Many industrial catalysts are composed of metal particles supported on metal oxides (MMO). It is known that the catalytic activity of MMO materials is governed by metal and metal oxide interactions (MMOI), but how to optimize MMO systems via manipulation of MMOI remains unclear, due primarily to the ambiguous nature of MMOI. Herein, we develop a Pt/NbOx/C system with tunable structural and electronic properties via a modified arc plasma deposition method. We unravel the nature of MMOI by characterizing this system under reactive conditions utilizing combined electrochemical, microscopy, and in situ spectroscopy. We show that Pt interacts with the Nb in unsaturated NbOx owing to the oxygen deficiency in the MMO interface, whereas Pt interacts with the O in nearly saturated NbOx, and further interacts with Nb when the oxygen atoms penetrate into the Pt cluster at elevated potentials. While the Pt–Nb interactions do not benefit the inherent activity of Pt toward oxygen reduction reaction (ORR), the Pt–O interactions improve the ORR activity by shortening the Pt–Pt bond distance. Pt donates electrons to NbOx in both Pt–Nb and Pt–O cases. The resultant electron eficiency stabilizes low-coordinated Pt sites, hereby stabilizing small Pt particles. This determines the two characteristic features of MMO systems: dispersion of small metal particles and high catalytic durability. These findings contribute to our understandings of MMO catalytic systems.

Flexible polypyrrole (PPy) films with highly ordered structures were fabricated by a novel vapor phase polymerization (VPP) process and used as the anode material in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The PPy films demonstrate excellent rate performance and cycling stability. At a charge/discharge rate of 1 C, the reversible capacities of the PPy film anode reach 284.9 and 177.4 mAh g–1 in LIBs and SIBs, respectively. Even at a charge/discharge rate of 20 C, the reversible capacity of the PPy film anode retains 54.0% and 52.9% of the capacity of 1 C in LIBs and SIBs, respectively. After 1000 electrochemical cycles at a rate of 10 C, there is no obvious capacity fading. The molecular structure and electrochemical behaviors of Li- and Na-ion doping and dedoping in the PPy films are investigated by XPS and ex situ XRD. It is believed that the PPy film electrodes in the overoxidized state can be reversibly charged and discharged through the doping and dedoping of lithium or sodium ions. Because of the self-adaptation of the doped ions, the ordered pyrrolic chain structure can realize a fast charge/discharge process. This result may substantially contribute to the progress of research into flexible polymer electrodes in various types of batteries.Keywords: flexible; free-standing anode; Li-ion battery; Na-ion battery; orderly structure; overoxidized; polypyrrole film; vapor phase polymerization;

Accurate modeling of open-circuit-voltage (OCV) plays important roles both in state-of-charge (SOC) estimation and state-of-health (SOH) monitoring for lithium-ion batteries (LIBs). Monotonicity violation in OCV model would lead to inaccurate SOC estimation and ineffective of incremental capacity analysis (ICA) for SOH monitoring. In this study, first-order derivative of OCV, with respect to SOC is introduced to theoretically ensure the satisfaction of monotonicity and a nonlinear semi-infinite programming (NSIP) problem is constructed to parameter estimation. A global optimization approach via restriction of the right-hand side is used to efficiently and globally optimize the NSIP. Both fitting and ICA results demonstrate the effectiveness of the proposed method. Moreover, in comparison to the traditional polynomial and sigmoid models, the NSIP polynomial model is the best choice for performing further SOC estimation and SOH monitoring. The results thus indicate that a NSIP framework for embedding prior knowledge not only provides a promising approach to automatically capture OCV-SOC monotonicity constraint in LIBs, but also serves as a universal methodology for process modeling with the requirements of embedding derivative constraints.

•Rubidium and cesium ions are used as electrolyte additives for sodium-ion battery.•Rb+ and Cs+ ions modify the solid electrolyte interphase.•The performance of Na/HC(hard carbon) is improved by addition of Rb+ and Cs+ ions.In this work, rubidium and cesium ions are studied as electrolyte additives for sodium-ion batteries. It is shown that adding small amount of Rb+ and Cs+ into the electrolyte significantly modifies the chemical composition of solid electrolyte interphase (SEI) on hard carbon (HC) surfaces, which results in a significant increase in the ionic conductivity and stability of the SEI. The results of this work show that a 0.05 M addition in the form of MPF6 (M = Rb or Cs) can increase the capacity retention of the Na/HC cells to 95.3% and 97.1% by the Rb+ and Cs+ ions, respectively, from 80.6% of the control cell after 100 cycles.Download high-res image (131KB)Download full-size image

•Fe, N, and S functionalized carbon electrocatalyst for ORR.•Effective suppression of the formation of the unstable species.•Superior catalytic activity to Pt/C catalyst toward ORR in the fuel cell operating range.•Better durability and methanol tolerance than Pt/C in alkaline electrolyte.We demonstrate here a Fe, N, and S functionalized carbon (Fe/N/S-C) derived from an iron incorporated and p-toluenesulfonate doped polypyrrole precursor on a carbon support as an efficient catalyst for oxygen reduction reaction (ORR). Such a strategy could effectively suppress the formation of inferior activity metal species and less active oxidized type sulfur species. The as-synthesized Fe/N/S-C catalyst exhibited a highly catalytic activity for ORR which is comparable to the state-of-the-art commercial Pt/C catalyst at low overpotential range while have a better catalytic activity at the fuel cell operation potential range. In addition, this catalyst showed a higher durability and better tolerance to alcohol fuel than Pt/C catalyst.Download high-res image (83KB)Download full-size image

Rechargeable lithium-ion batteries (LIBs) offer the advantages of having great electrical energy storage and increased continuous and pulsed power output capabilities, which enable their applications in grid energy storage and electric vehicles (EVs). For safety, high power and durability considerations, spinel Li4Ti5O12 is one of the most appealing potential candidate as an anode material for power LIBs due to its excellent cycling stability and thermal stability. However, there are still a number of challenges remaining for Li4Ti5O12 battery applications. Herein, an updated overview of the latest advances in Li4Ti5O12 research is provided and key challenges for its future development (i.e., fast-charging, specific capacity, swelling, interface chemistry, matching cathode and electrolyte as well as batteries design and manufacturing) are highlighted.

Prussian blue and its analogues have been intensively studied as potential electrode materials for sodium ion batteries. In this work, a prussian blue sample was prepared by a simple precipitation method and the electrochemical performance of the prussian blue (PB) cathode was investigated at various temperatures and in different voltage ranges. When cycled in the voltage range of 2.0 − 4.0 V vs. Na/Na+, the PB cathode exhibited initial discharge capacities of 135.4 mAh g−1 (55 °C), 128.5 mAh g−1 (25 °C) and 99.2 mAh g−1 (-10 °C) at 10 mA g−1. The PB cathode showed good cycling stability at low temperature, however the cycling capacity degraded remarkably at elevated temperature. CV test indicated that the capacity fade was mainly due to the side reactions on the electrode-electrolyte interface at near 4.0 V vs. Na/Na+. XPS and FTIR analyses revealed several types of compounds formed on the cathode surface which indicated the complexity of the side reactions. Controlling the high cut-off voltage at 3.8 V vs. Na/Na+ significantly improved the cycling stability of the PB electrode. The PB cathode delivered 1C rate reversible capacity of 100.0 mAh g−1 in 2.0 − 3.8 V vs. Na/Na+ with outstanding capacity retention of 98.2% after 300 cycles.

Electrolyte design or functional development is very effective at promoting the performance of sodium-ion batteries, which are attractive for electrochemical energy storage devices due to abundant sodium resources and low cost. This review discusses recent advances on electrolytes for sodium-ion batteries and comprehensive electrolyte design strategies for various materials systems as well as functional applications. The discussion is divided into three electrolyte types: liquid, solid state, and gel state. Liquid electrolytes are further divided into different solvent types, including organic carbonate ester, ether, ionic liquid, and water. Solid-state electrolytes also contain two types: solid polymer and glass–ceramic composite. The challenges and prospects of electrolytes for sodium-ion batteries are discussed as well.

AbstractRealization of the hydrogen economy relies on effective hydrogen production, storage, and utilization. The slow kinetics of hydrogen evolution and oxidation reaction (HER/HOR) in alkaline media limits many practical applications involving hydrogen generation and utilization, and how to overcome this fundamental limitation remains debatable. Here we present a kinetic study of the HOR on representative catalytic systems in alkaline media. Electrochemical measurements show that the HOR rate of Pt-Ru/C and Ru/C systems is decoupled to their hydrogen binding energy (HBE), challenging the current prevailing HBE mechanism. The alternative bifunctional mechanism is verified by combined electrochemical and in situ spectroscopic data, which provide convincing evidence for the presence of hydroxy groups on surface Ru sites in the HOR potential region and its key role in promoting the rate-determining Volmer step. The conclusion presents important references for design and selection of HOR catalysts.

AbstractRealization of the hydrogen economy relies on effective hydrogen production, storage, and utilization. The slow kinetics of hydrogen evolution and oxidation reaction (HER/HOR) in alkaline media limits many practical applications involving hydrogen generation and utilization, and how to overcome this fundamental limitation remains debatable. Here we present a kinetic study of the HOR on representative catalytic systems in alkaline media. Electrochemical measurements show that the HOR rate of Pt-Ru/C and Ru/C systems is decoupled to their hydrogen binding energy (HBE), challenging the current prevailing HBE mechanism. The alternative bifunctional mechanism is verified by combined electrochemical and in situ spectroscopic data, which provide convincing evidence for the presence of hydroxy groups on surface Ru sites in the HOR potential region and its key role in promoting the rate-determining Volmer step. The conclusion presents important references for design and selection of HOR catalysts.

Hierarchically structured carbon coated SnO2 nanoparticles well-anchored on the surface of a CNT (C–SnO2/CNT) material were synthesized by a facile hydrothermal process and subsequent carbonization. The as-obtained C–SnO2/CNT hybrid, when applied as an anode material for lithium ion batteries (LIBs), showed a high reversible capacity up to 1572 mA h g−1 at 200 mA g−1 with a superior rate capability (685 mA h g−1 at 4000 mA g−1). Even after 100 charge/discharge cycles at 1000 mA g−1, a specific capacity of 1100 mA h g−1 can still be maintained. Such impressive electrochemical performance can be mainly attributed to the hierarchical sandwiched structure and strong synergistic effects of the ultrafine SnO2 nanoparticles and the carbon coating, and thus presents this material a promising anode material for LIBs.

A nitrogen-containing carbon (N–C) film was synthesized by pyrolysis of vapor phase polymerized polypyrrole (PPy). This carbon film exhibits excellent rate capability and cyclability as a lithium-ion battery anode. The reversible capacities are 908.4, 825.7, 664.0, 531.6, 415.5 and 325.9 mA h g−1 at 1C, 2C, 5C, 10C, 20C and 40C, respectively.

The emergence of atomically thick nanolayer materials, which feature a short ion diffusion channel and provide more exposed atoms in the electrochemical reactions, offers a promising occasion to optimize the performance of supercapacitors on the atomic level. In this work, a novel monolayer Ni–Co hydroxyl carbonate with an average thickness of 1.07 nm is synthesized via an ordinary one-pot hydrothermal route for the first time. This unique monolayer structure can efficiently rise up the exposed electroactive sites and facilitate the surface dependent electrochemical reaction processes, and thus results in outstanding specific capacitance of 2266 F g–1. Based on this material, an all-solid-state asymmetric supercapacitor is developed adopting alkaline PVA (poly(vinyl alcohol)) gel (PVA/KOH) as electrolyte, which performs remarkable cycling stability (no capacitance fade after 19 000 cycles) together with promising energy density of 50 Wh kg–1 (202 μWh cm–2) and high power density of 8.69 kW kg–1 (35.1 mW cm–2). This as-assembled all-solid-state asymmetric supercapacitor (AASC) holds great potential in the field of portable energy storage devices.Keywords: cycling stability; monolayer; Ni−Co hydroxyl carbonate; solid-state; supercapacitor

Micro-tubular SOFCs have the potential to become light-weight portable auxiliary power units for aircraft or spacecraft. In this work, a novel dual-layer ceramic hollow fiber for a cathode-supported micro-tubular solid oxide fuel cell (MT-SOFC) has been successfully developed via a co-spinning-sintering technique. The green cathode hollow fibers, in dual layer configuration, consisting of a La0.8Sr0.2MnO3−δ (LSM) main layer and a LSM–Y2O3 stabilized ZrO2 (YSZ) functional layer with increased three phase boundary length, are first prepared by co-spinning, which are then sintered at around 1350 °C to allow the creation of sufficient mechanical strength. Other cell components like the electrolyte (YSZ) and anode (NiO + YSZ) are then coated separately. The coated electrolyte film with a thickness of around 27 μm is obtained by co-sintering of YSZ/LSM–YSZ/LSM in a sandwich structure. The porous LSM substrate functions as an oxygen-supplying and current collecting layer. The prepared MT-SOFC, tested with hydrogen as the fuel and air as the oxidant, delivers a maximum power density of up to 475 mW cm−2 at 850 °C, which is much higher than that of a similar cell without a cathode functional layer.

A micro-cubic Prussian blue (PB) without coordinated water is first developed by electron exchange between graphene oxide and PB. The obtained reduced graphene oxide–PB composite exhibited complete redox reactions of the Fe sites and delivered ultrahigh electrochemical performances as well as excellent cycling stability as a cathode in sodium-ion batteries.

•Cobalt-free cathode Nd0.5Sr0.5Fe0.8Cu0.2O3−δ is successfully applied in SC-SOFCs.•Nd0.5Sr0.5Fe0.8Cu0.2O3−δ is phase stable after CO2 treatment.•The performances of the cells are varied under different ratio of CH4 to O2.•Nd0.5Sr0.5Fe0.8Cu0.2O3−δ-SDC is a promising cathode material in SC-SOFCs.As a candidate of cathode material of single-chamber solid oxide fuel cell (SC-SOFC), cobalt-free mixed ionic electronic conductor (MIEC) Nd0.5Sr0.5Fe0.8Cu0.2O3−δ (NSFCu) is synthesized by sol–gel method with ethylene diamine tetraacetic acid and citric acid as co-complexing agents. The XRD shows NSFCu is stable after CO2 treatment and chemical compatible with SDC at high temperatures. CO2-TPD (CO2-temperature programmed desorption) demonstrates both CO2 adsorption and desorption phenomenon on NSFCu surface. However, the polarization resistances (Rp) of NSFCu and SDC (10:4 in weight) composite electrodes showed no decay in 5% CO2. Single cell using N2–O2–CH4 mixed gas (CH4 to O2 ratio = 1.5) as fuel shows maximum power density of 635 mW cm−2 at 700 °C. These results suggest that NSFCu-SDC is a promising composite cathode material for application in single-chamber solid oxide fuel cell.

•The properties of LTO/GS are dependent on Li precursors and calcination atmospheres.•Oxygen in the molecular structure of lithium precursor consumes GS.•The interaction between Li precursors and GO restricts the phase growth of LTO/GS.•LTO/GS obtained from LiOH precursor in reducing atmosphere has the best performance.The influence of Li precursors and calcination atmospheres on the reaction mechanisms, physical properties and electrochemical performance of graphene sheets (GS)-modified nano-Li4Ti5O12 (LTO/GS) has been systematically investigated. Field emission scanning electron microscopy (FE-SEM) and mass spectrometry (MS) results demonstrate the lithium precursor containing carboxyl anion such as lithium acetate (LiAc) and Li2CO3 interact with oxygen groups of graphene oxide (GO) by strong hydrogen bonds to restrict the morphology and the phase formation of products. We also notice from the thermogravimetry (TG) and MS results that the consumption of GS is proportional to oxygen content of lithium precursor. Cyclic voltammetry (CV) and X-ray photoelectric spectroscopy (XPS) results indicate that the product calcined in reducing atmosphere possess smaller electrochemical polarization due to more reduced Ti3+ on the surface of the product. The LTO/GS sample with LiOH as Li precursor calcined in diluted hydrogen atmosphere show the best electrochemical performance with a capacity of 134.4 mAh g−1 at 10C discharge rate and very stable cycling life with a 98.6% capacity retention after 800 cycles at 40C rate. This study not only provides an optimization of Li precursor and calcination condition for LTO/GS anode material, but also guides any future one-step syntheses of lithium composite materials with GO participation.

•Solvothermal routes to construct 3D graphene-based structures were compared.•In situ route facilitates forming desirable interfacial effects between GS and Fe2O3.•The effects result from the forceful Fe–O–C bonds between nano-Fe2O3 and few-layer GS.•Characterizations verified the advantages of the in situ solvothermal strategy.Solvothermal techniques were developed on the hydrothermal methods, and such methods especially in in situ fields have advantages in constructing functional three dimensional (3D) graphene-based composites in many aspects. To verify this concept, we presented in this article by comparing their application on the preparation of 3D Fe2O3/graphene sheets (Fe2O3/GS) composites, which are used as anode materials for lithium-ion batteries (LIB) and served as a probe here for exploring the merits from in situ solvothermal techniques. The ex situ solvothermal and in situ hydrothermal methods were adopted for comparison purpose. Physically, it was found that the in situ solvothermal process facilitates forming attractive interfacial interaction between GS and Fe2O3 resulting from the well wrapping and homogeneous distribution of nano-Fe2O3 particles into the 3D GS matrix and the forceful Fe–O–C bonds between nano-Fe2O3 and few-layer GS. We also confirmed electrochemically that the as-prepared 3D Fe2O3/graphene prepared by a in situ solvothermal technique showed better performance than those obtained via ex situ solvothermal and in situ hydrothermal methods. The in situ solvothermal strategy, if well engineered, can be extended to the synthesis of other high-performance 3D graphene-based materials for many other applications.Three-dimensional self-assembled Fe2O3/graphene sheets composites as anode materials for lithium ion batteries are prepared by integrating in situ solvothermal (IS), ex situ solvothermal (ES) and in situ hydrothermal (IH) methods, which is used as an example to systematically clarify the interfacial interaction between Fe2O3 and graphene and further evaluate the benefits of in situ solvothermal synthesis strategy.

A novel graphene sheet-wrapped cobalt hydroxide chloride composite (Co2(OH)3Cl@GS) is synthesized by a facile one-pot and in situ growth, hydrothermal method, which presents dramatically improved cycling stability and rate capability for long-life lithium ion battery. These exceptional performances are attributed to the introduction of a chlorine group and the extraordinary synergistic effect between Co2(OH)3Cl and GS.

A novel, flexible and binder-free reduced graphene oxide/Na2/3[Ni1/3Mn2/3]O2 composite electrode (GNNM) has been fabricated by a simple technique. Reduced graphene oxide (RGO) establishes stable electrically conductive structures in the GNNM electrode. The prepared GNNM electrode delivers 86 mA h g−1 at 0.1 C rate, and the capacity retention reaches 68.4% at 10 C rate. The discharge capacity of the GNNM electrode at 1 C rate can reach 80 mA h g−1 after 200 cycles.

A structure optimized Prussian blue analogue Na1.76Ni0.12Mn0.88[Fe(CN)6]0.98 (PBMN) is synthesized and investigated. Coexistence of inactive Ni2+ (Fe–CN–Ni group) with active Mn2+/3+ (Fe–CN–Mn group) balances the structural disturbances caused by the redox reactions. This cathode material exhibits particularly excellent cycle life with high capacity (118.2 mA h g−1).

A feasible and scalable two-step method is developed to synthesize LiFeSO4Fy(OH)1−y which could deliver 92 and 80 mA h g−1 when cycled at 1 C and 15 C, respectively. Moreover, with 80% of capacity retention after 2800 cycles at 1 C, this material should be of great interest as a contender to LiFePO4 for use in high power Li-ion batteries.

•Dual-layer NiO–YSZ/p-YSZ hollow fibers were co-spun through phase-inversion process.•MT-SOFCs with controllable AFLs were fabricated based on the dual-layer microtubes.•A prepared MT-SOFC fueled with CH4 was stably operated for 85 h.NiO–YSZ/porous YSZ (NiO–YSZ/p-YSZ) dual-layer hollow fibers have been fabricated by a co-spinning-sintering method, on which a dense YSZ films has been formed by a dip-coating and sintering process. A LSM–YSZ ink has been dip-coated on the dense YSZ films as cathode, while the Cu–CeO2 carbon-resistant catalyst has been impregnated in the p-YSZ layer to form double-anode supported micro tubular fuel cells (MT-SOFCs). The thickness of the Ni-YSZ layer, so called anode functional layer (AFL), is controlled from 74 μm to 13 μm by varying the spinning rates of the NiO–YSZ dopes. The maximum power density of an MT-SOFC, which is fabricated based on a thin co-spun AFL, reaches 566 mW cm−2 operated at 850 °C fed with dry methane, and is stably operated for 85 h without power declination.

•A novel NiO-YSZ/porous YSZ dual-layer hollow fiber for MT-SOFC preparation.•Carbon-resistant Ni-YSZ/Cu–CeO2-YSZ dual-layer anode is applied to MT-SOFC.•CH4 cracks mainly on Cu–CeO2-YSZ layer without carbon formation.A NiO-YSZ/porous YSZ dual-layer hollow fiber with an asymmetric structure was fabricated by a co-spinning-sintering method. A dense YSZ electrolyte film was prepared on NiO-YSZ layer by dip-coating method and calcined at 1450 °C; subsequently a porous cathode was dip-coated on the dense YSZ electrolyte film using LSM-YSZ (in the weight ratio 4:1) ink to fabricate a micro tubular solid oxide fuel cell (MT-SOFC). Cu–CeO2 catalyst was impregnated into the porous YSZ layer to form the second anode composition. The power output of the MT-SOFC with Ni-YSZ/Cu–CeO2-YSZ graded anode was up to 242 mW cm−2 operated at 850 °C using CH4 as fuel and air as oxidant. Little carbon deposition was observed on the double anode using methane as the fuel after 60 h' stable operation.

This study addresses the robust optimal source–sink matching in carbon capture and storage (CCS) supply chains under uncertainty. A continuous-time uncertain mixed-integer linear programming (MILP) model with physical and temporal constraints is developed, where uncertainties are described as interval and uniform distributed stochastic parameters. A worst-case MILP formulation and a robust stochastic two-stage MILP formation are proposed to handle interval and stochastic uncertainties, respectively. Then, two illustrative case studies are solved to demonstrate the effectiveness of the proposed models for planning CCS deployment under uncertainty.

•Composite cathode can significantly improve the performance of cathode in SOFC.•Addition of the second phase has an optimum value for composite cathode.•Overloading second phase has a negative influence on composite cathode.•The cell shows the best performance at 40 wt% SDC as second phase.Cobalt-free composites Nd0.5Sr0.5Fe0.8Cu0.2O3−δ (NSFCu)–xSm0.2Ce0.8O1.9 (SDC) (x = 0–60 wt%) are investigated as IT-SOFC cathodes. The characteristic properties of cobalt-free composite cathodes comparing to cobalt-based composites are revealed. The DC conductivity and thermal expansion coefficient of the composite cathodes decrease with the content of SDC x, while the polarization resistance Rp shows the least value with addition of 40 wt% of SDC. The power density of the single cell with NSFCu-40% SDC composite cathode improved significantly compared with that of undoped NSFCu cathode, with peak values of 488, 623, 849 and 1052 mW cm−2 at 600, 650, 700, and 750 °C, respectively. Moreover, the performance of the composite cathode is stable within testing period of 370 h at 700 °C, indicating that the NSFCu-40% SDC is an excellent cobalt-free composite cathode applied in IT-SOFC.

Novel cobalt-free perovskite oxides NdxSr1–xFe0.8Cu0.2O3−δ (NSFCx, 0.3 ≤ x ≤ 0.7) have been prepared and evaluated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFC). Their structure, thermal expansion, electric, and electrochemical properties are investigated. The oxides exhibit all cubic structure and show excellent thermal and electrochemical performance stability. The Nd content (x) significantly affects the properties of NSCFx. NSFC0.5 has been found to be the optimum composition with a peak electrical conductivity of 124 S cm–1 at 700 °C, an average thermal expansion coefficient of 14.7 × 10–6 K–1 over 25–800 °C, a cathodic polarization resistance (Rp) of 0.071 Ω cm2 at 700 °C, and a peak power density of 900 mW cm–2 at 800 °C for samarium-doped ceria (SDC)-based single cells with NSFCx cathodes and Ni–SDC anodes. Moreover, no degradation has been observed for the Rp at 700 °C within 350 h. The concentration of surface oxygen vacancies and composition dependent crystallographic parameters have been found to be the dominating factors on performance of NdxSr1–xFe0.8Cu0.2O3−δ as IT-SOFC cathodes.

Y2O3-stabilized-ZrO2(YSZ)/La0.8Sr0.2MnO3-α(LSM)–YSZ dual-layer hollow fibers have been fabricated for micro-tubular solid oxide fuel cells (MT-SOFCs) using a co-spinning/co-sintering technique. The hollow fibers consist of a dense YSZ top layer supported on the porous LSM–YSZ substrate with an asymmetric structure. The electrolyte and the cathode layers are perfectly adhered to each other without observable elemental inter-diffusion. Both the mechanical strength of the hollow fibers and the compactness of the electrolyte layer are improved by increasing the sintering temperature, whereas the effective porosity of the cathode layer also decreases. The suitable sintering temperature of the YSZ/LSM–YSZ dual-layer hollow fibers to construct the electrolyte/cathode half-cells should be controlled between 1350 °C and 1400 °C. An Ni-YSZ layer of about 5 μm in thickness is dip-coated on the outer surface of the hollow fibers to serve as the anode of fuel cells. The resultant micro-tubular SOFCs yield a maximum power density of 290 mW cm−2 at 850 °C using 1.49 × 10−5 mol s−1 hydrogen as fuel and 2.23 × 10−5 mol s−1 air as oxidant, respectively. The output performance of the micro-tubular fuel cells is mainly limited by the high polarization resistance of the cathode.Highlights► Asymmetric YSZ/LSM–YSZ dual-layer hollow fibers were prepared in a single step. ► A suitable sintering temperature range of 1350–1400 °C for the fibers was given. ► Cathode-supported MT-SOFCs were obtained by dip-coating anode on outer surface. ► A maximum power density of 290 mW cm-2 was obtained at 850 °C for the MT-SOFCs. ► Microstructure of the cathode layer has to be improved for higher output density.

In this study, a series of Fe-based non-noble metal and non-macrocycle catalysts, FeTETA/C, for oxygen reduction reaction (ORR) have been synthesized by pyrolyzing carbon-supported iron triethylenetetramine chelate at various temperatures in an inert atmosphere. Electrochemical characterization revealed that heat treatment temperature plays an essential role on improving the catalytic property of the obtained catalysts for ORR, and the optimal could be achieved at 800 °C with an ORR peak potential of 0.751 V and an electron-transfer number of 3.85. Furthermore, the obtained optimal catalyst has excellent methanol-tolerance and acceptable acid-resistance. The effects of heat treatment temperature on microstructure of the catalysts as well as the elemental state on the optimal catalyst surface have been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).

•P2-Na2/3[Ni1/3Mn2/3]O2 was synthesized via spray drying method and a two step solid state process.•Cycling performance of P2-Na2/3[Ni1/3Mn2/3]O2 cathode was studied in different voltage ranges.•The prepared material showed excellent reversibility between 2.0 V and 4.0 V with good capacity retention.•Cycled in 2.0–4.5 V, the crystal structure of P2-Na2/3[Ni1/3Mn2/3]O2 was irreversibly damaged.•The discharge capacities increased to 134.7 mA g−1 (0.1 C) and 107.8 mA g−1 (1 C), cycled in 1.6–3.8 V.P2-type Na2/3[Ni1/3Mn2/3]O2 cathode material has been synthesized via spray drying method and a two step solid state process. Electrochemical behavior of the prepared material as cathode material for sodium ion battery was investigated in different charge-discharge voltage ranges. The results indicated that the cycling performance of the P2-Na2/3[Ni1/3Mn2/3]O2 cathode greatly depended on the voltage window. The material showed excellent reversibility between 2.0 V and 4.0 V with reversible capacity of 86 mAh g−1 (0.1 C) and 77 mAh g−1 (1 C). XRD analyses indicated that crystal structure of the P2-type Na2/3[Ni1/3Mn2/3]O2 could be well maintained after long term cycling in 2.0–4.0 V. When the upper limiting voltage was increased to 4.5 V, the crystal structure of P2-Na2/3[Ni1/3Mn2/3]O2 was irreversibly damaged due to over extraction of Na+ in 4.0–4.5 V. On the other hand, when the cycling voltage range was between 1.6 V and 3.8 V, the discharge capacities increased to 135 mAh g−1 (0.1 C) and 108 mAh g−1 (1 C), respectively. However, the cycling stability in 1.6–3.8 V was not as excellent as that in 2.0–4.0 V. This maybe due to the lattice stress caused by the over insertion of Na+ in the structure at lower voltage.

•Pr0.5Sr0.5Fe0.8Cu0.2O3−δ (PSFC) is synthesized and evaluated as SOFC cathode.•The Rp of PSFC cathode on SDC electrolyte is as low as 0.050 Ω cm2 at 700 °C.•The peak power density of a zirconia based single cell is 1077 mW cm−2 at 800 °C.A new cobalt-free perovskite oxide Pr0.5Sr0.5Fe0.8Cu0.2O3−δ (PSFC) has been synthesized and evaluated as cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The chemical compatibility of PSFC with Sm0.2Ce0.8O1.9 (SDC) electrolyte has be proven by XRD, and its electrical conductivity reaches the maximum value of 264.1 S cm−1 at 475 °C. Symmetrical cells with the configuration of PSFC/SDC/PSFC are used for the impedance study and the polarization resistance (Rp) of PSFC cathode is as low as 0.050 Ω cm2 at 700 °C. Single cells, consisting of Ni–YSZ/YSZ/SDC/PSFC structure, are assembled and tested from 550 °C to 800 °C with wet hydrogen (∼3% H2O) as fuel and static air as oxidant. A maximum power density of 1077 mW cm−2 is obtained at 800 °C. All the results suggest that the cobalt-free perovskite oxide PSFC is a very promising cathode material for application in IT-SOFC.

•YSZ/Ni-YSZ dual-layer hollow fibers (DL-HFs) were co-spun-sintered by one step.•The microstructure of the DL-HFs was tailored by adding ethanol in NiO-YSZ dopes.•A maximum power density of 485 mW cm−2 was obtained at 850 °C for the MT-SOFCs.YSZ/NiO-YSZ dual-layer hollow fibers with a thin YSZ top layer integrated on a porous NiO-YSZ (60:40 in weight) support, have been developed by one step method via a co-spinning-sintering process. Hydrogen reduction was performed to form YSZ/Ni-YSZ micro tube as the half solid oxide fuel cells (SOFCs). The microstructure of the dual-layer hollow fibers was tailored by adding ethanol as non-solvent in the initial mixture dopes for NiO-YSZ anode spinning. LSM cathode containing 20 wt%-YSZ was deposited on the electrolyte surface by dip-coating method to fabricate micro-tubular SOFCs. Experimental results indicate that the dual-layer hollow fibers from the anode dopes containing 15–20 wt% of ethanol possess the desired microstructure with optimized properties, such as the bending strength of 180 MPa, the porosity of 38–35% and the conductivity of 3000 S cm−1 at room temperature. The micro-tubular SOFCs fabricated from such hollow fibers show a maximum power density up to 485 mW cm−2 at 850 °C with 20 mL min−1 of H2 as fuel and 30 mL min−1 air as oxidant, respectively.

A promising non-precious metal FeCoTETA/C catalyst has been easily synthesized, by chelating Fe and Co with triethylenetetramine (TETA) in ethanol followed by pyrolyzing in an Ar atmosphere, as electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). The catalyst has been characterized with various physicochemical techniques as well as electrochemical analysis and single cell performance measurement. The results showed that nano-intermetallic FeCo particles and several types of N and O species are present on carbon matrix. The catalyst delivers better electrocatalytic activity toward ORR compared with CoTETA/C catalyst, the %H2O2 is about 10% with an electron-transfer number of around 3.8. The PEMFC with this catalyst in cathode reaches a maximum power density of 256 mW cm−2 and has a current density of 514 mA cm−2 at 500 mV.

A novel Co(phen)2/C catalyst was prepared by coating cobalt(II) phenanthroline (phen) chelate on BP2000 carbon black and then heat treating in an inert atmosphere. The obtained Co(phen)2/C product with 1.0 wt% cobalt loading exhibits similar morphology and porosity characteristics to those of the bare BP2000. X-ray diffraction measurements demonstrate a face-centered cubic (fcc) α-Co phase embedded in the carbon support after pyrolysis. Charge/discharge tests of the lithium-oxygen cells using the prepared Co(phen)2/C catalyst show high discharge capacities of 4870 mAh g−1 (0.05 mA cm−2), 3353 mAh g−1 (0.1 mA cm−2) and 3220 mAh g−1 (0.15 mA cm−2), respectively. The Co(phen)2/C cathode exhibits reasonable reversibility with capacity retention of 1401 mAh g−1 (0.1 mA cm−2) after 10 cycles. The superior electrochemical performance of the prepared Co(phen)2/C catalyst and low cost of the phenanthroline chelating agent indicate that Co(phen)2/C is a promising cheap catalyst for lithium-air batteries.

A LiFePO4/C-polypyrrole (LiFePO4/C-PPy) composite as a high-performance cathode material is successfully prepared through a simple chemical vapor deposition (CVD) method. According to the transmission electron microscope (TEM) analysis, the surface of the LiFePO4/C is surrounded with PPy in the LiFePO4/C-PPy composite. The as-prepared LiFePO4/C-PPy material shows outstanding rate capability at 20°C and good cycle performance at 55°C in comparison with those of the bare LiFePO4/C material against Li anode. After 700 cycles, the discharge capacity of LiFePO4/C-PPy could still remain 110 mA h g−1 with the retention of 82% at 5 C rate at 55°C. This could be ascribed to the fact that PPy coating on LiFePO4/C could significantly improve the ionic conductivity of the LiFePO4/C-PPy composite and could greatly reduce the electrode resistance. Furthermore, the PPy coating on LiFePO4/C could effectively decrease the dissolution of Fe in the LiPF6 electrolyte and subsequently suppress the reduction of Fe ions on anode.

The potential stability windows of chemical converted graphene in different aqueous electrolyte solutions were investigated for the first time. Based on this result, a supercapacitor with a high voltage and long cycle-life was prepared with the hydrated graphene films in the neutral aqueous solution at the maximum voltage of 1.6 and even 1.8 V. The electrochemical performance of the obtained sample was systematically investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. According to the cyclic voltammetry, hydrated graphene film can still retain rectangular shape at the high scan rate of 0.5 V/s in the neutral aqueous electrolyte. At a galvanostatic charge/discharge rate of 1 or 200 A/g, the specific capacitance of 202.3 or 138.1 F/g was delivered, respectively. Furthermore, the EIS results also confirm its fast neutral ion diffusion and high operating frequency of 9.34 Hz.Highlights► Potential window of chemically converted graphene is 1.8V in neutral aq. solution. ► Hydrated graphene film-based supercapacitor can operate at 1.8 V in neutral solution. ► At 1 and 200 A/g, its specific capacitances reach 197.6 and 138.1 F/g. ► Its operating frequency is as high as 9.34 Hz together with the scan rate over 1 V/s.

ZnS/C composites were synthesized by a combined precipitation with carbon coating method. Morphology and structure of the as-prepared ZnS/C composite materials with carbon content of 4.6 wt%, 9.3 wt% and 11.4 wt% were characterized using TEM and XRD technique. TEM observation demonstrated that the ZnS/C (9.3 wt% C) composite showed excellent microstructure with 20–30 nm ZnS nanoparticles uniformly dispersed in conductive carbon network. Electrochemical tests showed that the ZnS/C (9.3 wt% C) composite presented superior performance with initial charge and discharge capacity of 1021.1 and 481.6 mAh/g at a high specific current of 400 mA/g, after 300 cycles, the discharge capacity of ZnS/C electrode still maintained at 304.4 mAh/g, with 63.2% of its initial capacity. The rate capability and low temperature performance of the ZnS/C (9.3 wt% C) composite were compared with commercial MCMB anode. The results showed that the ZnS/C (9.3 wt%) composite exhibited much better cycle capability and low temperature performance than MCMB anode. ZnS/C composite seems to be a promising anode active material for lithium ion batteries. Intercalation mechanism of the ZnS/C composites for lithium ion insertion–extraction is proposed based on the ex situ X-ray diffraction analysis incorporating with its electrochemical characteristics.

A novel bath lily-like graphene sheet-wrapped nano-Si composite synthesized via a simple spray drying process exhibits a high reversible capacity of 1525 mAh g−1 and superior cycling stability, which could be attributed to a synergistic effect between highly conductive graphene sheets and active nanoparticles in the open nano/micro-structure.

A systematic study and evaluation were performed on the effect of scandium doping at the B site of Pr0.6Sr0.4Co0.2Fe0.8O3−δ (PSCF) on key material properties as cathode for intermediate temperature solid oxide fuel cells (IT-SOFC). The doped products Pr0.6Sr0.4(Co0.2Fe0.8)(1−x)ScxO3−δ (PSCFSx, x=0.0–0.2) retained perovskite structure confirmed by X-ray diffraction, and their particles were smaller than the non-doped materials as evidenced by TEM. The electrical conductivity (EC) of PSCFSx decreased with increasing Sc3+ content, but EC values were still larger than 100 S cm−1 in temperature range of 300–800 °C as x ≤ 0.1. The thermal expansion coefficients (TEC) of PSCFSx were observed to generally decrease with increasing x especially at lower temperature range of 50–600 °C. In addition, the AC impedance revealed better electrochemical performance of PSCFSx cathode as x ≤ 0.1 than that of the undoped sample PSCF. Therefore, PSCFSx (x ≤ 0.1) shows some potential as cathode electrode for IT-SOFC. The function of Sc3+ dopant was tentatively elucidated and discussed.Research highlights► Scandium doped Pr0.6Sr0.4Co0.2Fe0.8O3–δ was evaluated as cathode of IT'SOFC. ► The doped products Pr0.6Sr0.4(Co0.2Fe0.8)(1–x)ScxO3–δ (PSCFSx) showed smaller particles. ► The conductivity and thermal expansion coefficients of PSCFSx (x = 0.0∼0.2) decreased as raising x. ► PSCFSx (x ≤ 0.1) exhibited better cathode performance than PSCF and PSCFSx (x > 0.1) did. ► The function of Sc3+ dopant was tentatively elucidated and discussed.

Ag promoted ZnO/Al2O3 catalysts were prepared by using the incipient wetness impregnation method. The catalytic properties of steam reforming reaction for hydrogen production on the prepared catalysts were evaluated with H2O:C2H5OH molar ratios of 3:1 at 450 °C and atmospheric pressure. Ag promoted ZnO/Al2O3 catalysts show higher SRE catalytic activity than ZnO/Al2O3 catalysts. H2 and CH3CHO are the major products on Ag promoted catalysts, and C2H4 is also produced probably due to acid sites on Al2O3. SRE mechanism on Ag promoted ZnO/Al2O3 catalysts, which contains C–C scission, is different from that on ZnO/Al2O3 catalysts. A method based on thermogravimetry (TG), differential scanning calorimetry (DSC) and mass spectrometry (MS) was used to analysis the coking behavior on catalyst surface. The surfaces of Ag promoted ZnO/Al2O3 catalysts show two different types of coking, and suffer higher coke deposition during the steam reforming reaction.

Effect of preparation method for Pr0.6Sr0.4Co0.2Fe0.8O3 − δ (PSCF) on its electrochemical performance was investigated. Powder samples were synthesized by hexamethylenetetramine (HMTA) and EDTA–citric acid (EC) techniques, respectively. The particles synthesized by HMTA were smaller than those prepared by EC method as proved by TEM. X-ray photoelectron spectroscopy illuminated that more oxygen sites including oxygen vacancy on the surface of HMTA-derived PSCF exist than that of EC-derived PSCF. The area specific resistance (ASR) value of HMTA-derived PSCF cathode was as low as 0.454 Ω cm2 at 600 °C, whereas the ASR value of EC-derived PSCF was 0.641 Ω cm2. The results in the present study demonstrated the advantages of the HMTA method in the synthesis of highly catalytic active PSCF oxide powder for SOFCs.Research Highlights► PSCF cathode powders were synthesized by HMTA and EC methods. ► The HMTA–derived PSCF cathode displays smaller particle size and lower ASR. ► HMTA-derived PSCF shows more surface oxygen vacancy tested by XPS.

A novel catalyst, Co-PPy-TsOH/C, for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) was prepared by pyrolyzing cobalt salt and p-toluenesulfonic acid (TsOH)-doped polypyrrole-modified carbon support in an inert atmosphere. The characteristics and electrocatalytic activities of Co-PPy-TsOH/C were analyzed with various techniques, including Raman spectroscopy, elemental analysis, rotating ring disk electrode analysis, and a single H2−O2 PEMFC, and compared with those of undoped catalyst Co-PPy/C. The results showed that doping TsOH introduces larger N and S contents in Co-PPy-TsOH/C, leading to much better electrocatalytic performance for ORR than Co-PPy/C, and that Co-PPy-TsOH/C is more likely to follow a four-electron-transfer reaction to reduce oxygen directly to H2O. The performance of PEMFCs with Co-PPy-TsOH/C as cathode catalyst is better than that with Co-PPy/C, and the resulting maximum output power density of 203 mW cm−2 is a substantial improvement over the best values reported in the literature with Co-PPy/C-based cathode catalyst. This implies that doping TsOH is a valuable method to improve the catalytic activity of Co-PPy/C and that Co-PPy-TsOH/C is a promising cathode catalyst for PEMFCs. The function and mechanism of doping have also been analyzed and the configurations of PPy-TsOH/C and Co-PPy-TsOH/C proposed.

A Co(OH)2−graphene nanosheets (Co(OH)2−GNS) composite as a high performance anode material was firstly prepared through a simultaneous hydrothermal method. The structure, morphology and electrochemical performance of the obtained samples were systematically investigated by X-ray diffraction (XRD), transmission electron microscope (TEM) and electrochemical measurements. According to the TEM analysis, the surface of the Co(OH)2 is surrounded with GNS in the Co(OH)2−GNS composite. The specific discharge (lithiation) and charge (delithiation) capacities of Co(OH)2−GNS attain to 1599 and 1120 mAh/g at a current density of 200 mA/g in the first cycle, respectively. After 30 cycles, the reversible capacity of Co(OH)2−GNS is still 910 mAh/g with the retention of 82%. The particular structure of Co(OH)2 particles surrounded by the GNS could limit the volume change during cycling and provide an excellent electronic conduction pathway, which could be the main reason for the remarkable improvement of electrochemical performance.

A novel platinum-free electrocatalyst CoTETA/C for oxygen reduction reaction (ORR) was prepared from pyrolysis of carbon-supported cobalt triethylenetetramine chelate under an inert atmosphere. X-ray diffraction (XRD) measurement showed that nanometallic face-centered cubic (fcc) crystalline α-Co phase embedded in graphitic carbon was present on the pore surface of this catalyst. Cyclic voltammogram experiment showed that the ORR peak potential appears at 710 mV (vs. NHE) in oxygen-saturated acidic media (0.5 M H2SO4). The Koutecky–Levich analysis indicated that the ORR follows the first-order kinetic reaction and the ORR proceeds via both the two-electron reduction and the four-electron reduction, while the latter is the main process. The actual performance of a single cell with the obtained CoTETA/C electrocatalyst was examined under a hydrogen-oxygen fuel cell system, and the maximal output power density reached 135 mW cm−2 at 25 °C.

In this communication, we report a novel CoTETA/C catalyst for the oxygen reduction reaction (ORR) which was prepared from a carbon-supported cobalt triethylenetetramine chelate, followed by heat treatment in an inert atmosphere. Electrochemical performances were measured using rotating disk electrode (RDE) technique and a PEM fuel cell test station. For a H2–O2 fuel cell system, the maximum output power density reached 162 mW cm−2 at 25 °C with non-humidified reaction gases. We found a nanometallic face-centered cubic (fcc) α-Co phase embedded in the graphitic carbon after pyrolysis, based on X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) measurements. These results indicated that CoTETA/C is a promising catalyst for the ORR.

Constructed here is a mathematic model of PEM Fuel Cell Vehicle Power System which is composed of fuel supply model, fuel cell stack model and water-heat management model. The model was developed by Matlab/Simulink to evaluate how the major operating variables affect the output performances. It shows that the constructed model can represent characteristics of the power system closely by comparing modeling results with experimental data, and it can be used in the study and design of fuel cell vehicle power system.

NiO/YSZ hollow fibers were fabricated via a combined phase inversion and sintering technique, where polyethersulfone (PESf) was employed as the polymeric binder, N-methyl-2-pyrrolidone (NMP) as the solvent and polyvinylpyrrolidone (PVP) as the additive, respectively. After reduction with hydrogen at 750 °C for 5 h, the porous Ni/YSZ hollow fibers with an asymmetric structure comprising of a microporous layer integrated with a finger-like porous layer were obtained, which can be served as the anode support of micro-tubular solid oxide fuel cells (SOFCs). As the sintering temperature was increased from 1200 to 1400 °C, the mechanical strength and the electrical conductivity of the Ni/YSZ hollow fibers increased from 35 to 178 MPa and from 30 to 772 S cm−1, respectively but the porosity decreased from 64.2% to 37.0%. The optimum sintering temperature was found to be between 1350 and 1400 °C for Ni/YSZ hollow fibers applied as the anode support for micro-tubular SOFCs.

Co-substituted α-Ni(OH)2 was synthesized by a novel microwave homogeneous precipitation method in the presence of urea. LiNi0.8Co0.2O2 cathode material was synthesized by calcining Co-substituted α-Ni(OH)2 precursor and LiOH·H2O at 900°C for 10 h in flowing oxygen. XRD, FTIR, FESEM and electrochemical tests were used to study the physical and the electrochemical performances of the materials. The results show that the prepared LiNi0.8Co0.2O2 compound has a good layered hexagonal structure. Moreover, the LiNi0.8Co0.2O2 cathode material demonstrates stable cyclability with a high initial specific discharge capacity of 183.9 mAh/g. The good electrochemical performance could be attributed to the uniform distribution of Ni2+ and Co2+ ions in the crystal structure and a minimal cation mixing in LiNi0.8Co0.2O2 host structure.

Low platium loading Pt/C catalyst was prepared by direct Pt-embedded carbon xerogel method. The Pt content of the as-prepared Pt/C is about 4.32 wt% and has a typical polycrystalline phase. Textural and structural characteristics of the catalysts were characterized by XRD, EDS and BET. Pt-embedded in carbon xerogel increases the specific surface area and pore volume of the X-Pt/C during carbon gelation and the carbonization process. Electrochemical characteristics of the catalysts for ethanol electrooxidation were measured. The results indicated that the as-prepared 4.32 wt% Pt/C has higher mass current density in ethanol electrooxidation as compared to the 20 wt% Pt/C. This may be due to the high roughness of the Pt surface that is formed during the carbon gelation and carbonization process.

Submicron-sized LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized using a simple self-propagating solid-state metathesis method with the help of ball milling and the following calcination. A mixture of Li(ac)·2H2O, Ni(ac)2·4H2O, Co(ac)2·4H2O, Mn(ac)2·4H2O (ac = acetate) and excess H2C2O4·2H2O was used as starting material without any solvent. XRD analyses indicate that the LiNi1/3Co1/3Mn1/3O2 materials were formed with typical hexagonal structure. The FESEM images show that the primary particle size of the LiNi1/3Co1/3Mn1/3O2 materials gradually increases from about 100 nm at 700 °C to 200–500 nm at 950 °C with increasing calcination temperature. Among the synthesized materials, the LiNi1/3Co1/3Mn1/3O2 material calcined at 900 °C exhibits excellent electrochemical performance. The steady discharge capacities of the material cycled at 1 C (160 mA g−1) rate are at about 140 mAh g−1 after 100 cycles in the voltage range 3–4.5 V (versus Li+/Li) and the capacity retention is about 87% at the 350th cycle.

The effects of fluorine substitution on the electrochemical properties of LiFePO4/C cathode materials were studied. Samples with stoichiometric proportion of LiFe(PO4)1−xF3x/C (x = 0.025, 0.05, 0.1) were prepared by adding LiF in the starting materials of LiFePO4/C. XRD and XPS analyses indicate that LiF was completely introduced into bulk LiFePO4 structure in LiFe(PO4)1−xF3x/C (x = 0.025, 0.05) samples, while there was still some excess of LiF in LiFe(PO4)0.9F0.3/C sample. The results of electrochemical measurement show that F-substitution can improve the rate capability of these cathode materials. The LiFe(PO4)0.9F0.3/C sample showed the best high rate performance. Its discharge capacity at 10 C rate was 110 mAh g−1 with a discharge voltage plateau of 3.31–3.0 V versus Li/Li+. The LiFe(PO4)0.9F0.3/C sample also showed obviously better cycling life at high temperature than the other samples.

CoTMPP-TiO2NT/BP composites have been synthesized by preparing CoTMPP and depositing CoTMPP on carbon-supported titania nanotube (TiO2NT/BP) using microwave irradiation method at the same time, followed by heat-treatment from 300 to 900 °C in N2 atmosphere. The catalytic activity for oxygen reduction was evaluated by rotating disc electrode technique in half cells with 0.5 M H2SO4. The number of electrons exchanged during ORR and the percentage of peroxide (%H2O2) produced by the reaction were evaluated for catalysts by rotating ring disk electrode (RRDE) measurements. The influences of TiO2NT doping, the heat-treating temperature and the different ratios of BP:TiO2NT on the activity of electrocatalysts for oxygen reduction were investigated. The stability of the CoTMPP-TiO2NT/BP electrocatalysts was studied with potentialstatic-polarization measurements in 0.5 M H2SO4 + 0.5 M CH3OH. CoTMPP-TiO2NT/BP composites show higher catalytic activity and better stability than CoTMPP/BP. The mechanism for the enhanced catalytic activity of CoTMPP-TiO2NT/BP is discussed.

Carbon xerogel (CX), a kind of novel carbon material with low-density and continuous nano-porous structure that can be controlled and tailored on nanometer scale, has been prepared through the sol–gel polycondensation of resorcinol (R) with formaldehyde (F) followed by drying at ambient pressure and carbonization in inert atmosphere, and CX–SiO composite has been synthesized by high energy mechanical ball-milling of the obtained CX and commercial SiO at room temperature and atmosphere. The characteristics of CX and CX–SiO as anode material for lithium-ion battery have been systematically investigated on basis of field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), electrochemical and charge–discharge tests. The results showed that, CX–SiO is composed of active carbon, graphite, SiO and dispersed Si crystal while CX consists of active carbon and graphite, CX–SiO has smaller and much more uniform particles than CX. SiO can greatly improve discharge capacity of CX with an acceptable sacrifice of cycling stability, and the charge–discharge capacity of CX–SiO comes mainly from lithium insertion–extraction in Si–SiO in the sample.

Microwave synthesis method was applied to prepare CoTMPP/BP oxygen reduction electrocatalysts. The influence of the pre-treatment of BP2000 carbon supports by 6 M HNO3 and 30 wt% H2O2 on the activity of electrocatalysts for oxygen reduction was investigated by means of the measurements of their electrochemical characteristics and performances. Levich–Koutecky plot shows that the number of transferred electrons during oxygen reduction on CoTMPP/BP is found to be between 2 and 4. The observed evidence indicated that the production of hydrogen peroxide has occurred during oxygen reduction in two electrons, and further oxidation of hydrogen peroxide involving two other electrons in the higher potential may also occur. The fuel cell performance of single cells with the different CoTMPP/BP electrocatalysts was examined under actual PEM fuel cell conditions. For hydrogen–oxygen fuel cell system, the maximal output power density reached 150 mW/cm2 at 50 °C. Life test was carried out at a constant of the output current density of 200 mA/cm2 for CoTMPP/BP electrocatalyst, the single cell output voltage maintains at about 0.5 V for more than 900 min, there was no obvious performance degradation under fuel cell conditions.

The principle of galvanostatic intermittent titration technique (GITT) is introduced briefly. Hydrogen diffusion behavior in AB5-type hydrogen storage alloys MlNi3.75Co0.65Mn0.4Al0.2 have been electrochemically studied with GITT. The results showed that the hydrogen diffusion coefficient D in the alloys increases with the increase of depth of discharge (DOD) at ambient temperature. For the alloys with 50% DOD, the value of D increases with the increase of temperature, an approximately linear relationship exists between ln D and the reciprocal of the absolute temperature (1/T), and the activation energy for hydrogen diffusion in it has been calculated with Arrhenius equation to be about 21 kJ mol−1.

The electro-generative hydrogenation of allyl alcohol (AA) to 1-propanol was studied applying the PEM fuel cell reactor. The results indicated that AA can be converted to 1-propanol at the cathode, and electric power was generated simultaneously. No side reactions were observed during the operation. Open circuit cell potentials were around 0.25 V and current density varied from 4 to with the change of external load. The maximum power density was at a current density of during the hydrogenation of AA in water with the generation of electric power. According to the cyclic voltammetry (CV) measurement for the electro-reduction of AA, the hydrogenation of AA occurred near the positive potential of 250 mV before hydrogen evolution. CV measurement was in accord with the results observed in the hydrogenation of AA in the PEM fuel cell reactor.

Carbonaceous mesophase spherule (CMS) is a commercial anode material for rechargeable lithium batteries. A composite anode material of SnNi deposited carbonaceous mesophase spherule was prepared by co-precipitation method. The structural and electrochemical characterization of the SnNi/CMS composite anode material was studied. According to the measurement of its electrochemical characterization, the prepared SnNi/CMS composite anode material shows much better electrochemical performance than CMS. The first discharge capacity of 360 mA h g−1 was obtained for the SnNi/CMS composite anode material, and its discharge capacity maintained at 320–340 mA h g−1 in the following cycles. It indicates that the modification of CMS with SnNi alloy can further improve the intercalation performance of CMS. SnNi/CMS composite material shows a good candidate anode material for the commercial rechargeable lithium batteries.

Characteristics including microstructure, thermodynamics, electrochemical and kinetic properties of AB5-type hydrogen storage alloys La0.8(1−x)Ce0.8x(PrNd)0.2B5, where B5 is Ni3.55Co0.75Mn0.4Al0.3, were studied systematically. It indicated that these alloys have a typical single-phase structure of the CaCu5-type, the cell parameters of a and c changing slightly with the Ce content x. The equilibrium pressure of the alloys for hydrogen sorption increases with the increase of the Ce content, the hysteresis becomes smaller, and the thermodynamic stability of corresponding hydride becomes lower. The effect of the Ce content on the electrochemical activation of the alloys is negligible, while its effects on the discharge capacity, high-rate discharge ability, charge–discharge voltage and kinetic performance of the alloys are significant.

This review focuses on the application of process engineering in electrochemical energy conversion and storage devices innovation. For polymer electrolyte based devices, it highlights that a strategic simple switch from proton exchange membranes (PEMs) to hydroxide exchange membranes (HEMs) may lead to a new-generation of affordable electrochemical energy devices including fuel cells, electrolyzers, and solar hydrogen generators. For lithium-ion batteries, a series of advancements in design and chemistry are required for electric vehicle and energy storage applications. Manufacturing process development and optimization of the LiFePO4/C cathode materials and several emerging novel anode materials are also discussed using the authors' work as examples. Design and manufacturing process of lithium-ion battery electrodes are introduced in detail, and modeling and optimization of large-scale lithium-ion batteries are also presented. Electrochemical energy materials and device innovations can be further prompted by better understanding of the fundamental transport phenomena involved in unit operations.

A micro-cubic Prussian blue (PB) without coordinated water is first developed by electron exchange between graphene oxide and PB. The obtained reduced graphene oxide–PB composite exhibited complete redox reactions of the Fe sites and delivered ultrahigh electrochemical performances as well as excellent cycling stability as a cathode in sodium-ion batteries.

A structure optimized Prussian blue analogue Na1.76Ni0.12Mn0.88[Fe(CN)6]0.98 (PBMN) is synthesized and investigated. Coexistence of inactive Ni2+ (Fe–CN–Ni group) with active Mn2+/3+ (Fe–CN–Mn group) balances the structural disturbances caused by the redox reactions. This cathode material exhibits particularly excellent cycle life with high capacity (118.2 mA h g−1).

A feasible and scalable two-step method is developed to synthesize LiFeSO4Fy(OH)1−y which could deliver 92 and 80 mA h g−1 when cycled at 1 C and 15 C, respectively. Moreover, with 80% of capacity retention after 2800 cycles at 1 C, this material should be of great interest as a contender to LiFePO4 for use in high power Li-ion batteries.

A novel, flexible and binder-free reduced graphene oxide/Na2/3[Ni1/3Mn2/3]O2 composite electrode (GNNM) has been fabricated by a simple technique. Reduced graphene oxide (RGO) establishes stable electrically conductive structures in the GNNM electrode. The prepared GNNM electrode delivers 86 mA h g−1 at 0.1 C rate, and the capacity retention reaches 68.4% at 10 C rate. The discharge capacity of the GNNM electrode at 1 C rate can reach 80 mA h g−1 after 200 cycles.

A nitrogen-containing carbon (N–C) film was synthesized by pyrolysis of vapor phase polymerized polypyrrole (PPy). This carbon film exhibits excellent rate capability and cyclability as a lithium-ion battery anode. The reversible capacities are 908.4, 825.7, 664.0, 531.6, 415.5 and 325.9 mA h g−1 at 1C, 2C, 5C, 10C, 20C and 40C, respectively.

A novel graphene sheet-wrapped cobalt hydroxide chloride composite (Co2(OH)3Cl@GS) is synthesized by a facile one-pot and in situ growth, hydrothermal method, which presents dramatically improved cycling stability and rate capability for long-life lithium ion battery. These exceptional performances are attributed to the introduction of a chlorine group and the extraordinary synergistic effect between Co2(OH)3Cl and GS.

Micro-tubular SOFCs have the potential to become light-weight portable auxiliary power units for aircraft or spacecraft. In this work, a novel dual-layer ceramic hollow fiber for a cathode-supported micro-tubular solid oxide fuel cell (MT-SOFC) has been successfully developed via a co-spinning-sintering technique. The green cathode hollow fibers, in dual layer configuration, consisting of a La0.8Sr0.2MnO3−δ (LSM) main layer and a LSM–Y2O3 stabilized ZrO2 (YSZ) functional layer with increased three phase boundary length, are first prepared by co-spinning, which are then sintered at around 1350 °C to allow the creation of sufficient mechanical strength. Other cell components like the electrolyte (YSZ) and anode (NiO + YSZ) are then coated separately. The coated electrolyte film with a thickness of around 27 μm is obtained by co-sintering of YSZ/LSM–YSZ/LSM in a sandwich structure. The porous LSM substrate functions as an oxygen-supplying and current collecting layer. The prepared MT-SOFC, tested with hydrogen as the fuel and air as the oxidant, delivers a maximum power density of up to 475 mW cm−2 at 850 °C, which is much higher than that of a similar cell without a cathode functional layer.