improvement. Microbial V(V) reduction is enhanced and then suppressed with the increase of conductivity. High-throughput 16S rRNA gene pyrosequencing analysis implies the accumulated Enterobacter and Lactococcus reduce V(V) with products from fermentative microorganisms such as Macellibacteroides . The presentation of electrochemically active bacteria as Enterobacter promotes electron transfers. This study indicates that application of bioelectricity from MFCs is a promising strategy to improve the efficiency of in-situ bioremediation of V(V) polluted groundwater. [ABSTRACT FROM AUTHOR]

Herein, we present a highly photoactive photoanode for solar water oxidation using three dimensional (3D) urchin-like hematite (α-Fe 2 O 3 ) nanostructures modified with ultra-thin reduced graphene oxide (rGO). rGO acts as both electron conducting scaffold and surface passivation layer. By virtue of these combined effects, the composite photoanode exhibits 1.47 times higher photocurrent density (1.06 mA cm −2 , at 1.23 V vs . reversible hydrogen electrode (RHE)) and two-fold enhancement in the photoconversion efficiency than that of pristine α-Fe 2 O 3 . The dual effect of rGO as both electron conducting scaffold and surface passivation layer is further evidenced from the 1.82 and 1.67 fold enhancements in charge separation and charge injection efficiencies at 1.23 and 1 V vs . RHE respectively. To get further evidence about the origin of the improved photoactivity of the rGO modified photoanode, a series of electrochemical, photoelectrochemical and impedance spectroscopy measurements were carried out. Our results demonstrate the benefits of a noble metal free highly promising photoanode for photoelectrochemical water oxidation. [ABSTRACT FROM AUTHOR]

The oxidation and reduction of water is a key challenge in the production of chemical fuels from electricity. Reported here is a soluble cobalt (II) complex, [Co(bpbH 2 )Cl 2 ] 1 (bpbH 2 : N,N′-bis(2′-pyridinecarboxamide)-1,2-benzene), a highly active homogeneous electrocatalyst for both electrolytic water oxidation and reduction in purely aqueous solution. Electrochemical studies indicate that the catalyst is a water-soluble molecular species, that is among the most rapid homogeneous catalysts for water oxidation, with a turnover frequency of ∼81.54 s −1 (at pH 8.6, the lowest pH among those of any reported electrocatalysts) at an overpotential of 560 mV. 1 also can catalyze hydrogen evolution from water with a TOF of 376 mol of hydrogen per mole of catalyst per hour at an overpotential of 687.6 mV (pH 7.0). This is attributed to the planar ligand (bpbH 2 ), that coordinates strongly through four nitrogen atoms to the cobalt center, leaving two Cl − ions in axial position and making the Cl − ion ionize in organic solvents or water, and can stabilize both the high and low oxidation states of cobalt well. [ABSTRACT FROM AUTHOR]

Ti 3+ self-doped titanium–zinc hybrid oxides with different phase compositions and morphologies were successfully synthesized using Zn powder as the reductant and Zn source by a chemical-reduction precipitation method with subsequent thermal treatment. The fabricated Ti 3+ self-doped TiO 2 (A)/TiO 2 (R), TiO 2 (A)/TiO 2 (R)/ZnTiO 3 , and TiO 2 (A)/ZnO heterojunctions were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–Vis diffuse reflectance spectroscopy. The effects of various Ti/Zn molar ratios and preparation processes on the structural, morphological, optical, photocurrent and photocatalytic properties of the resultant samples were investigated systematically. Results reveal that Ti 3+ self-doping enhances the photoabsorption capability of titanium–zinc hybrid oxides in the visible-light region. Moreover, different processes and Ti/Zn molar ratios play great influences on the structure, morphology, optical, photocurrent and photocatalytic properties of the final products. Ti 3+ self-doped titanium–zinc hybrid oxides exhibit excellent photocurrent and photocatalytic activity than pure TiO 2 and ZnTiO 3 under visible-light irradiation (λ ≥ 400 nm). The most active Ti 3+ self-doped titanium–zinc hybrid oxides photoanode presents significantly improved water splitting performance. The synergistic effect between the Ti 3+ self-doped and heterojunctions is responsible for the enhanced performance of these materials. [ABSTRACT FROM AUTHOR]

Using hierarchically mesoporous silica spheres as a hard template and methyl violet as carbon and nitrogen source, nitrogen-doped hierarchically porous carbon spheres (N-HCS) are successfully prepared via a nanocasting method. The nitrogen-doped carbon spheres obtained after carbonization at 1000 °C (N-HCS-1000) exhibit a hierarchically micro-meso-macroporous structure with a relatively high surface area (BET) of 1413 m 2 g −1 and a notably large pore volume of 2.96 cm 3 g −1 . In an oxygen reduction reaction (ORR) in alkaline media, the N-HCS-1000 material exhibits excellent activity with high current density, and its onset potential is notably close to that of the commercial Pt/C catalyst. The efficient catalytic activity of this catalyst could be attributed to the high electrical conductivity of the nitrogen-doped carbon matrix as well as the hierarchically porous framework. This catalyst also exhibits better methanol crossover resistance and higher stability than the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

This work explores low cost methods for the preparation of Si/nano-graphite sheets (NanoGs) composite materials for Li ion battery. The Si/NanoGs composites are prepared by magnesium thermal reduction of mechanical mixture of fumed SiO 2 and NanoGs under Ar atmosphere. The structure of the samples is characterized by XRD, Raman spectroscope, SEM, and HRTEM. The results show that highly crystallized Si nanoparticles with a sheet-like morphology are uniformly distributed on the surface of NanoGs (both edge and a-b plane). The average diameter of Si nanoparticles is ∼20 nm. Electrochemical characterization shows that an electrode has an initial lithium storage capacity of 1702.9 mAh g −1 at a current of 100 mA g −1 . The storage capacity decreases to 975.7 mAh g −1 after 100 cycles. Since cheap commercial fumed SiO 2 and graphite are used and the process is simple and easy to scale up, with further improvement, the method has potential for use in large scale production of high energy density Si/NanoGs anode materials at low cost. [ABSTRACT FROM AUTHOR]

Homogeneous distribution of cube-shaped Pd nanocrystals on the surface of reduced graphene oxide is obtained via a facile one-step method by employing AA and KBr as the reductant and capping agent, respectively. The experimental factors affecting the morphology and structure of Pd nanoparticles have been systematically investigated to explore the formation mechanism of Pd nanocubes (PdNCs). It is revealed that PdNCs enclosed by active {100} facets with an average side length of 15 nm were successfully synthesized on the surface of reduced graphene oxide. KBr plays the role for facet selection by surface passivation and AA controls the reduction speed of Pd precursors, both of which govern the morphology changes of palladium nanoparticles. In the further electrochemical evaluations, the Pd nanocubes/reduced graphene oxide composites show better electrocatalytic activity and stability towards the electro-oxidation of ethanol than both reduced graphene oxide supported Pd nanoparticles and free-standing PdNCs. It could be attributed to the high electrocatalytic activity of the dominated active {100} crystal facets of Pd nanocubes and the enhanced electron transfer of graphene. The developed approach provide a versatile way for shape-controlled preparation of noble metal nanoparticles, which can work as novel electrocatalysts in the application of direct alcohols fuel cells. [ABSTRACT FROM AUTHOR]

Small amount of reduce graphene oxide (rGO) nanosheets modified Li 4 Ti 5 O 12 nanoparticles composite has been synthesized by a facile and environmental in-situ hydrothermal reaction with subsequent annealing. The small amount of rGO (only 1.2 wt. %) greatly improves the whole morphology and electrochemical performance of composite. The nanoparticles uniformly grow on the rGO nanosheets effective suppressing the agglomeration and enhancing the specific surface area. Meanwhile, the special discharge capacity is 187 mAh g −1 at 1 C and the high rates discharge capacity is 128 mAh g −1 at 80 C (discharge-charge time only 33s). In particular, the cells remain in good work condition after 2000 cycles at 80 C, which credibly evidence the excellent electrochemical performance as an anode for high-power LIBs. [ABSTRACT FROM AUTHOR]

Vertically oriented graphene-based nanocatalysts represent an emerging class of electrocatalysts due to their large surface area and excellent electrical transport ability. Herein, we report a vertically oriented reduced graphene oxide supported dealloyed palladium–copper nanoparticle catalyst (PdCu/VrGO) synthesized by a facile cyclic voltammetric electrodeposition of graphene oxide in the presence of Na 2 PdCl 4 and copper ethylenediamine tetraacetate. The structure and composition are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Meanwhile, the electrochemical properties are measured by cyclic voltammetry and chronoamperometry. The PdCu/VrGO catalyst exhibits excellent electrocatalytic activity towards methanol oxidation, with the mass activity of 762.8 A g −1 , which is 7.1 times that of a commercial Pd/C catalyst. In addition, PdCu/VrGO shows good chemical stability and superior tolerance to CO poisoning. These results demonstrate that vertical reduced graphene oxide provides a promising platform for the development of electrochemical nanocatalysts. [ABSTRACT FROM AUTHOR]

Nitrogen-doped reduced graphene oxide (N-rGO) has been synthesized using a simple, efficient method combining instant thermal exfoliation and covalent bond transformation from a melamine-graphene oxide mixture. The capacitive performance of N-rGO has been tested in both aqueous (0.5 M H 2 SO 4 ) and organic (1 M tetraethyl-ammonium tetrafluoroborate (TEABF 4 ) in propylene carbonate (PC)) electrolytes, which are compared with those obtained from thermal-reduced graphene oxide (T-rGO) and chemical-reduced graphene oxide (C-rGO). The contributions of scan-rate-independent (double-layer-like) and scan-rate-dependent (pseudo-capacitance-like) capacitance of all reduced graphene oxides in both aqueous and organic electrolytes were evaluated and compared. The results show that relatively rich oxygen-containing functional groups on C-rGO form significant ion-diffusion barrier, resulting in worse electrochemical responses in organic electrolyte. By contrast, the N-doped structures, large surface area, and lower density of oxygen-containing groups make N-rGO become a promising electrode material for organic electric double-layer capacitors (EDLCs). The capacitance rate-retention of N-rGO reaches 71.1% in 1 M TEABF 4 /PC electrolyte when the scan rate is elevated to 200 mVs −1 , demonstrating that N-rGO improves the relatively low-power drawback of EDLCs in organic electrolytes. The specific energy and power of a symmetric N-rGO cell in the organic electrolyte reach 25 Wh kg −1 and 10 kW kg −1 , respectively. [ABSTRACT FROM AUTHOR]

LiNi 0.5 Mn 1.5 O 4 (LNMO) composite electrodes having the same formulation as to percentage of active material mass, binder and carbons, including reduced graphene oxide, were characterized in EC: DMC – 1M LiPF 6 by cyclic voltammetry, charge/discharge cycles and impedance spectroscopy. The results demonstrate the beneficial effect on the electrode cycling stability in increasing C-rate to 1C, in limiting the charge voltage at 4.8 V and in covering the LNMO by partially reduced graphene oxide. The paper also discusses the evaluation of lithium diffusion coefficient in LNMO from cyclic voltammetry data in regard to the discrepancies reported in literature on this matter. [ABSTRACT FROM AUTHOR]

Reduction of the precious metal catalyst loading, especially in the cathode, is critical for the development of passive direct methanol fuel cells (DMFCs). Herein, a Pt nanorod assemblies based double-layered cathode is reported with significant catalyst loading reduction up to 50%. The nanorods, consisting of linear aggregates of Pt nanoparticles, are prepared from platinum carbonyl complexes and assembled on top of a Pt/C catalyst layer for the double-layered cathode fabrication. The maximum power density of a passive DMFC with the double-layered cathode, using 2.0 M methanol and at a temperature of 25 °C, is ca. 39.4 mW cm −2 at a Pt loading of 2.0 mg cm −2 ; and it is ca. 29.1 mW cm −2 at a Pt loading of 1.0 mg cm −2 comparable to that with only a conventional Pt/C layer at a Pt loading of 2.0 mg cm −2 . The improved cell performance is ascribed to increased catalyst utilization and decreased charge-transfer resistance in the double-layered cathode as confirmed by electrochemical characterization and equivalent circuit analysis. The Pt nanorod assemblies based systems hold great potential for the cost reduction of DMFCs. [ABSTRACT FROM AUTHOR]

A small sized TiO 2 nanocrystal (∼10 nm)/reduced graphene oxide (TiO 2 /rGO) hybrid is synthesized through a sol–gel process for hybrid TiO 2 /GO followed by solvothermal reduction of GO to rGO and is further used as a microbial fuel cell (MFC) anode. The strong synergistic effect from a large surface area produced by uniformly deposited TiO 2 nanocrystals, good hydrophilicity of TiO 2 nanocrystals and superior conductivity of rGO leads to significantly improved electrocatalysis. In particular, a direct electrochemistry is realized by generating endogenous flavins from a large amount of microbes grown on the highly biocompatible TiO 2 nanocrystals to mediate fast electron transfer between microbes and conductive rGO for a high performance anode. The TiO 2 /rGO hybrid anode delivers a maximum power density of 3169 mW m −2 in Shewanella putrefaciens CN32 MFC, which is much large than that of the conventional carbon cloth anode and reported TiO 2 /carbon hybrid anode, thus offering great potential for practical applications of MFC. This work is for the first time to report that the synergistic effect from tailoring the physical structure to achieve small sized TiO 2 nanocrystals while rationally designing chemistry to introduce highly conductive rGO and superior biocompatible TiO 2 is able to significantly boost the MFC performance. [ABSTRACT FROM AUTHOR]

Submicron-structured Li 3 V 2 (PO 4 ) 3 /C has been synthesized by carbon-thermal reduction method with poly(acrylic acid) and d -(+)-glucose as carbon sources. The pure monoclinic structure of Li 3 V 2 (PO 4 ) 3 /C has been confirmed by XRPD and Rietveld refinement, scanning electron microscopy, and transmission electron microscopy. The specific capacity of Li 3 V 2 (PO 4 ) 3 /C as cathode has been evaluated, between 3.0 and 4.3 V vs Li + /Li, in the two different electrolytes: 1 M solution of LiPF 6 in EC:DMC (1:1) at room temperature and in EC:DMC:DEC (1:1:1) at low temperature (0 and −20 °C). Because of the submicron-size dimensions of Li 3 V 2 (PO 4 ) 3 and of the good carbon coating, the material discharge capacities as high as 103, 98 and 81 mAh g −1 at 40, 60 and 100C rates, retains 93% of the initial discharge capacity after 1000 cycles at 100C. The performances even at low temperature are also good with values of the order of 84, 40, 23, 19 mAh g −1 at 0 °C and 69, 24, 19, 15 mAh g −1 at −20 °C at 3, 7.5, 15, 30 C-rates, respectively. [ABSTRACT FROM AUTHOR]

A detailed processing cost breakdown is given for lithium-ion battery (LIB) electrodes, which focuses on: 1) elimination of toxic, costly N -methylpyrrolidone (NMP) dispersion chemistry; 2) doubling the thicknesses of the anode and cathode to raise energy density; and 3) reduction of the anode electrolyte wetting and SEI-layer formation time. These processing cost reduction technologies generically adaptable to any anode or cathode cell chemistry and are being implemented at ORNL. This paper shows step by step how these cost savings can be realized in existing or new LIB manufacturing plants using a baseline case of thin (power) electrodes produced with NMP processing and a standard 10–14-day wetting and formation process. In particular, it is shown that aqueous electrode processing can cut the electrode processing cost and energy consumption by an order of magnitude. Doubling the thickness of the electrodes allows for using half of the inactive current collectors and separators, contributing even further to the processing cost savings. Finally wetting and SEI-layer formation cost savings are discussed in the context of a protocol with significantly reduced time. These three benefits collectively offer the possibility of reducing LIB pack cost from $502.8 kW h −1 -usable to $370.3 kW h −1 -usable, a savings of $132.5/kWh (or 26.4%). [ABSTRACT FROM AUTHOR]

Herein, we present a new strategy for the mass production of high-quality reduced graphene oxide (RGO) with a surface area of 354 m 2 g −1 using high pressure hydrogen as a reducing agent under hydrothermal conditions. The high pressure used is solely generated from the packing of the gas cylinder itself and a pressure meter could simply fulfil the role of monitoring pressure. The reduction process is green without chemical wastes produced. Comparing to other reported methods, the significant advancements of our strategy lie not only in the high-quality RGO with high C/O ratio, conductivity and surface area, but also in the most environment-friendliness and cost-effectiveness, which make the large scale fabrication feasible. Moreover, clean noble metal nanocrystals such as Pt could be easily in situ deposited onto the surface of RGO nanosheets when noble metal salts are introduced into the system. In particular, the prepared RGO and Pt/RGO show exceptional electrochemical performances in supercapacitors and lithium oxygen batteries because of their clean electrochemical surface, good conductivity and large surface area. Our results reveal that the obtained RGO have a specific capacitance of 884.4 F g −1 at a current density of 0.5 A g −1 , and the Pt/RGO electrode can deliver discharge–charge capacities of 1000 mAh g −1 for 40 cycles with a high round-trip efficiencies of 74.9% at 50 mA g −1 when used as Li–O 2 battery electrodes. [ABSTRACT FROM AUTHOR]

The restacking-inhibited N-doped graphene (GN) is prepared for supercapacitor material based on the sol–gel method. Meanwhile, the graphene oxide (GO) is reduced and modified by melamine-resorcinol-formaldehyde (MRF). The reduced graphene oxide (RG) is characterized with the ultraviolet visible absorption spectrum, Raman spectra and X-ray diffraction. Moreover, the morphology of GN is measured by scanning electron microscopy, transmission electron microscopy and nitrogen adsorption. The doped N content is confirmed by elemental analysis and X-ray photoelectron spectroscopy. The result shows that GO is reduced by resorcinol derivatives. With the specific surface of 518 m 2 g − 1 and N content of 9.77 wt%, laminated GN with 2.5 wt% GO exhibits the outstanding specific capacitance (245 F g −1 ), low charge-transfer resistance and superior cycle stability (94.8% retention after 2000 cycles). [ABSTRACT FROM AUTHOR]

In this work, copper and nickel oxides (CuO–NiO) powders with various mole ratios were synthesized by the glycine nitrate process (GNP) and the Cu–Ni alloy was obtained by reducing the CuO–NiO powders at 600 °C for 0.75 h. Furthermore, Cu 1−x Ni x (alloy) -CeO 2 impregnated YSZ anodes were fabricated by the impregnation method and the optimized anode composition was evaluated. It was found that the optimized mole ratio of Cu:Ni was 5:5, while the weight ratio of Cu–Ni alloy to CeO 2 was 3:1. Additionally, impregnated anode with 40 wt % loading of Cu 0.5 Ni 0.5 (alloy)-CeO 2 exhibited the best performance and the polarization resistance of such anode was only 0.097, 0.115, 0.145 and 0.212 Ω cm 2 at 750, 700, 650 and 600 °C, respectively. Finally, the performance of the optimized anode in methane (CH 4 ) was investigated and the carbon deposition is greatly suppressed compared to the Ni-based anode. [ABSTRACT FROM AUTHOR]

A novel bimetallic Pt–Fe electrode supported on carbon fibers (CFs) was prepared by chemical impregnation/reduction and evaluated for the electrolysis of coal to produce hydrogen. Characterization of the electrocatalyst was performed using X-ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive Spectroscopy. The synthesized Pt–Fe particles were well dispersed on the surface of the CFs. The addition of Fe to the catalyst enhanced the electrooxidation of coal when compared to Pt alone. PtFe (1:1) supported on carbon fibers exhibited superior catalytic activity towards the conversion of coal than PtFe (7:3) and PtFe (3:7). [ABSTRACT FROM AUTHOR]

Carbon counter electrodes for dye-sensitized solar cells (DSSCs) have attracted strong attention due to their low material cost and practically high power conversion efficiency (PCE). However, there were issues in PCE stability observed during durability tests. In this study, H 2 -reduced carbon counter electrode for low cost DSSCs is introduced and demonstrated improved durability over the conventional carbon electrodes, with the absolute PCE value of 7.7%. It was found that carbon resistance decay ratio improved compared to those without H 2 -reduction process. These cells after the durability test were disassembled, and surface adsorptions on the carbon counter electrodes were analyzed. The adsorption of compounds originated from the dye and co-adsorbents on the H 2 -reduced carbon electrode was largely reduced, due to the cleaning of surface functional groups that can adsorb large molecules. These results suggest that H 2 -reduction process proposed in this work effectively reduces surface adsorptions on carbon electrode, and as a result improves the durability of DSSCs. [ABSTRACT FROM AUTHOR]

This work is to study the reasons for the relatively low efficiency of sulphur reduction (about 75%) in lithium–sulphur batteries. The two main reasons for that are suggested to be: the relatively low electrochemical activity of low order lithium polysulphides and blocking of the carbon framework of the sulphur electrode by insoluble products of electrochemical reactions – sulphur and lithium sulphide. The electrochemical activity of lithium polysulphides with different composition (Li 2 S n , n = 2–6) has been studied in 1 M solutions of CF 3 SO 3 Li in sulfolane. It is shown that lithium polysulphides including lithium disulphide are able to electrochemically reduce with efficiency close to 100%. The electrochemical activity of lithium polysulphides decreases with the order. The order of lithium polysulphides affects the value of voltage of discharge plateaus but not the efficiency of sulphur reducing in the lithium polysulphides species. The relatively low efficiency of sulphur reduction in the lithium–sulphur batteries is more likely caused by blocking of carbon particles in the sulphur electrode by insoluble products of electrochemical reactions (sulphur and lithium sulphide). This prevents the electrochemical reduction of low order lithium polysulphides and especially lithium disulphide. [ABSTRACT FROM AUTHOR]

Enhancement in power conversion efficiency is a persistent pursuit for solid-state dye-sensitized solar cells (DSSCs). We report an experimental strategy of synthesizing I − /I 3 − doped 3-hydroxypropionitrile/polyaniline (HPN/PANi) solid electrolytes, aiming at expanding I 3 − reduction reaction from electrolyte/counter electrode interface to solid electrolyte system and shortening the charge diffusion path length. The DSSC with HPN/1.0 wt% PANi shows an efficiency of 3.70% in comparison to 1.49% from the cell with pristine HPN. [ABSTRACT FROM AUTHOR]

Splitting water is a key challenge in the production of chemical fuels from electricity. Although several catalysts have been developed for these reactions, substantial challenges remain towards the ultimate goal of an efficient, inexpensive and robust electrocatalyst. Until now, there is as yet no report on both water oxidation and reduction by identical catalyst. Reported here is the first soluble copper-based catalyst, Cu(Me 2 oxpn)Cu(OH) 2 ] 1 (Me 2 oxpn: N,N′-bis(2,2′-dimethyl-3-aminopropyl)oxamido) for both electrolytic water oxidation and reduction. Water oxidation occurs at an overpotential of 636 mV vs SHE to give O 2 with a turnover frequency (TOF) of ∼2.14 s −1 . Electrochemical studies also indicate that 1 is a soluble molecular species, that is among the most rapid homogeneous water reduction catalysts, with a TOF of 654 mol of hydrogen per mole of catalyst per hour at an overpotential of 789 mV vs SHE (pH 7.0). Sustained water reduction catalysis occurs at glassy carbon (GC) to give H 2 over a 32 h electrolysis period with 95% Faradaic yield and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

High-performance supercapacitor electrodes with a novel hierarchical structure of MnO 2 /ZnO/carbon-fabric were rationally designed, and prepared by a simple three-step-solution method. The design comprises ZnO nanowires radially grown on each micron-size fiber of a carbon-fabric electrode, with a thin MnO 2 shell on each ZnO nano-core. This multi-scale hierarchical structure yields: (a) high specific area of pseudo-capacitive MnO 2 to maximize specific capacitance; (b) effective MnO 2 -electrolyte interface to facilitate fast charging/discharging; and (c) conductive MnO 2 –ZnO-electrode path to reduce energy loss. In addition, the overall capacitor performance is optimized by choosing proper thickness of MnO 2 shell and aspect ratio of ZnO nano-core. The design was realized and validated with the development of a simple three-step-solution method: (a) radial deposition of nano-ZnO on carbon fabric; (b) coating ZnO by a thin layer of carbon; and (c) reduction of MnO 4 − and replacement of this carbon overlayer by MnO 2. With this design and method, high specific capacitance of 886 F g −1 was found from electrodes with 5 nm MnO 2 on ZnO having an average diameter of 50 nm and aspect ratio of 30. These samples showed specific energy of 16 Wh kg −1 and specific power of 27 kW kg −1 at current density of 20 mA cm −2 , and good long-term cycling stability. [ABSTRACT FROM AUTHOR]

An innovative design, alternative to the conventional metal supported fuel cells (MSC) is proposed. This new design of Solid Oxide Fuel Cell (SOFC), comprises a 200 μm layer of a honeycomb-metallic framework with hexagonal cells which supports a 250 μm layer of electrolyte. Each hexagonal cell is further functionalized with a thin 5–10 μm of Ni–YSZ anode. This new design allows a reduction of ∼65% of the metallic supporting material, rendering performances over 300 mW cm −2 under pure hydrogen at 850 °C, with an OCV of ∼1.1 V. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy) has been polymerized onto reduced graphene oxide/carbon nanotube (rGO/CNT) to form an rGO/CNT/PPy composite using the chemical oxidation method. The electrochemical characteristics of the above composite in various aqueous electrolytes are systematically compared for the asymmetric supercapacitor application. The electrochemical characteristics of rGO/CNT/PPy in the electrolytes containing K + show improved reversibility and higher stability. Introducing XC-72 in preparing the electrode has been found to enhance the specific capacitance and the cycle stability of rGO/CNT/PPy. The charge storage stability of rGO/CNT/PPy + XC-72 in various potential windows has been evaluated through the potential bias stress test. An asymmetric supercapacitor (ASC) with a positive electrode of Mn 3 O 4 and a negative electrode of rGO/CNT/PPy + XC-72 is successfully demonstrated, which shows specific energy and power of 14. Wh kg −1 and 6.62 kW kg −1 with a cell voltage of 1.6 V. This ASC with a cell voltage of 1.6 V shows excellent charge–discharge cycle stability and ideal capacitive behavior in NaNO 3 even after the application of 3250 charge–discharge cycles. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbons (HPCs) are prepared by a one-step hydrothermal route using soluble resols as a carbon source, polystyrene spheres and Pluronic F127 as macroporous and mesoporous templates, respectively. The resulting HPCs comprise continuous macro–meso–micropore networks on the carbon blocks, simultaneously exhibiting large surface areas (501–709 m 2 g −1 ), which are particularly evaluated as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). Electrochemical impedance spectra (EIS), Tafel polarization curves, and cyclic voltammograms (CVs) demonstrate that the hierarchical pore system plays a crucial role in promoting the catalytic activities of the HPC CEs. In comparison with other porous carbon CEs, the HPC CEs with various macropores and appropriate micro/mesopores present better catalytic behaviors due to the easier accessibility for electrolyte ions and better utilization of the catalytically active sites, resulting in the higher photovoltaic conversion efficiencies of DSSCs. The optimum photovoltaic conversion efficiency of DSSCs based on HPC CEs is 7.22%, which can even match up to that of the cell with Pt CE (7.25%). [ABSTRACT FROM AUTHOR]

A potential negative electrode material Co 3 O 4 @rGO is synthesized via a facile reflux condensation route. The electrochemical performances of Co 3 O 4 @rGO composite for alkaline rechargeable Ni/Co batteries have been systemically investigated for the first time. The reduced-graphene can remarkably enhance the electrochemical activity of Co 3 O 4 materials, leading to a notable improvement of discharge capacity, cycle stability and rate capability. Interestingly, the maximum discharge capacity of Co 3 O 4 @rGO-20 (additive amount of GO is 20 mg) electrode can reach 511.4 mAh g −1 with the capacity retention of 89.1% after 100 cycles at a discharge current of 100 mA g −1 . A properly electrochemical reaction mechanism of Co 3 O 4 @rGO electrode is also constructed in detail. [ABSTRACT FROM AUTHOR]

In using a LiPF 6 /ethylene carbonate–dimethyl carbonate electrolyte for lithium ion batteries (LIBs), a certain reductive reaction is known to occur at a relatively high potential (ca. 2.6 V vs. Li + /Li) on Sn electrode, but its details are still unknown. By means of in-situ X-ray reflectometry, X-ray photoelectron spectroscopy, scanning electron microscopy observations and electrochemical measurements (by using mainly Sn electrode, and additionally Pt, graphite electrodes), we have found out that this reduction eventually forms an inactive passivation-layer consisting mainly of insulative LiF ascribed to the reductive decomposition of LiPF 6 , which significantly affects the battery cyclability. In contrast, a solid-electrolyte interphase (SEI) is formed by the reductive reaction of the solvent at ca. 1.5 V vs. Li + /Li, which is lower than the reduction potential of LiPF 6 . However, we have found that the formation of SEI preempts that of the passivation layer when holding the electrode at a potential lower than 1.5 V vs. Li + /Li. Consequently, the cyclability is improved by suppressing the formation of the inactive passivation layer. Such a pretreatment would be quite effective on improvement of the battery cyclability, especially for a relatively noble electrode whose oxidation potential is between 1.5 V and 2.6 V vs. Li + /Li. [ABSTRACT FROM AUTHOR]

Pure titanium foil cannot be directly as the substrate for the bipolar lead-acid battery due to its surface oxidized into titanium dioxide in the cell cycle. The poor electronic conductivity of titanium dioxide will increase substrate's ohmic resistance and can affect the cell's electrochemical performances. In this paper, titanium foil's surface is coated with a lay of partial reduction titanium dioxide (TiO 2− x ) which has excellent chemical stability and high electronic conductivity by means of sol–gel method. Through XRD, SEM and four-probe test, it shows that the modified titanium's surface has the most superior crystal structure and morphology and the highest electronic conductivity in the sintering temperature of 800 °C. We subsequently assemble bipolar lead-acid batteries with Ti coated by TiO 2− x as the substrate material. The batteries are discovered that when charged and discharged in 3.5 V–4.84 V at 0.5C the voltage between the charge and discharge voltage platform is 0.3 V, and the initial discharge specific capacity can reach 80 mAh g −1 . When the current rate is up to 1C and 2C, the initial discharge specific capacity is 70 mAh g −1 and 60 mAh g −1 . After 100 cycles, the initial specific capacity only decreases 12.5%. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) multilayer porous MnO 2 /reduced graphene oxide composites are coated on a nickel foam substrate (denoted as MnO 2 /R-GO@Ni-foam) by a facile and scalable spray method following by low temperature annealing. The composite electrodes are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The content of MnO 2 in the MnO 2 /R-GO@Ni-foam composites is determined by thermal gravimetric analysis. The supercapacitive performance of the composite electroides is investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The results show that the MnO 2 /R-GO@Ni-foam composite displays a high specific capacitance of 267 F g −1 at 0.25 A g −1 and excellent capacitance retention of 89.5% after 1000 cycles. This study provides a facile way for the preparation of composite electrodes for high-performance supercapacitor. [ABSTRACT FROM AUTHOR]