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The development of batteries with high energy density and low costs involves chemistry beyond lithium‐ion batteries. Rechargeable sodium‐oxygen (Na−O2) batteries make two essential steps forward: i) replacing Li by Na to remove the bottleneck in resources supply and ii) using oxygen from air to raise the theoretical energy density. A lot of progress has been made in performance and understanding of Na−O2 battery since its first report in 2012. However, there remain significant challenges, such as the instability of discharge products, dendrite growth of Na metal, and the crossover of superoxide. A timely review is given here to summarize the challenges encountered in the components of the Na−O2 battery. Insights are offered on sodium anode protection, morphology dynamics at the cathode, amphibian presence of superoxide, and the roles of electrolyte. Bright prospects in further development of aprotic Na−O2 batteries are envisioned. [ABSTRACT FROM AUTHOR]

Nanostructured TiO2(B) suffers from severe initial irreversible capacity loss (ICL) (≥15 %), hindering its commercialization. While the incorporation of stable Li4Ti5O12 with negligible ICL into TiO2(B) should address the issue, the synthesis of TiO2(B)/Li4Ti5O12 composite remains unexploited because the conventional synthesis temperature required for the Li4Ti5O12 formation induces growth of anatase TiO2. Here, we achieve the first synthesis of TiO2(B)/Li4Ti5O12 nanocomposite by interfacing high‐energy (020) planes of TiO2(B) nanofibers and Li4Ti5O12 with a small lattice mismatch. As a new class of Li‐ion battery anode, the TiO2(B)/Li4Ti5O12 nanocomposite features a significantly mitigated initial ICL (7 % at 35 mA g−1), stable cycling (93 % capacity retention after 1000 cycles at 1750 mA g−1), and enhanced rate performance (122 mAh g−1 at 2630 mA g−1). This can be mainly attributed to the synergistic effect of the composition and structure resulting in reduced and stabilized SEI formation. Demonstrating the first success of synthesizing a TiO2(B)/Li4Ti5O12 composite, this work provides insights to the effective integration of compounds requiring high synthesis temperature with metastable phases. First synthesis of TiO2(B)/Li4Ti5O12 composite (TB‐LTO) achieved by interfacing high‐energy (020) planes of TiO2(B) nanofibers (TB) and Li4Ti5O12 with a small lattice mismatch; the composite mitigates initial irreversible capacity loss of TiO2(B) effectively; and demonstrates superior rate capability and cyclability. [ABSTRACT FROM AUTHOR]

An iron-nitrogen-doped core-shell mesoporous carbon support loaded with a RuO2 catalyst was used as a Li-O2 cathode. Corrosion and degradation problems were avoided by doping carbon with iron and nitrogen. Well-dispersed RuO2 in the hierarchical porous structure facilitated a reversible nanoscale solid-phase reaction. At 2.0 A g−1 (on the basis of catalyst plus carbon support), a capacity of 10 Ah g−1 was demonstrated with a discharge potential of 2.4 V and a corresponding recharge potential of 3.6 V. On the other hand, at 1.0 A g−1, the discharge and recharge potentials are maintained at 2.5 V and 3.5 V, respectively, over 50 cycles. [ABSTRACT FROM AUTHOR]

Solid-state reactions are a simple and scalable synthetic method, but they lack controlled nanostructures at present. Here, we report an energy-efficient solid-state synthesis, via the addition of carbon, to mass-produce uniform, single-crystalline, one-dimensional metal oxide nanorods with tunable composition according to performance demands. The carbon added in the solid-state reaction provides an alternative low-temperature route for the metal oxide formation due to the extra local heat generation and CO2/CO release from carbon oxidation. To demonstrate the methodology, a series of single-crystalline Na2Ti3O7/Na2Ti6O13 nanorods with tunable composition are synthesized and applied in sodium-ion batteries. The local heat generated from carbon allows formation of Na2Ti3O7 at 450 °C, a reaction temperature much lower than that of conventional solid-state methods (750-1000 °C), and Na2CO3 is regenerated to be recycled in the synthesis. The high theoretical capacity of Na2Ti3O7 and low volume expansion of Na2Ti6O13 upon charge-discharge are synergistically exploited to achieve high electrochemical performance and stability. [ABSTRACT FROM AUTHOR]

High surface area mesoporous Cr2O3 nanostructures are synthesized using MIL-101(Cr) as a sacrificial template in a combustion synthesis with the octahedral shape of the MOF retained. This new synthetic approach avoids a template-removal step, can be carried out in a simple device, and is time and energy efficient for easy scale-up. [ABSTRACT FROM AUTHOR]

Student interaction and formative assessment are two agendas which hold equal importance in guiding the student approach to learning in engineering and in many disciplines. With MCQs being a familiar assessment tool for most teachers, it would be ideal if there were a combined approach which involved using MCQ to assess formatively and at the same time, to encourage student engagement and in-class interaction. In this paper, we investigate a number of MCQ delivery methods which may be able to step up to both concerns. [ABSTRACT FROM AUTHOR]

Abstract: A series of experiments have been performed to investigate the effects of three electrolytes of different compositions (EO, EA and EM) on the electrochemical characteristics of MmNi3.55Co0.72Al0.3Mn0.43 hydrogen storage alloy electrode. Electrolytes EA and EM were obtained by adding appropriate amounts of Al2(SO4)3 and MnSO4 to the original electrolyte EO (6M KOH+1wt% LiOH), respectively. Electrode activation, maximum capacity, cycle life, self-discharge and high-rate discharge characteristics have been studied. It was found that a maximum capacity of about 260mAh/g has been obtained for the alloy electrodes in all these electrolytes after 5–7 cycles of charging/discharging. The alloy electrodes have a good durability in electrolytes EA and EM, especially after 175 cycles. Using the capacity retention as an indication of self-discharge resistance, almost identical degree of capacity retention (82% after 4 days and 45% after 16 days) has been observed at 298K, regardless of the electrolytes used. When tested at higher temperature, however, a higher capacity retention (46% after 3 days) at 333K has been observed for electrodes in electrolyte EA, and about 32% for electrodes in both electrolytes EO and EM. As to high-rate discharge behavior of the results of high-rate discharge tests indicated that about 50% of discharge efficiencies were obtained in the three electrolytes at 333K by continuous-model high-rate discharge method, at a discharge rate of 7C, and 22% in 298K. The alloy electrode in electrolyte EM has the best durability, in which about 50% of discharge efficiency at DC=9C was obtained by step-model high-rate discharge method at 333K, which was even higher than that at 298K. [Copyright &y& Elsevier]

Abstract: A comparison is made of the electrochemical and structural properties of LaNi4.25Al0.75 alloys in thin film and powder forms. X-ray diffraction (XRD) revealed that both the LaNi4.25Al0.75 thin film and powder materials are crystalline. Atomic force microscopy (AFM) and focused ion beam microscopy (FIB) proved that the film appeared to have a hill-like surface morphology, but was rather dense with a thickness of about 4.2 μm. Simulated battery tests indicate that both exhibit similar electrochemical behavior, possibly due to their crystal structure, as it requires a primary activation to reach its fully active state. However it took a longer activation period for the film to be activated; an apparent initial decrease of charging voltage with cycle number was observed, as were abnormal discharge processes during activation. After 30 charge/discharge cycles, small needle-shaped aluminium oxide particles were formed on both the powder and film surfaces. [Copyright &y& Elsevier]

Hydrogen released from ammonia borane in MIL-101(Cr) can be significantly improved by the attached amino and amide groups. The release with minimum impurities starts at 68 °C, reaching 1.6 equivalent of ammonia borane at 85 °C for the amino modified MOFs (NH2-MIL-101). [ABSTRACT FROM AUTHOR]

Abstract: Performance characteristics of a three electrolyte rechargeable acid–alkaline hybrid battery using a PbO2 positive plate and a nickel metal hydride (NiMH x ) negative electrode in separate electrolyte of H2SO4 and KOH were studied. This hybrid battery has three electrolytes in a single cell. A neutral K2SO4 salt solution was placed between the acid and alkaline compartments of the cell, in which a cation exchange membrane and an anion exchange membrane, were employed to separate these three electrolytes. The open circuit voltage of this hybrid cell was found to be 2.64V in an electrolyte configuration of 1M H2SO4|0.2MK2SO4|2M KOH electrolyte configuration, compared to 1.92V in the conventional lead-acid cell in 1M H2SO4 and 1.40V in a NiMH x cell in 2M KOH. This hybrid acid–alkaline PbO2/NiMH x battery was shown to operate with a voltage 20% higher than the conventional lead acid battery and 110% higher than nickel–metal hydride battery at 1/3C discharging rate. The concentrations of the three electrolytes, the dimension of the electrolyte chamber, and other cell/operation parameters with impacts on the hybrid cell performance were investigated. [Copyright &y& Elsevier]

Conventional ion-exchange polymeric membranes have limited selectivity due to their nonuniform and unstable structures. The rigid, regular, high porosity of metal organic framework (MOF) generally provides MOF membrane with exclusion/sieving effect but lack of electrostatic screening. Here we report for the first time a nonbiological highly selective MOF membrane with polyelectrolyte threaded in the nanochannel of metal organic framework (polyelectrolyte∼MOF) and its selective transport of alkali metal cations. Poly(sodium vinyl sulfonated- co -acrylic acid)∼MIL-53(Al) is prepared on anodic aluminum oxide substrate via steps of MOF MIL-53(Al) growth followed by in situ polymerization. The poly(VS- co -AA)∼MIL-53(Al) membrane demonstrates highly specific selectivity in transport of alkali metal cations. Rate of ion transport correlates inversely with the hydrated diameter of the ion reaching a low limiting rate near 0.7 nm hydrated diameter. Charge exclusion is demonstrated with blockage of anion transport under a concentration gradient. The highly uniform porous nanostructure of MOF and ionic function of polyelectrolyte offers the MOF membrane with synergistic selectivity based on exclusion forces of the framework and Coulomb forces from fixed charges of polyelectrolytes in nanochannels.

This article describes a novel method for depositing a dense, high quality palladium thin film via a one-step aqueous combustion process which can be easily scaled up. Film deposition of Pd from aqueous solutions by conventional chemical or electrochemical methods is inhibited by hydrogen embrittlement, thus resulting in a brittle palladium film. The method outlined in this work allows a direct aqueous solution deposition of a mirror-bright, durable Pd film on substrates including glass and glassy carbon. This simple procedure has many advantages including a very high deposition rate (>10 cm 2 min -1 ) and a relatively low deposition temperature (250 °C), which makes it suitable for large-scale industrial applications. Although preparation of various high-quality oxide films has been successfully accomplished via solution combustion synthesis (SCS) before, this article presents the first report on direct SCS production of a metallic film. The mechanism of Pd film formation is discussed with the identification of a complex formed between palladium nitrate and glycine at low temperature. The catalytic properties and stability of films are successfully tested in alcohol electrooxidation and electrochemical oxygen reduction reaction. It was observed that combustion deposited Pd film on a glassy carbon electrode showed excellent catalytic activity in ethanol oxidation without using any binder or additive. We also report for the first time the concept of a reusable "catalytic flask" as illustrated by the Suzuki-Miyaura cross-coupling reaction. The Pd film uniformly covers the inner walls of the flask and eliminates the catalyst separation step. We believe the innovative concept of a reusable catalytic flask is very promising and has the required features to become a commercial product in the future.

A porous metal-organic framework composite with flexible anion-exchange polymers threaded within the host cavity demonstrates very fast and reversible ion-exchange activity. Polyvinyl benzyl trimethylammonium hydroxide (PVBTAH) caged in ZIF-8 is synthesized in steps of chloro-monomer impregnation, in situ polymerization, amination, and alkaline ion exchange. The synthesized non-cross-linked PVBTAH∼ZIF-8 material exhibits superior ion-exchange kinetics compared to conventional ion-exchange resins.