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Abstract: Combining experimental and computational techniques can provide a better understanding of surface film formation processes that occur in the lithium-ion battery. In this paper, we show that this joint approach can provide a mechanistic understanding of the effect of oxygen in the reduction of propylene carbonate (PC). We perform FTIR analysis, inside a glove box, after conducting linear sweep voltammetry (LSV) from an open-circuit voltage (OCV) to selected potential regions; subtraction between two successive IR spectra has been made to identify the reduction products formed within each potential range. FTIR analysis in the potential range from OCV to −0.1 V, in conjunction with density functional theory (DFT) calculations, confirm the formation of solvated Li2CO3 and (PC)2LiOC(O)OCH(CH3)CH2OLi(PC) due to PC reduction. Our experimental results and DFT calculations suggest that in the potential range from OCV to 1.6 V, PC, in the presence of O2, can easily decompose by the superoxide ion through a nucleophilic attack at the ethereal carbon atom. [Copyright &y& Elsevier]

Abstract: The lithium/sulfur battery is a promising electrochemical system with high capacity, which is well-known to undergo a complex multistep reaction during the discharge process. Two types of electrolytes including poly(ethylene glycol) dimethyl ether (PEGDME)-based and 1,3-dioxolane (DOL)/dimethoxyethane (DME)-based electrolytes were investigated here. Furthermore, LiNO3 additive was introduced into the electrolyte in order to effectively eliminate the overcharge effect. The lithium sulfur battery with 1.0 M LiN(CF3SO2)2 in PEGDME with 0.1 M LiNO3 shows highly stable reversible capacity of 624.8 mAh g−1 after 200 cycles and improved average coulombic efficiency of 98%. [Copyright &y& Elsevier]

Abstract: Li[Ni0.2Li0.2Mn0.6]O2 nanoparticles are fabricated using a combustion method in which three different dispersing agents, gelatin, urea and Pluronic® P-123 (P123), are introduced as dispersing agents. The dispersing agents are used in order to disperse the primary particles during the sol–gel thermolysis process and reduce the sizes of the powder particles. Reducing the size of the particles is effective in improving the rate capability of the Li[Ni0.2Li0.2Mn0.6]O2 electrode. However, the cyclic performance deteriorates due to vigorous side reactions with the electrolyte. In order to avoid this, the surfaces of the Li[Ni0.2Li0.2Mn0.6]O2 nanoparticles, prepared using dispersing agents, are modified by a ZrO2 surface coating. A novel precoating of polydopamine is used to aid the ZrO2 coating of the nanosized particles. The surfaces of the coated Li[Ni0.2Li0.2Mn0.6]O2 particles are homogeneously covered with the ZrO2, demonstrating the effectiveness of the polydopamine precoating as a binding agent between the nanosized cathodic particles and the coating material. The cyclic performance and thermal stability of the coated Li[Ni0.2Li0.2Mn0.6]O2 nanoparticles are significantly enhanced, showing that the ZrO2 coating layer successfully protected the nanoparticles from the reactive electrolyte. [Copyright &y& Elsevier]

Abstract: We present a model of the lithium–sulfur (Li/S) battery based on a multi-step, elementary sulfur reduction mechanism including dissolved polysulfide anions. The model includes a description of the evolution of solid phases in the carbon/sulfur composite cathode as well as multi-component (Li+, , S8, , , , , S2–) mass and charge transport in the liquid electrolyte. The chemical reaction mechanism consists of a Li/Li+ oxidation reaction at the anode and a six-step polysulfide reduction mechanism at the cathode. The modeling framework allows for the simulation of charge and discharge profiles as well as electrochemical impedance spectra. The latter are obtained via a voltage step/current relaxation technique based on the physicochemical model without the need for applying equivalent circuit models. The results indicate that the discharge behavior of this Li/S cell is governed by the presence of solid reactant and product phases in exchange with the dissolved polysulfide anions. The first and last stages of the discharge are characterized by the presence of solid S8 and Li2S, respectively, while the intermediate stage corresponds to a situation where all chemical compounds are dissolved in the electrolyte. [Copyright &y& Elsevier]

Abstract: Phosphate-based compounds with the high working voltage, such as Li3V2(PO4)3, LiVPO4F and LiMnPO4, have been proposed as a new class of cathode materials for lithium-ion batteries. To improve the operating voltage of LiFePO4, we introduce LiVPO4F to prepare xLiFePO4·(1 − x)LiVPO4F (LFP–LVPF) composites through an aqueous precipitation and carbothermal reduction method. A series of LFP-LVPF composites have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and total organic carbon (TOC) analysis. The discharge capacity of LFP–LVPF composites for x:(1 − x) = 1:0, 0.99:0.01, 0.75:0.25, 0.5:0.5, 0.25:0.75 and 0:1 at a 0.2 C-rate is 153, 160, 132, 106, 92 and 78 mAh g−1, respectively. The discharge capacity decreases with increasing mole fraction of LVPF. Moreover, the operating voltage of LFP-LVPF composites for x:(1 − x) = 0.75:0.25, 0.5:0.5 or 0.25:0.75 is higher than that of LFP, and the charge/discharge plateaus around 4.35/4.15 V for LFP-LVPF composites become longer as the value of x decreases. [Copyright &y& Elsevier]

Pt colloidal nanoparticles were synthesized by simultaneous chemical reduction of metallic salts in presence of poly (N-vinyl-2-pyrrolidone) as protecting agent. The uniform and highly ordered Pt colloidal nanoparticles were associated to well dispersed particles ranging in particle size distribution around 4.5 ± 1.9 nm. The nanoparticles were deposited onto multiwalled carbon nanotubes (MWCNT). MWCNT were synthesized by chemical vapor deposition (CVD) method. Before the metal impregnation, the MWCNT were treated with HNO3 in reflux. Prepared Pt catalyst were characterized by various physical and electrochemical techniques, that is, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy and cyclic voltammetry (CV). Raman spectroscopy reveals changes intensity ratio IG′/IG in the samples, after the cleaning process and Pt loading, indicating changes in the crystallinity of the materials. HRTEM showed Pt particles between 6.1 ± 0.9 nm and 6.5 ± 1.5 nm are well dispersed along the carbon nanotubes. XRD patterns show characteristics peaks corresponding to graphite and metallic Pt. The electrochemical properties of the MWCNT supported Pt nanoparticles were investigated by analyzing the response of the nanostructured catalyst for cyclic voltammetry and compared with a commercial material. [ABSTRACT FROM AUTHOR]

Single chamber anode-supported fuel cells are investigated under several methane–oxygen–nitrogen atmospheres at intermediate temperatures (500 °C–700 °C). Ce0.9Gd0.1O1.95 (CGO) is chosen as electrolyte and deposited by screen-printing onto NiO–CGO anode pellets. A cathode composed of 70 wt% La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and 30 wt% of CGO is screen-printed onto the electrolyte. Thermogravimetric analyses of anode reduction are performed at 700 °C. Carbon deposition is observed under diluted methane but a successful reduction is obtained after an initialization under diluted methane followed by a final treatment under methane-to-oxygen ratio (R mix) of 2. Anode-supported fuel cells are investigated regarding the working temperature and R mix. Two types of cells are prepared with modifications of the electrolyte microstructure. For both cells tested, the Open Circuit Voltage (OCV), the power density and the fuel utilization increase when R mix and temperature decrease. The electrolytes of both cells have a porous microstructure and the electrolyte of the second cell, with the highest thickness, brings better performances. At 600 °C for R mix = 0.6, the maximum power density is improved from 60 for the first cell to 160 mW cm−2 for the second cell. Comparing the fuel utilization, it increases from 3% for the first cell to 6% for the second one for the same testing conditions. [ABSTRACT FROM AUTHOR]

Abstract: Supercapacitors are electrochemical energy storage devices with high power density. However, application of supercapacitors is limited mainly due to their high leakage current. In this work, application of an ultra-thin layer of electrodeposited poly (p-phenylene oxide) (PPO) has been investigated as a blocking layer to reduce the leakage current. The polymer was first deposited on a glassy carbon electrode. The morphology of the film was studied by atomic force microscopy (AFM), and the film thickness was estimated to be ∼1.5 nm by using the electrochemical impedance spectroscopy (EIS) technique. The same deposition method was applied to coat the surface of the activated carbon electrodes of a supercapacitor with PPO. The specific capacitance, the leakage current, and the series resistance were measured in two devices with and without the blocking layer. The results demonstrate that the application of the PPO layer reduced the leakage current by ∼78%. However, the specific capacitance was decreased by ∼56%, when the blocking layer was applied. Due to the lower rate of self-discharge, the suggested approach can be applied to fabricate devices with longer charge storage time. [Copyright &y& Elsevier]

Abstract: Magnetite (Fe3O4)/carbon core–shell nanotubes have been successfully synthesized by partial reduction of monodispersed hematite (Fe2O3) nanotubes with carbon coating. Fe2O3 is completely converted to Fe3O4 during the reduction process and a thin carbon layer is continuously coated on the surface of Fe3O4 with the nanotube morphology reserved. The Fe3O4/carbon core–shell nanotubes exhibit superior electrochemical properties as anode material for lithium-ion batteries compared with the Fe2O3 and Fe3O4 nanotubes. The Fe3O4/carbon core–shell nanotubes electrode shows a large reversible capacity up to 938 mAh g−1 as well as improved cycling stability and excellent rate capability. The promising anode performance of the Fe3O4/carbon core–shell nanotubes can be attributed to their tubular morphology and continuous carbon coating, which provide improved structural stability and fast charge transport. [Copyright &y& Elsevier]

Abstract: Hydrated vanadium pentoxide (V2O5·0.86H2O) nanoribbons modified with reduced graphene oxide (RGO) are synthesized by a hydrothermal process. These ribbons are 30 nm thick, 200 nm to 1 μm wide and above 50 μm long. Binder-free films are prepared by using these ribbons and annealed at 300 °C in nitrogen as the cathode for rechargeable lithium cells. The intertwining network of this free-standing VO x /RGO film provides efficient conduction pathways for electrons and short diffusion distances for Li ions. The electrochemical tests exhibit that this cathode film delivers a high reversible specific capacity (160 mAh g−1) and good cycling stability (133 mAh g−1 after 200 cycles) in the voltage range between 2.0 and 3.5 V. [Copyright &y& Elsevier]

Abstract: Tin oxide (SnO2)/graphene composite is synthesized via a simple wet chemical method using graphene oxide and SnCl2·2H2O as raw materials. Graphene of high reduction degree in the composite can provide high conductivity and large-current discharge capacity. SnO2 nanoparticles with dimension around 5 nm are uniformly distributed on the graphene matrix. The SnO2/graphene composite exhibits outstanding electrochemical performance such as high reversible capacities, good cycling stability and excellent high-rate discharge performance. The initial discharge and charge capacities are 1995.8 mAh g−1 and 1923.5 mAh g−1, respectively. After 40 cycles, the reversible discharge capacity is still maintained at 1545.7 mAh g−1 at the current density of 1 A g−1, indicating that the composite is a promising alternative anode material used for high-storage lithium ion batteries. [Copyright &y& Elsevier]

Abstract: Platinum nanoclusters were synthesized using two methods: (a) ascorbic acid reduction of K2PtCl4, (b) an H2PtCl6 polyol process. Both processes yield clusters of platinum consisting of nanoparticles with a narrow size distribution. Experiments were conducted using platinum nanoclusters as the working electrode and bulk platinum wire as the counter electrode, both supported on inert, electronically conducting substrates. The electrodes were immersed in a PtCl4 + dimethyl sulfoxide electrolyte solution. The spacing between the electrodes was maintained at 1 mm or 6 mm. Electrical potential was measured across the two electrodes as a function of time. The samples (scraped off the nano-electrode) were examined using transmission electron microscopy (TEM). Experimental data show significantly lower kinetics of particle growth for the nanoclustered, uniformly sized particles as compared to commercially available carbon-supported platinum catalysts. [Copyright &y& Elsevier]

Abstract: We have investigated the CO2 electroreduction at a Pt–Ru/C-based catalyst using a membrane electrode assembly (MEA) in a single cell to realize a methanol-based reversible fuel cell. Cyclic voltammograms were measured under N2 and CO2 atmospheres using the Pt–Ru/C-based MEA. For comparison, the Pt/C-based MEA was used. A typical voltammogram attributed to the Pt electrode has been obtained using Pt/C under an N2 atmosphere, and an extra oxidation peak appeared at 0.60 V vs. DHE under a CO2 atmosphere. This peak has been considered to be caused by the re-oxidation of the CO2 reductant. For the Pt–Ru/C, the re-oxidation peak has been observed at 0.50 V vs. DHE which is more negative than Pt/C. The limiting cathode potential of the cyclic voltammogram was changed from 0.06 to 0.35 V vs. DHE under a CO2 atmosphere, and the magnitude of the re-oxidation peak decreased. To quantitatively analyze the product of the CO2 reduction, a gas chromatograph and methanol- and CO-stripping voltammograms were measured. Based on these results, methanol has been found to be the main product of the CO2 reduction at the Pt–Ru/C. Finally, the methanol yield and coulombic efficiency were calculated resulting in 7.5% and 75% at the Pt–Ru/C, respectively. [Copyright &y& Elsevier]

Abstract: Graphene/MnO2 composites are synthesized by the chemical reduction of GO/MnO2 using both hydrazine hydrate (H-RGO/MnO2) and sodium borohydride (S-RGO/MnO2) as reducing agents. The morphology and microstructure of the as-prepared composites are characterized by X-ray diffractometry, field-emission scanning electron microscopy, Raman microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy. Characterizations indicate that MnO2 is successfully formed on the GO surface and GO is reduced successfully by using both hydrazine hydrate and sodium borohydride as reducing agents. H-RGO/MnO2 shows higher electrical conductivity than that of S-RGO/MnO2 since it has a lower concentration of oxygen-containing functional groups. The capacitive properties of the H-RGO/MnO2 and S-RGO/MnO2 electrodes are measured using cyclic voltammetry and galvanostatic charge/discharge tests and electrochemical impedance spectroscopy in a three-electrode experimental setup using a 1 M Na2SO4 aqueous solution as the electrolyte. The H-RGO/MnO2 electrode displays a specific capacitance as high as 327.5 F g−1 at 10 mV s−1, which is higher than that of the S-RGO/MnO2 electrode (278.6 F g−1). It is anticipate that the formation of nanoneedle structures of MnO2 on graphene oxide surfaces after the hydrazine reduction procedure is a promising fabrication method for supercapacitor electrodes. [Copyright &y& Elsevier]

Abstract: TiO2 nanotube arrays are modified by a facile cathodic reduction process treatment and the results are discussed in terms of their electrochemical activity and conductivity. The instrumental characterizations such as X-ray photoelectron spectroscopy and Raman spectroscopy indicate that the formation of oxygen vacancies in the lattice and introduction of hydroxyl groups on the surface of TiO2 take place. The capacitance of the modified sample is found to be 13 times larger than the pristine TiO2 nanotube arrays. This work reveals a feasible and simple method to improve electrochemical activity and conductivity of TiO2 for supercapacitors application. [Copyright &y& Elsevier]

Abstract: Reduction of the charging time for batteries is a crucial factor in the promotion of consumer interest in the commercialization of electric vehicles (EVs). Fast charging methods for EVs are therefore important to create and understand; however, fast charging is not tolerated by all lithium-ion chemistries because it typically affects the battery functionality and accelerates its aging mechanisms. A fast charging technique is proposed in this paper, and the results of extensive testing on a high power lithium iron phosphate cell subjected to the method are reported. The evaluation characterized the cell's capacity fade, cycle life, and energy efficiency with respect to the U.S. Advanced Battery Consortium (USABC) goals. The proposed charging algorithm permits a full recharging of the cell (0–100% SOC) in approximately 20 min, even after 4500 cycles are reached. The cycling scheme is characterized by high current discharges that reach specific powers of 400 W kg−1. The results show that the proposed fast charging technique does not introduce any significant degradation effects on the cell and is energy efficient; they also show that performance is lost due to capacity fade rather than an increase in internal resistance. [Copyright &y& Elsevier]

Abstract: Li3V2(PO4)3/reduced graphene oxide (designated as Li3V2(PO4)3/rGO) and Li3V2(PO4)3/reduced modified graphene oxide (designated as Li3V2(PO4)3/rmGO) nanocomposites have been synthesized by a solvothermal method, followed by post-heat treatment at 800 °C, and explored as cathodes in lithium-ion cells. Lamellar GO sheets were modified with cetyltrimethylammonium bromide (CTAB) to form mGO with good dispersibility. The Li3V2(PO4)3/rGO (∼350 nm particles) and Li3V2(PO4)3/rmGO (∼200 nm particles) nanocomposite cathodes display discharge capacities of, respectively, 170 and 186 mA h g−1 at 0.1 C rate and 118 and 135 mA h g−1 at 10 C rate between 3.0 and 4.8 V. The higher discharge capacity and rate capability of Li3V2(PO4)3/rmGO compared to Li3V2(PO4)3/rGO are ascribed mainly to the smaller particle size of Li3V2(PO4)3 and the tight contact between the Li3V2(PO4)3 nanoparticles and the rmGO sheets. The tight contact enables fast electron transport through the underlying rmGO sheets to Li3V2(PO4)3 nanoparticles. [Copyright &y& Elsevier]

Abstract: The design of predictive, electrochemical, Li-ion battery models and the use of model-order reduction techniques to extract low-order models enables researchers to address problems related to model-based control, estimation, aging, and life-cycle prediction. This paper presents a novel approach to the design and parametrization of a reduced-order model characterizing the dynamic voltage response of a Li-ion cell. The model is based on the assumption of uniform active material utilization and includes prediction of the ionic concentration and potential dynamics in the liquid phase, which significantly affects the voltage response for high currents. A model-order reduction procedure based on the Pade approximation method is used to reduce the partial differential equation model to a low-order system of ordinary differential equations. Systematic methods are proposed to identify the electrochemical parameters that govern power and capacity prediction, as well as their temperature dependence. The procedure is based on carefully designed experiments that isolate the influence of small groups of parameters on the voltage output, utilizing complete cell data for model identification almost entirely in place of half-cell characterization. Finally, an extensive validation with experimental data illustrates the ability of the model to accurately predict the cell voltage. [Copyright &y& Elsevier]

The presented work describes a process for producing a mixed-conducting SOFC cermet anode through the in situ reduction of a ternary oxide. A porous nickel tungstenate (NiWO4) was screen-printed and bonded onto an yttrium-stabilized zirconia (YSZ) electrolyte-supported SOFC by treatment at 1000 °C for 1 h. An (La,Sr)MnO3/Ce0.9Gd0.1O2(LSM/GDC) was utilized as the cathode with the NiWO4 acting as the anode for the SOFC. The ∼1-cm diameter fuel cell with a ∼100-μm thick YSZ electrolyte was tested in H2 fuel at 800 °C. During the insertion of the H2 fuel, the NiWO4 was reduced to form a Ni/WO x cermet composite that consisted of a fine mixture of Ni-nanoparticles dispersed over the porous WO x support structure. A maximum power density of ∼104 mW cm−2 was attained for the reduced NiWO4 anode, even with an un-optimized and dense microstructure, on an electrolyte-supported cell. The power density was increased to ∼165 mW cm−2 with the incorporation of GDC powder into the NiWO4 anode. The same NiWO4/GDC composite was tested within a fuel stream of H2 containing 10 ppm PH3. The cell's degradation rate was 0.006 V h−1 for 5 h at 750 °C, which is similar to that observed for conventional Ni/YSZ cermets. [ABSTRACT FROM AUTHOR]

Abstract: A reduction in Ohmic, activation and concentration-polarization losses is of paramount importance in improving the efficiency of solid oxide fuel cells, proton-exchange-membrane fuel cells, and molten-carbonate fuel cells. Efficient measurements of gas diffusivities at the operating conditions of fuel cells allow concentration polarization losses of these fuel cells to be reliably evaluated. To enhance the applicability of solid oxide fuel cells, tremendous work on the development of gas diffusion models and gas diffusivity measurement techniques have been done to pre-evaluate the concentration polarization losses of fuel cells. This review focuses on the recent advancement of gas diffusion models and diffusivity measurement techniques of solid oxide fuel cells. The review seeks to provide an insightful guidance for designing high-performance solid oxide fuel cell electrodes with efficient thickness, porosity, among other parameters. [Copyright &y& Elsevier]

Abstract: The commercialization of lithium–sulfur batteries is hindered by serious capacity fading that mainly results from the irreversible oxidation of sulfur active material during cycling, but so far the underlying oxidation mechanism still remains unclear. The research results reveal that the most practical solvent DOL and DME are not stable and large amount of degradation products with -OLi edge groups become the oxygen source. The shuttle phenomenon is an important reason leading to the irreversible oxidation of sulfur active material, which results from series chemical reductions of lithium polysulfide, and they keep charge conservation by their selves, but prolong the charge process and lead to the overcharging. In charge process, the low speed reactions of long-chain lithium polysulfide oxidized to Li x SO y species exist in the electrolyte, which are indistinctly in the systems without overcharging. As the shuttle phenomenon prolongs the charge process, the irreversible oxidation reactions become distinctly, and the Li x SO y species are detectable. The overcharging capacity could be explained as a reversible part and an irreversible part. The reversible capacity is from the cathode active material oxidized to long-chain lithium polysulfide and elemental sulfur, and the irreversible capacity is from the long-chain lithium polysulfide oxidized to Li x SO y species. [Copyright &y& Elsevier]

Abstract: Three kinds of reduced graphene oxides are prepared by hydrothermal reduction under different pH conditions and their pseudocapacitive performances are evaluated using full-cell supercapacitor devices. The pH values are found to have great influence on the performance of the supercapacitors, achieving the highest specific capacitance value reported for hydrothermal reduced graphene oxide supercapacitors. Acidic and neutral media yield reduced graphene oxides with more oxygen-functional groups and lower surface areas but with broader pore size distributions than those in basic medium. The graphene produced in the basic solution (nitrogen-doped graphene) presents mainly electrochemical double layer (ECDL) behavior with specific capacitance of 185 F g−1, while the graphene produced under neutral or acidic conditions show both ECDL and pseudocapacitive behavior with specific capacitance of 225 F g−1 (acidic) and 230 F g−1 (neutral), respectively, at a constant current density of 1 A g−1. The influence of pH on cycling performance and electrochemical impedance of the supercapacitive devices is also presented. [Copyright &y& Elsevier]

Abstract: Silicon monoxide (SiO) has a high-expected capacity and long cycle performance, but the first cycle''s charge–discharge efficiency was lower than that of a conventional anode material. Recently, we have reported that the irreversible capacity was able to be suppressed based on the crystallinity of SiO. In order to decrease the oxygen defect and improve the crystallinity of SiO, Fe2O3 was reacted with SiO as an oxygen source then heat-treated at 800 °C. When the sample of the mixed SiO and Fe2O3 at a molar ratio of 1:0.2 was heated, Fe2SiO4 (fayalite) with the Pbnm olivine structure was uniformly formed on the SiO surface. It was confirmed that the efficiency of the first cycle''s charge–discharge capacity improved in comparison to the conventional SiO. [Copyright &y& Elsevier]

Abstract: Alloyed Pd m Au nanoparticles (m refers to the atomic Pd/Au ratio), prepared through the co-reduction of K2PdCl4 and HAuCl4 precursors in aqueous solutions, are employed as the catalysts for ethanol electro-oxidation reaction (EOR) in alkaline electrolyte. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) are used to characterize the morphology and confirm the alloy structure of the samples. Cyclic voltammetry (CV) and chronoamperometry (CA) results indicate that the addition of Au to Pd can significantly improve the catalytic activity of Pd toward EOR and the improvement is strongly dependent on the composition of the catalysts. Pd1.0Au/C is identified as the most efficient catalyst since it produces the highest catalytic activity and long-term stability. The mass-specific activity (MSA) and intrinsic activity (IA) data of Pd1.0Au/C is 1.45 mA μg−1 Pd+Au and 80.2 A m−2 Pd, which is found to be 2.3 and 11.3 times that of the Pd/C catalyst, respectively. These findings clearly suggest that the proximity and relative amount of Au and Pd on the surface of the nanoparticles (NPs) are crucial for the improvement of Pd catalysis, which would have important implications for designed preparation of bimetallic catalysts for the direct alcohol fuel cells. [Copyright &y& Elsevier]

Abstract: High crystallinity binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes (bi-FePc/MWNT), was synthesized. Transmission electron microscopy (TEM) confirms that the crystalline bi-FePc forms a uniform coating on the carbon nanotubes with a thickness of about 20 nm. The plane of the macrocyle is perpendicular to the surface of the nanotube and the stacking axis of the bi-FePc molecules, which is the direction of high electrical conductivity, is found to be parallel to the substrate. The bi-FePc/MWNT show activity of 1.43 mA cm−2 at 0.66 V versus NHE indicating good activity and the current is stable for 14 h as electrocatalyst in oxygen reduction reactions (ORR) indicating good stability; the oxygen reduction current does not change in the presence of methanol showing the binuclear iron phthalocyanine coated onto multi-walled carbon nanotubes specifically catalyzes oxygen reduction and not methanol oxidation. [Copyright &y& Elsevier]

Abstract: We demonstrate the effects of reduced cation ordering on the electrochemical properties of LiNi0.5Mn1.5O4. LiNi0.5Mn1.5O4 is treated with nitric acid to reduce the degree of cation ordering. Nitric acid treatment induces partial oxidation of Ni2+ to Ni3+ as confirmed by X-ray photoelectron spectroscopy (XPS). Thanks to this oxidation, the 16d octahedral site in LiNi0.5Mn1.5O4 is quite void of cation ordering and its structure is partially changed to more disordered spinel engaged in Fd3m. This structural change is accompanied by significantly enhanced electrochemical performances in rate capability as well as cyclic retention. Actually, nitric acid treated LiNi0.5Mn1.5O4 can deliver about 87% of the initial capacity (129 mAh g−1) even after 100 cycles even at 55 °C. [Copyright &y& Elsevier]

Abstract: Nitrogen-doped reduced graphene oxide (N-RGO) and reduced graphene oxide (RGO) have been synthesized by microwave-assisted hydrothermal method to discern the actual contribution of nitrogen-containing functional groups on the specific capacitance (C S,T) in acidic and alkaline electrolytes. Material characterization reveals similar porosity, electrolyte-accessible surface area, element composition, and graphitic crystallinity between N-RGO and RGO except the difference in the nitrogen content. In 1 M H2SO4, additional pseudocapacitance provided by pyridinic-N and pyrrolic-N/pyridone-N is clearly observed at the potential negative to 0.6 V (vs. RHE) while this contribution in pseudocapacitance diminishes in 1 M KOH due to the lack of proton in the electrolyte for these basic functional groups to undergo redox reactions. The double-layer capacitance of N-RGO in 1 M H2SO4 in higher than that in 1 M KOH owing to the presence of N-containing functional groups which increase the electronic charge density of graphene and favor proton adsorption in the acidic electrolyte. The contribution of nitrogen-containing functional groups on C S,T in acidic media is more pronounced than that in the alkaline electrolyte. This finding is crucial for the future application of N-doped carbons in supercapacitors to achieve full utilization. [Copyright &y& Elsevier]

Abstract: Carbon supported Ru nanoparticles (Ru/C) prepared by liquid phase reduction of RuCl3 by NaBH4 under pH control were applied to anode electrocatalysts of alkaline anion exchange membrane fuel cell (AAEMFC) using hydrogen as fuel. Ru nanoparticles having ca. 3 nm diameter represented higher cell performance than not only Ru/C having large particle size (ca. 11 nm) but also a commercially available Pt/C catalyst. The cell performance of Ru/C increased with the cycle of fuel cell testing. X-ray absorption fine structure spectroscopy analysis indicated that Ru species was reduced during fuel cell testing. Thus, Ru metal can act as highly active site for hydrogen adsorption and oxidation in AAEMFC. The cell testing was also performed using Rh/C, Pd/C, and Ag/C to show that Ru/C was the most active anode catalyst for AAEMFC. [Copyright &y& Elsevier]

Abstract: Na3V2(PO4)3 of the rhombohedral NASICON structure has been prepared via solid state carbothermal reduction reaction assisted by mechanochemical activation. As a cathode material for hybrid lithium ion batteries, Na3V2(PO4)3 exhibits an initial specific discharge capacity of 114.2 mAh g−1 in the voltage range between 2.5 V and 4.6 V, with a long discharge plateau near 3.7 V versus lithium metal. Approximately 3% of the discharge specific capacity is lost over the first 3 cycles at a current rate of 0.1 C. Then, the capacity appears to stabilize with the discharge specific capacity retention of 97.4% over the following 97 cycles. The material also exhibits good rate performance. Reversible capacities of 107.0 mAh g−1 at a 1 C rate, 100.5 mAh g−1 at 5 C and 84.4 mAh g−1 at 10 C have been obtained. The preliminary results prove that Na3V2(PO4)3 is a new promising material for hybrid lithium ion batteries. [Copyright &y& Elsevier]

Abstract: Co@Pt/C core–shell catalysts are synthesized by a two-step chemical reduction method followed by the heat treatment in H2 and N2 mixture. High Resolution (HR-TEM), EDX (Energy-dispersive X-ray spectroscopy) and in-situ X-ray diffraction (XRD) techniques are used to characterize the nano-structured catalysts. The results show that the core–shell structure of Co@Pt/C is formed and the average particle size is about 3 nm. From the result of the in-situ XRD, it is found that the heat treatment favors for the formation of crystalline structure and the proper particle size of catalyst. The in-situ XRD detection also helps find the optimized heat treatment temperature. The linear sweep voltammetry (LSV) result reveals that the Co@Pt (1:3)/C (reduced) catalyst exhibits the best catalytic activity toward oxygen reduction reaction (ORR). A 130 h life time test for the single cell, in which the membrane electrode assembly (MEA) using Co@Pt (1:3)/C (reduced) as the cathode catalyst, is operated to evaluate the durability. The results of the test show that the formation of the core–shell structure of Co@Pt/C catalyst is favorable to improve the stability and durability. [Copyright &y& Elsevier]

Abstract: Reduced graphene oxide (r-GO) paper is easily synthesized by a flame-induced reduction of graphene oxide (GO) paper under ambient conditions. The X-ray diffraction and X-ray photoelectron spectroscope results confirm the effectivity of the flame-induced reduction. The resulting r-GO paper has a high surface area of 274.9 m2 g−1 and contains a certain amount of oxygen-containing groups. Electrochemical behaviors of the electrode built with the r-GO paper are investigated in two kinds of electrolytes, 2 M KOH aqueous solution and 1 M Et4NBF4-acetonitrile solution, respectively. The results show that the high values of the specific capacitance for the r-GO can be obtained in both electrolytes, which reach 212 and 160 F g−1 at the same current density of 1 A g−1 respectively. Also, the r-GO-based electrode and supercapacitor exhibits stable cycling performance. The good capacitive performances in KOH aqueous electrolyte are due to the high surface area and the remaining oxygen containing groups of the r-GO paper. [Copyright &y& Elsevier]

Abstract: A novel 3D nanostructure consisting of Ni(OH)2 nanoparticles, carbon nanotubes (CNTs), and reduced graphene oxide with an extremely high electrocapacitance is described. The nanostructure consists of CNTs with embedded Ni(OH)2 nanoparticles as pillars for reduced graphene oxide sheets. Electrochemical results show that the composite displays specific capacitances as high as 1235 and 780 F g−1 at current densities of 1 and of 20 A g−1, respectively. In addition, the composite retains 80% of its original capacity after 500 cycles at a discharge current density of 10 A g−1. This 3D pseudocapacitor electrode has a number of important features, such as fast ion and electron transfer, easy access of pseudoactive species and efficient utilization, and excellent reversibility of Ni(OH)2 nanoparticles. [Copyright &y& Elsevier]

Abstract: The detailed isothermal electrochemical model for a lithium ion cell comprises of 10 coupled partial differential equations (PDEs). It is computationally intensive to use this model for detailed parameter estimation, battery packs, battery management system algorithms, calendar or cycle life predictions etc. This work describes a reduced order model framework, which reduces the detailed model PDEs, to a manageable set of ordinary differential equations (ODEs), which can be used for the above applications. Volume averaging PDEs yield ODEs. Hence volume averaging is the basic method used for model reduction. The gradient or profile information lost on volume averaging is recovered through profile based approximations. For the lowest order reduced order model (ROM), a uniform reaction rate, quadratic electrolyte concentrations and quartic solid phase concentrations are assumed. In this ROM only 5 linear ODEs are solved, and the rest are nonlinear algebraic evaluations. When compared with the detailed electrochemical model of a lithium ion cell, this ROM gives negligible error at nominal currents and a maximum error of about 3% at high currents, for a typical commercial cell. [Copyright &y& Elsevier]

Abstract: Graphene nanosheets (GNS) wrapped SnCo alloy nanoparticles are prepared by a chemical reduction method on an ice water bath. SnCo nanoparticles are dispersed uniformly on GNS and their particle sizes are around 8-12 nm, which are substantially smaller than the pristine SnCo particles (∼80-180 nm) prepared in the absence of GNS. The GNS-SnCo composite is fabricated as an anode material for lithium ion batteries. It shows a distinguished higher-than-theoretical capacity of 1117 mAh g−1 at 72 mA g−1, which is larger than bare GNS (727 mAh g−1) or Sn-Co particles (599 mAh g−1). Moreover, the GNS-SnCo composite shows a good rate performance at a large current of 720 mA g−1. A high capacity of 922 mAh g−1 is retained with more stable cycle life than that at a small current. These improved cycling performances are attributed to the complimentary effect of three elements. The mechanical stability of Sn upon cycling is improved by the presence of robust and electrically conductive GNS and the alleviated function of inactive cobalt element. The agglomeration of GNS is also hindered by the spacing effect of SnCo nanoparticles among neighboring GNS materials. [Copyright &y& Elsevier]

Abstract: A facile approach to the surface reduced graphene oxide (rGO) modification of micro-nano structured vanadium oxides composites are developed as cathode materials of lithium ions batteries (LIBs) and supercapacitors (SCPs) for the first time. The as-prepared V2O5–rGO and VO2–rGO composites exhibit remarkably enhanced cycling performance when being used as cathode materials in LIBs and SCPs, respectively. The uniform coating of graphene around the surface of vanadium oxides ensures good close electrical contact, therefore higher specific capacity and enhanced cycling performance than pure VO2 and V2O5 electrodes. Meanwhile, the cycling performance enhancement and capacity decay mechanism are presented, which is not only important to design electrode materials in LIBs and SCPs, but also extendable to the design and fabrication of other functional materials for energy storage and transfer systems. [Copyright &y& Elsevier]

Abstract: This paper reports on the application of hydroxide ion conducting layered double hydroxides (LDHs) to the catalyst layer in an alkaline fuel cell for the improvement of the oxygen reduction reaction (ORR) at the triple phase boundary (TPB) in the catalyst layer. Ni–Al LDH intercalated with (Ni–Al LDH) and Mg–Al LDH were used in this study. Ni–Al LDH showed higher ionic conductivity than Mg–Al LDH under R.H. of 80%. The catalyst layers with and without hydroxide ion conducting LDHs was prepared, and a half-cell using the prepared catalyst layers was fabricated. The addition of LDHs to the catalyst layer increased the reduction current for ORR, indicating that hydroxide ion conducting LDHs introduced OH− conducting paths and increased TPB region within the catalyst layer. Above all, the addition of Ni–Al LDH to the catalyst layer more effectively increased the reduction current for ORR than the addition of Mg–Al LDH. The performance of the alkaline-type direct ethanol fuel cell was also improved. These experimental results indicate that high hydroxide ion conducting Ni–Al LDH effectively increased TPB region within the catalyst layer. [Copyright &y& Elsevier]

Abstract: The effects and affecting mechanisms of carbon dioxide on oxygen reduction reactions on the La0.6Sr0.4CoO3−δ (LSC) and La0.8Sr0.2MnO3+δ (LSM) cathodes have been investigated. The presence of CO2 in O2 flow reduces the LSC and LSM cell performance and increases polarization resistance. CO2 impedes oxygen dissociative adsorption on the LSC cathode, whereas CO2 inhibits dissociation of adsorbed oxygen molecule or diffusion of O-species on the LSM cathode. CO2 adsorption on the LSC cathode obeys Temkin model in 550–650 °C and Freundlich model in 700–800 °C. Different CO2 adsorption behaviors are ascribed to the change in LSC structure and the change in oxygen reduction mechanism. CO2 adsorption on the LSM cathode obeys Freundlich model in 650–800 °C. The differences in the effects and affecting mechanisms of CO2 on LSM and LSC are related to their differences in composition and structure. [Copyright &y& Elsevier]

Abstract: Composite Pd-based electrocatalysts consisting of a surface layer of Pt (5% wt.) supported on a core Pd3Co1 alloy were prepared. Two preparation approaches were investigated. One consisting of a single-step reduction procedure; in the second method, preparation of the PdCo alloy and deposition of a Pt overlayer occurred in two distinct steps. The catalyst prepared by a one-step process showed oxidised Pt species on the surface even if characterized by a smaller crystallite size with respect to the two-step Pd-based catalyst (4 nm vs. 6 nm). Moreover, the two-step process showed an enrichment of Pt on the surface and a smaller content of Co in the outermost layers. The enhanced surface characteristics of the two-step Pd catalyst resulted in a better performance. At 80 °C, the mass activity was lower than a Pt3Co1 alloy catalyst with the same crystallographic structure. Interestingly, the composite PtPdCo catalyst showed a significant increase of performance as the temperature was increased to 110 °C whereas the Pt3Co1 showed a decrease due to a prevailing effect of ionomer dry-out in the catalytic layer. The composite catalyst appeared sufficiently stable after 104 electrochemical cycles between 0.6 and 0.9 V at 110 °C and 33% R.H. [Copyright &y& Elsevier]

Abstract: The electrocatalytic activity for the oxygen reduction reaction of nickel-doped MnO x nanoparticles, dispersed onto different carbon powders (M1000, MM225 and E350) is studied in alkaline media in the presence of borohydride ions. Differential electrochemical mass spectrometry (DEMS) is used to quantify the H2 yields coming from the borohydride hydrolysis as a function of the electrode potential. The polarization results show that materials containing Ni segregate phases present significant Faradaic currents for the borohydride oxidation, while the on-line DEMS results clearly evidence the production of H2. For these electrocatalysts, the presence of BH4 − induces a decrease of the overall ORR activity, and this is assigned, into a large extent, to a superposition of the ORR reduction currents with the currents related to the direct borohydride oxidation. This effect is far more pronounced for the electrocatalyst dispersed onto the E350 carbon. On the contrary, materials dispersed onto M1000 carbon and without Ni segregated phases seem tolerant to the presence of BH4 − ions. Therefore, these materials may be an alternative to be used as cathode electrocatalysts of direct borohydride fuel cells. [Copyright &y& Elsevier]

Abstract: WO3 nanobars with the length of 10–50nm and the width of 3–6nm on carbon (C-WO3) are synthesized through an ionic exchange route to locally anchor the metatungstate ions (W7O24 6 −). The structures, morphologies and catalytic performance of the as-synthesized nanomaterials are characterized by various physical and electrochemical methods. The results indicate that Pt nanoparticles supporting on C-WO3 (Pt/C-WO3) are highly active and stable as cathode electrocatalyst for fuel cells. On one hand, a mass activity of 174.6mAmg−1 Pt at 0.9V is obtained for oxygen reduction reaction (ORR), which is much higher than that on commercial Pt/C electrocatalyst (98.6mAmg−1 Pt). On the other hand, Pt/C-WO3 electrocatalyst shows excellent electrochemical stability than Pt/C. The origin of these improvements in the catalytic activity can be attributed to the synergistic or promotion effect of WO3 on Pt. The improvement in the electrochemical stability is due to and also explains the stronger interaction force between Pt and WO3 than that between Pt and C. The present method is simple and effective, which can be readily scale up for the production of other nanomaterials as well as WO3. [Copyright &y& Elsevier]

Abstract: The catalytic activity of electrochemically dealloyed PdCu3 thin films for oxygen reduction reaction (ORR) in acidic media has been studied by using a rotating disk electrode (RDE). The dealloyed PdCu3 thin films show a ∼2.0 fold increase in the specific oxygen reduction activity over pure Pd thin films. The structure of electrochemically dealloyed PdCu3 thin films has been investigated at an atomic scale by synchrotron-based anomalous X-ray diffraction (AXRD). AXRD reveals that a Pd enriched surface layer is formed in the dealloyed film and a compressive lattice strain exists in this Pd surface layer. The enhanced catalytic activity of dealloyed Pd–Cu films for the ORR is primarily due to the compressive strain in the surface layer. We compare the structure–composition–catalytic activity relationships in dealloyed Pd–Cu thin films to related results on dealloyed Pt–Cu thin films. These studies show that dealloying and the resulting structure and the ORR activity are dependent on the nature of the noble component of alloy. [Copyright &y& Elsevier]

Abstract: Carbothermal reduction using sucrose was applied to Fe- and/or Ti-substituted Li2MnO3 positive electrode materials to improve their poor initial cycle efficiency (<60%) of 2.0–4.8 V. The initial cycle efficiency was improved from 53% to 68% for Li1+x (Ti0.5Mn0.5)1−x O2, 63%–72% for Li1+x (Fe0.3Mn0.7)1−x O2, or 62%–78% for Li1+x (Fe0.2Ti0.2Mn0.6)1−x O2 by application of the carbothermal reduction process. All samples belong to 3.2 V class positive electrode material with high initial discharge capacity higher than 220 mAh g−1. The shape change of discharge curve with cycle progression was suppressed for all reduced samples. The compositional, transition metal valence state, and structural and powder property changes occurring before and after carbothermal reduction processing were examined to construct the material design concept of attractive Li2MnO3-based positive electrode candidates using only naturally abundant and cheap elements (Ti and Fe) as constituent metals. [Copyright &y& Elsevier]

Abstract: In this paper we report the use of both ultrasonic spray pyrolysis and microwave-assisted polyol reduction methods to synthesize Nb-doped TiO2/carbon (25 wt% Nb0.07Ti0.93O2/75 wt% carbon) composite supports and Pt0.62Pd0.38 alloy catalysts, respectively. The physicochemical properties of the synthesized supports and their Pt0.62Pd0.38 supported catalysts are evaluated using several methods including XRD, TEM, BET surface area analysis, TGA, as well as ICP-MS elemental analysis. The electronic conductivities and thermal/chemical stabilities of the supports are also evaluated with respect to their possible use as catalyst supports. Electrochemical measurements for oxygen reduction activity of the Pt0.62Pd0.38 alloy catalysts supported on oxide/carbon composites are also carried out in order to check their suitability for possible PEM fuel cell applications. The results show that 20wt%Pt0.62Pd0.38/25 wt%(Nb0.07Ti0.93O2)-75 wt%C catalysts exhibit enhanced mass activities compared to those of commercially available 48wt% Pt/C and home-made 20wt% Pt62Pd38/C catalysts. [Copyright &y& Elsevier]

Abstract: Tridodecylmethylammonium chloride (TDMAC) functionalized reduced graphene oxide (TDMAC-RGO) has synthesized by a simple physicochemical process. The resultant functionalized graphene imparts electrocatalytic activity as metal- free catalysts for the oxygen reduction reaction (ORR) in fuel cells (FCs), with long-term operational stability, and tolerance to methanol and ethanol via a four-electron pathway in alkaline FCs. The ORR activities have systematically investigated by cyclic voltammetry (CV) and rotating ring disk electrode (RRDE) techniques. The results show that the TDMAC-RGO demonstrates excellent catalytic activity for oxygen reduction. Raman and X-ray photoelectron spectroscopic (XPS) measurements indicate charge transfer from the graphene sheets to the TDMAC via intermolecular charge-transfer. TDMAC-RGO catalysts are low-cost, free of metal and costly polymers, and are an efficient approach to FC applications. [Copyright &y& Elsevier]

Abstract: A Ni nanowire array (NiNWA) supported three-dimensional flower-like Pd nano-electrocatalyst with high electrocatalytic performance for the electrooxidation of ethanol in alkaline media has been fabricated by borohydride hydrothermal reduction method. This novel hybrid NiNWA/PdNF (nanoflowers) electrocatalyst exhibits large electrochemically active surface area (EASA, 45m2 g−1(Pd)), excellent electrocatalytic activity (765mAmg−1(Pd)), and high level of the poisoning tolerance (I f /I b =1.2) to the carbonaceous oxidative intermediates for the electrooxidation reaction in alkaline media. In addition, the electrochemical stability of NiNWA/PdNF is significantly higher than that of NiNWA/PdNP (nanoparticles) electrocatalyst, as evidenced by chronoamperometry experiments in which the electrooxidation current of nanoflowers is controlled by the diffusion transport of ethanol species rather than the carbonaceous poisoning. This high electrocatalytic activity can be attributed to the more open structure with higher electrochemically active sites and shape of Pd nanoflowers. This is further enhanced by the core support NiNWA with a very large surface area and the open interspaces that ensure easy alcohol access even to remote active sites for fast ion adsorption/desorption. [Copyright &y& Elsevier]

Abstract: Crystalline hausmannite nanocrystals/reduced graphene oxide composites (denoted as Mn3O4/RGO) are synthesized by means of the microwave-assisted hydrothermal synthesis (MAHS) route for the application of symmetric and asymmetric supercapacitors. Effects of the Mn3O4 content on the microstructure and electrochemical performances of nanocomposites are systematically investigated. The morphology and crystalline structure of composites are examined by scanning electron microscopic (SEM) and X-ray diffraction (XRD) analyses. Thermogravimetric analysis (TGA) is used to determine the mass content of RGO in the Mn3O4/RGO composites. The results indicate that the composite with about 82.4 weight percents (wt%) Mn3O4 (denoted as GMn80) shows the largest total specific capacitance (∼193 F g−1), which is employed for the tests of supercapacitors of both symmetric and asymmetric types. An aqueous asymmetric supercapacitor, consisting of a GMn80 cathode and an N-doped RGO anode (reduced from a GO-NH4OH solution through the MAHS method), with a cell voltage of 2 V is demonstrated in this work, which shows the device energy and power densities of 11.11 Wh kg−1 and 23.5 kW kg−1, respectively. [Copyright &y& Elsevier]

Abstract: Reduced graphene oxide (RGO) is synthesized and added in situ into the reaction system of polyaniline (PANI) electrodeposition using activated carbon cloth (ACC) as the substrate. The effect of RGO on the morphology, structure, and electrochemical properties of the ACC/PANI composite is investigated. A more compact and uniform layer of PANI film is observed via scanning electronic microscopy after the addition of RGO. Raman spectroscopy shows that RGO has been simultaneously deposited with PANI onto the surface of ACC. X-ray photoelectron spectroscopy reveals that the sample with RGO exhibits a higher sulfur-to-nitrogen ratio. The reversibility of the redox reaction of PANI is improved, as confirmed via cyclic voltammetry. The electrochemical impedance spectroscopy data shows that the introduction of RGO lowers the charge-transfer resistance of ACC/PANI, meanwhile, improves the coverage percentage of PANI on the ACC surface to a significant extent, primarily because of the interactions between RGO, ACC, and PANI. The as-prepared composite with RGO shows improved rate performance and cyclability as a supercapacitor electrode. [Copyright &y& Elsevier]

Abstract: It is accepted that the reduction of iodine species in non-aqueous solvents occurs through one-electron or two-electron processes below roughly 3.5 V vs. Li/Li+. In some iodine solutions, the molecular complexation of iodine with the organic solvent proceeded via a charge–transfer interaction. Reduction of iodine in non-aqueous solvents having S:glyph name="dbnd" />O groups, as well as interactions of iodine molecules with these solvents, were studied. Iodine molecules associated with dimethyl sulfoxide (DMSO), tetramethylene sulfoxide (TMSO), and trimethyl phosphate (TMP) showed anomalous reduction above+1.0 V vs. NHE. We demonstrated the operation of lithium–iodine batteries using DMSO, TMSO and TMP near 4.0 V vs. Li/Li+. [Copyright &y& Elsevier]

Abstract: Li3V2(PO4)3 nanocrystals (5–8 nm) embedded in a nanoporous carbon matrix attached onto reduced graphene oxide nanosheets (LVP-NC@NPCM@rGO) are synthesized by a facile approach. The rGO sheets not only form the interconnected conducting scaffold to enhance the charge transfer but also act as the heterogeneous nucleation site to facilitate the growth of nanograins of LVP. The nanoporous carbon acts as the nanocontainer to enhance the electrolyte/active material interaction and also inhibit the grain growth of Li3V2(PO4)3. This leads to the fast kinetics of the Li ion transfer and the excellent cathode performance, especially at high current densities. Binder-free cathodes can be prepared based such LVP-NC@NPCM@rGO sample, which shows high specific capacities, stable cyclabilities and excellent rate capabilities in the voltage ranges of 3.0–4.3 and 3.0–4.8 V. [Copyright &y& Elsevier]

Abstract: A viscoelastic-plastic constitutive model is developed to characterize the time-dependent mechanical response of perfluorosulphonic acid (PFSA) membranes. This model is then used in finite element simulations of a representative fuel cell unit, (consisting of electrodes, gas diffusion layer and bipolar plates) subjected to standardized relative humidity (RH) cycling test conditions. The effects of hold times at constant RH, the feed rate of humidified air and sorption rate of water into the membrane on the stress response are investigated. While the longer hold times at high and low humidity lead to considerable redistribution of the stresses, the lower feed and sorption rates were found to reduce the overall stress levels in the membrane. The redistribution and reduction in stress magnitudes along with inelastic deformation during hydration eventually lead to development of residual tensile stresses after dehydration. Simulations indicate that these tensile stresses can be on the order of 9–10 MPa which may lead to mechanical degradation of the membrane. The simulation results show that time-dependent properties can have a significant effect on the in-plane stress response of the membrane. [Copyright &y& Elsevier]