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We report our facile and efficient approach for synthesizing Co-Fe alloy based oxygen reduction reaction (ORR) catalysts, in which alloy nanoparticles are encapsulated in nitrogen-doped carbon nanostructures. The catalysts with high hierarchical porosities are fabricated at an appropriate temperature of 775 °C without a further acid leaching treatment after pyrolysis due to the use of ZnO nanoparticles as auto-removable templates. Co/Fe atomic ratio is found to greatly influence the ORR catalytic activity. The catalyst with Co/Fe = 1 exhibits the best catalytic performance by showing an ORR onset potential of 0.99 V and a half-wave potential of 0.87 V (vs. RHE) in 0.1 M KOH, as well as 0.98 V and 0.83 V (vs. RHE) in 0.5 M H 2 SO 4 , better than or approaching the performance presented by a commercial 28.6 wt% Pt/C catalyst. The Zn-air battery using the synthesized CoFe@N-C catalyst delivers a higher power density at ambient conditions by air-breathing than the one using the 28.6 wt% Pt/C catalyst. Relatively higher atomic concentrations of both Fe and Co as well as more graphitic nitrogen in the surface of CoFe@N-C detected by X-ray photoelectron spectroscopy (XPS) may account for its excellent ORR catalytic activities both in alkaline and acidic environments. • E onset = 0.98 V and E 1/2 = 0.83 V (vs. RHE) in 0.5 M H 2 SO 4. • Using ZnO as an auto-removal template. • a strong dependence of ORR activity on Co/Fe ratio in the catalysts. • the catalyst with Co/Fe= 1 offers the best ORR activity. • high surface metal concentrations account for the high ORR activity. [ABSTRACT FROM AUTHOR]

Objectives Due to the increasing prevalence of drug-resistant S taphylococcus aureus infection, we develop novel 4-hydroxycoumarin derivatives as antimicrobials. Methods The antibacterial activity of 4-hydroxycoumarin derivatives against drug-susceptive S . aureus ( ATCC 29213) and methicillin-resistant S . aureus ( MRSA) were evaluated using minimal inhibitory concentration ( MIC) assay; the activity of favourable compound was further observed using bacterial growth curves assay and in the MRSA infection mice. Key findings Compared with dihydropyran derivatives, compound 1 as one of biscoumarins showed most potent activity with MIC values of 4-8 μg/ml and apparently inhibited the growth rate of S . aureus ATCC 29213 and USA300 strain in concentrations of both 16 and 32 mg/ml. In the mice infected with MRSA USA300, administration of 5 mg/kg compound 1 improved the animal survival rate to 66.7%, and improved the pathological change in lung tissue compared with the infection model animals. No significant cytotoxicity of compound 1 was observed on the umbilical vein endothelial cells ( HUVECs) under the concentration of 800 μg/ml. Conclusion Compared with the dihydropyran derivatives, biscoumarins exhibited more promising activity against both drug-sensitive and drug-resistant S . aureus, and it is efficacious in treating MRSA infections in mouse models with a favourable safety in human cells. [ABSTRACT FROM AUTHOR]

• Thermally stable La-Ni-B composites were synthesized. • La-Ni-B composites consisted of amorphous La-B-O and Ni-B. • High and stable catalytic performance for dehydrogenation of MgH 2. • La-incorporation effectively inhibited crystallization and growth of Ni. In this work, we synthesized La-incorporated Ni-B amorphous composites and investigated their effects on enhancing dehydrogenation/hydrogenation properties of MgH 2. MgH 2 with 5 wt% 2La-3Ni-B demonstrated significantly improved dehydriding kinetics. About 6.0 wt% hydrogen could be released within 5 min at 300 °C. Moreover, no decrease in deydrogenation rate was observed within ten cycles. XRD, XPS, SEM and HRTEM examinations revealed that the La incorporation into Ni-B resulted in an amorphous La-B-O structure that could keep its disorder state up to 600 °C. The crystallization and growth of Ni dispersed in the La-B-O structure was significantly retarded. Also the alloying of Mg with Ni or La was not observed. As a result, the added La-Ni-B composites showed higher structural and catalytic stability than Ni-B during hydriding/dehydriding cycling of MgH 2 at high temperatures. [ABSTRACT FROM AUTHOR]

Abstract: A series of M-doped polypyrrole (PPy)-modified BP2000 catalysts (M=Mn, Fe, Co, Ni, and Cu) are synthesized using the hydrothermal method. The synergy among a transition element, nitrogen, and carbon for oxygen reduction reaction (ORR) in alkaline medium is discussed based on the physical characterization and electrochemical analyses of the Co-doped PPy-modified BP2000. PPy is found to adhere carbon black particles together to form a porous 3D network during the PPy modification on BP2000. PPy reconfiguration occurs during the hydrothermal treatment process. The individual interactions between BP and PPy, BP and Co, and Co and PPy exhibit insignificant effects on the enhancement of ORR. The cooperative interaction among Co, N, and C plays a very important role in the enhancement of ORR. The doping effect of transition-metal salt on ORR enhancement depends on the nature of the transition element and the corresponding anion. [Copyright &y& Elsevier]

Abstract: The present study reports on the promotion of methanol oxidation on Pt using UV–vis light irradiation. The anodic current rapidly responds to UV–vis light irradiation, and the rise and fall of the anodic current coincide with intermittent light irradiation during MeOH electrooxidation at various potentials. This photochemical effect depends on the applied potential and the wavelength of the applied UV–vis light. Irradiation with a short wavelength produces a more pronounced photochemical effect. The enhancement of CO electrooxidation with the aid of the oxygen-containing species formed on the Pt catalyst under UV-light irradiation plays an important role in the promotion of methanol oxidation. [Copyright &y& Elsevier]

Abstract: Carbon-supported Co(OH)2 and Ni(OH)2 catalysts are prepared to examine the mechanism of oxygen reduction reaction (ORR) on hydroxide catalysts. ORR via the 4-electron transfer pathway on a hydroxide undergoes oxidation of hydroxide by O2 to form oxyhydroxide, followed by electrochemical reaction of oxyhydroxide to regain hydroxide. β-Ni(OH)2 has the same crystal structure and lattice parameters as β-Co(OH)2, but it exhibits a poorer catalytic activity toward ORR than β-Co(OH)2 at a low temperature. The poor catalytic activity of Ni(OH)2/C can be attributed to the difficulty in Ni(OH)2 oxidation and the slow kinetics of NiOOH electroreduction to Ni(OH)2. The catalytic activity of the Ni(OH)2/C catalyst is significantly improved through elevating the operation temperature because Ni(OH)2 oxidation to NiOOH and NiOOH electroreduction are improved at a high temperature. A model of ORR via the 4-electron transfer pathway on transition metal hydroxides is suggested and discussed. [Copyright &y& Elsevier]

Abstract: A carbon nanotubes (CNTs) supported composite catalyst consisting of Pd and Ni (Pd–Ni/CNT) is synthesized by a chemical method. The electrocatalytic activities of Pd/CNT, Ni/CNT and Pd–Ni/CNT toward the hydrazine oxidation reaction (HOR) are evaluated by linear sweep voltammetry, electrochemical impedance spectroscopy and polarization measurement. The composite catalyst demonstrates higher electrocatalytic activity than its single-constituent catalysts due to the synergy between Ni and Pd. The Pd addition in the composite catalyst prevents oxidation of Ni so that the Pd–Ni/CNT electrode exhibits smaller reaction resistance to the HOR than the Ni/CNT and Pd/CNT electrodes. [ABSTRACT FROM AUTHOR]

Abstract: Mg and Mg-based alloys are not only promising hydrogen storage materials due to their high storage capacities, but also potential reducing agents in the synthesis of sodium borohydride NaBH4, an attractive hydrogen source with 10.6wt% hydrogen content. In this study, the MgH2 formation kinetics in pure Mg and Mg–23.5wt% Ni was studied and correlated with NaBH4 synthesis kinetics. It was found that the hydriding kinetics of Mg–23.5wt% Ni was significantly improved owing to the fine laminar Mg/Mg2Ni structure. Ballmilling and surface treatment made the eutectic alloy absorb 2.0wt% hydrogen at 353K. When these materials were applied for the NaBH4 synthesis, it was found that the eutectic Mg–Ni alloy enhanced the NaBH4 formation kinetics at high temperatures. However, NaBH4 was not produced at 353K although MgH2 could be formed. [Copyright &y& Elsevier]

Abstract: Hydrolysis of sodium borohydride NaBH4 is a promising method for on-board hydrogen supply for fuel cells. In this study, the hydrolysis reaction was studied by starting with solid NaBH4 rather than aqueous borohydride solutions, and adding less amount of water in an attempt to explore the maximum hydrogen generation capacity. It was found that hydrogen could be liberated at very high rates and over than 90% conversion rates were achieved when the mole ratio of water to sodium borohydride was not less than 4:1. The final hydrogen generation capacity was achieved as high as 6.7wt%. Materials such as CoCl2 or cobalt powder were found to be effective as the catalysts for the hydrolysis reaction at such reaction conditions. A large heat effect due to the exothermic reaction and a low melting point of NaBO2·4H2O led to the acceleration of hydrogen generation at the latter part of the hydrolysis process. It is thus promising to utilize these reaction conditions to achieve high hydrogen generation capacity by proper system design. [Copyright &y& Elsevier]

Abstract: The performance stability of the direct borohydride fuel cell (DBFC) working under passive conditions was studied in this work. The stability within hours was found to be greatly affected by mass transport properties of different cell components. It was significantly improved by modifying electrode structures, increasing hydrophobicity of the cathode and using pretreated membranes. On the other hand, the stability of the DBFC cell for more than 100h was determined by the durabilities of these cell components. The nickel anode and silver cathode were found to degrade after prolonged operations and thus the durabilities of these non-noble metal catalysts need to be improved. [Copyright &y& Elsevier]

Abstract: In this work, we suggested a figuration of the direct hydrazine fuel cell (DHFC) using non-precious metals as the anode catalyst, ion exchange membranes as the electrolyte and alkaline hydrazine solutions as the fuel. NaOH addition in the anolyte effectively improved the open circuit voltage and the performance of the DHFC. A power density of 84mWcm−2 has been achieved when operating the cell at room temperature. It was found that the cell performance was mainly influenced by anode polarization when using alkaline N2H4 solutions with low NaOH concentrations. However, when using alkaline N2H4 solutions with high NaOH concentrations as the fuel, the cell performance was mainly influenced by cathode polarization. [Copyright &y& Elsevier]

Abstract: Direct borohydride fuel cell (DBFC) as a liquid type fuel cell is promising for portable applications. In this study, we report our recent progress in the micro-fuel cell development. A power density of 80mWcm−2 was achieved in passive mode at ambient conditions when using the anode containing nickel, carbon-supported Pd catalyst and Nafion ionomer. Current efficiency was also found to be greatly increased due to the use of Nafion rather than polytetrafluoroethylene (PTFE). Based on improvements on single cell performance, planar multi-cell power modules were assembled to study the feasibility of making high-performance and practical DBFC power units. A power of 2.5W was achieved in a fully passive eight-cell module after significantly simplifying cell structure. [Copyright &y& Elsevier]

Abstract: Borohydrides, a group of compounds with large hydrogen contents, can generate hydrogen readily by their hydrolysis reaction. In this study catalysts based on nickel and cobalt were developed to accelerate the hydrolysis reaction for hydrogen generation. Catalysts in four forms were tested for each metal: fine metal powder, metal salt, metal boride and Raney metal. It was found that the hydrolysis reaction was primary a zero-order reaction under the catalysis of these catalysts. Although cobalt showed higher catalytic activity than nickel in most cases, Raney Ni exhibited almost the same activity as the Raney Co. Among four chemical forms for nickel, Raney Ni demonstrated the best performance. Moreover, Raney catalysts made from alloys of nickel and cobalt showed even higher activity. The reaction on Raney metals was also characterized by a slowdown in hydrogen generation rate at low borohydride concentrations because of a mass transfer limitation. [Copyright &y& Elsevier]

Anodic performances of alkali borohydrides on several electrocatalysts such as Ni, Raney Ni, Pd, Pt, Cu, Au have been studied in an effort to develop suitable electrode materials for a borohydride-fueled fuel cell. The open-circuit potentials (OCPs), polarization performances, and hydrogen evolution behaviors were examined in a three-electrode system. The open-circuit potential was found to be dependent on borohydride concentration and also influenced by the electrocatalyst. In concentrated borohydride solutions used in this work, electrode polarizations were less influenced by the fuel concentration. Borohydrides on different electrocatalysts showed different hydrogen evolution behaviors. The relation of hydrogen evolution rate with the anode current was found to change not only with the concentration of borohydride and but also with the electrode material. Comparison of anodic behaviors of borohydride on different electrodes implies that the anodic oxidation of borohydride, as a multi-step process, may take different reaction paths, depending on the electrocatalyst and reaction conditions such as the borohydride concentration. [Copyright &y& Elsevier]

A convenient method was developed to synthesize potassium borohydride by a mechano-chemical reaction of saline hydrides with dehydrated borates with a planetary ball mill. Among the tested saline hydrides, MgH2 was the most effective reactant for borohydride formation. In order to improve the borohydride yield, it was necessary to add an excessive amount of MgH2. When a 35% excess of MgH2 was added, potassium borohydride yield reached 100%. The borohydride formation was strongly dependent on the water content in reactants. When the water content in KBO2 samples was over 24.8 wt.% (equivalent to KBO2·1.5H2O), no borate was converted into borohydride by the mechano-chemical reaction. [Copyright &y& Elsevier]

In order to enhance the effect of fluorination treatment (F-treatment) on charge–discharge characteristics of AB2-type Laves phase alloys, three pulverization methods were applied for the F-treated alloys; e.g. hydriding–dehydriding, dry ball-milling and wet ball-milling. As a result, it was found that the F-treated alloy powder obtained by the wet ball-milling had smaller particle size and larger specific surface area than those obtained by the other two methods. The F-treated alloy electrode prepared from the alloy powder obtained by the wet ball-milling showed good initial activation, high-rate dischargeability and relatively high discharge capacity. These results indicate that the wet ball-milling is a very effective pulverization method in enhancing the effect of the F-treatment. [Copyright &y& Elsevier]

Abstract: Alkaline sodium borohydride solutions are potential hydrogen sources for fuel cells. Thermal properties of the NaBH4–NaOH–H2O ternary system were measured by DSC and temperature-rise calorimetry. Liquidus temperatures showed that it is possible to store and use the solutions well below 0°C if NaOH concentration is less than 20wt%. The solubility of sodium borohydride was found to be large in these solutions, but decreased with increasing NaOH concentration. The optimum composition for alkaline borohydride solutions seems to be 15wt% NaBH4 in 10wt% NaOH considering both the liquidus temperature and hydrogen storage density. [Copyright &y& Elsevier]

The homogeneous/heterogeneous catalyst combination of VO2+ in anolyte with Pd/C at the anode is first introduced in a formic acid fuel cell to enhance HCOOH electrooxidation. The VO2+/Pd catalyst combination establishes a stepwise reaction pathway involving HCOOH dehydrogenation to form V3+ from VO2+ reduction and subsequent V3+ electrooxidation to regain VO2+. The fuel cell with the VO2+/Pd combination presents a peak power density of 341.3 mW cm−2 and stable power density higher than 30 mW cm−2. [ABSTRACT FROM AUTHOR]

In this study, a SnO 2 based composite composed of SnO 2 nanoparticles, reduced graphene oxide (rGO) and polyaniline (PANI) sheets was synthesized and evaluated as the anode material of high performance Li-ion batteries. The rGO/SnO 2 /PANI composite exhibited excellent electrochemical performance including high capacity (1017 mAh g − 1 at 200 mA g − 1 for the 2nd cycle), superior rate capability (397 mAh g − 1 at a current density of 10 A g − 1 ) and cyclic stability (1280 mAh g − 1 after 200 cycles). The significant enhancements in electrochemical performance are ascribed to the nanostructure of the composite in which SnO 2 nanoparticles of around 3.9 nm were most probably sandwiched between rGO and PANI sheets that are flexible and conductive. Extremely fine SnO 2 nanoparticles, high specific surface area, mesoporous structure and good electrical conductivity of the composite resulted in the high capacity and superior rate performance. The nanostructure of rGO/SnO 2 /PANI can accommodate volume expansion during lithiation of SnO 2 and at the same time inhibit particle aggregation during cycling, yielding excellent cyclic stability of the rGO/SnO 2 /PANI composite. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we explored the possibility of NaBH4 synthesis when Mg reacted with hydrous sodium borates under hydrogen. It was found that Mg could react with the water in molten hydrous borates to form MgO and release hydrogen, which can be used for NaBH4 synthesis. Then remained Mg would react with formed anhydrous borate to form NaBH4. NaBO2 conversion rate was decreased with increase of the crystalline water content in the hydrous sodium borates. Based on experimental results, a mechanism of NaBH4 formation when Mg reacted with hydrous sodium borates was suggested. [Copyright &y& Elsevier]

Abstract: In this work, influences of Na2O in compounds lying within the Na2O–NaBO2 composition domain on NaBH4 recovery have been investigated. It is found that Na2O plays different roles in NaBH4 formation. Na2O is beneficial in terms of NaBH4 formation and reaction kinetics when Al is used for NaBH4 recovery, but harmful to NaBH4 formation when Mg is used for NaBH4 recovery from compounds lying within the Na2O–NaBO2 composition domain. High borate conversion rates can be obtained when Mg reacts with compounds lying within the Na2O–NaBO2 composition domain with less Na2O or Al reacts with the compounds containing more Na2O. NaBH4 formation temperature depends upon the used metals. [Copyright &y& Elsevier]

In this study, we synthesized ZrO 2 nanorods through a hydrothermal process as a catalyst precursor for the reversible hydrogen storage reaction between 2LiH + MgB 2 and 2LiBH 4 + MgH 2. The 2LiH + MgB 2 composites doped with the ZrO 2 nanorods demonstrated superior and stable hydriding/dehydriding kinetics upon cycling. The XRD, SEM and HRTEM results revealed that the doped ZrO 2 nanorods were transformed into ZrB 2 nanoparticles with a size of a few nanometers during the first hydrogenation. The initial nanosize of the ZrO 2 catalyst precursor accounted for the formation of extremely fine ZrB 2 nanoparticles, which acted as heterogeneous nuclei of MgB 2 . The present study provides a new route for performance enhancement of complex hydride composites through manipulating the nanostructure of catalysts. [ABSTRACT FROM AUTHOR]

Abstract: In this study, Fe3O4/carbon nanocomposites as anode materials of Li-ion batteries were synthesized through heating hierarchically porous Fe-based xerogels under N2 atmosphere. The pyrolysis of amorphous Fe-xerogel base materials resulted in the simultaneous formation of Fe3O4/C composites, in which Fe3O4 particles of less than 50nm were uniformly dispersed and embedded in a porous carbon matrix. Due to the favorable nanostructure, the synthesized Fe3O4/C composites with a proper carbon content of 18.8wt.% exhibited good electrochemical performance including high capacity and rate capability as well as much enhanced cyclic stability. [Copyright &y& Elsevier]

• Poor hydrocarbon diffusion against CO 2 evolution leads to poor anode performance in DLFCs. • Reaction-separation anode features distinct pathways for hydrocarbon diffusion and CO 2 release. • CO 2 pathway is built by the hydrophobic catalyst layer and gas diffusion layer. • Hydrocarbon pathway is built by the hydrophilic catalyst layer and liquid diffusion layer. • The FAFC with the reaction-separation anode presents a power density as high as 433.5 mW cm−2. Direct liquid-feed fuel cells (DLFCs) have been considered as a potential power candidate for portable electronic devices and electric vehicles. However, evolution of CO 2 arising from hydrocarbon electrooxidation leads to a great diffusion resistance of hydrocarbon in anode, seriously retarding the anode process of DLFCs. Herein, this work suggests a reaction-separation anode to separate gaseous CO 2 from liquid anolyte to decrease polarization, using the formic acid fuel cell (FAFC) as an example of the DLFCs. The reaction-separation anode is composed of hydrophilic and hydrophobic components. The hydrophilic component includes a Nafion-based catalyst layer and a liquid diffusion layer contacting to the membrane. The hydrophobic component includes a poly(tetrafluoroethylene)-based catalyst layer and a gas diffusion layer contacting to the flow-field of anode plate. The hydrophilic component provides the anolyte diffusion pathway while the hydrophobic component enhances the CO 2 release. Such a reaction-separation anode with configuration of the liquid-diffusion-layer/hydrophilic-catalyst-layer/hydrophobic-catalyst-layer/gas-diffusion-layer shows small polarization, presenting excellent anode performance. A power density as high as 433.5 mW cm−2 is achieved when using a vanadyl sulfate-contained formic acid anolyte as the fuel to run the FAFC with the reaction-separation anode. This innovative anode makes a significant progress in development of FAFC technology, shedding a light on the resolution of the mass transfer difficulty in the anode of DLFCs. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of cobalt-doped catalysts (Co–PPy/BP) is synthesized by hydrothermal treatment of polypyrrole-modified BP2000 in cobalt nitride solution. The hydrothermal temperature is varied from 80 °C to 180 °C to investigate the effect of treatment temperature on the catalytic site formation for oxygen reduction reaction (ORR). Treatment temperature is found to slightly affect the structure and morphology of the synthesized catalysts. However, the catalytic activity of the synthesized Co–PPy/BP increases with increased treatment temperature up to 160 °C because higher treatment temperatures promote pyrrolic-N conversion to Co–Nx. Co–Nx catalyzes H2O2 electroreduction reaction, which increases the number of electrons transferred during ORR. However, the hydrothermal treatment at 180 °C leads to decreased pyrrolic-N and Co–Nx contents, which results in decreased catalytic activity of the synthesized Co–PPy/BP. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we report the preparation and electrochemical evaluation of LiFePO4-carbon nanocomposites with carbon aerogels of varied pore size and distribution. In these composites, LiFePO4 nanoparticles smaller than 50nm are confined to a three-dimensional (3D) microporous network that functions as the electronic and ionic conductor. The pore size of carbon aerogel is adjusted to achieve smaller LiFePO4 nanoparticles. The KOH activation treatment of carbon aerogels is used to increase micropores that act as electrolyte reservoirs and is beneficial for ionic conductivity. Additional carbon coating of LiFePO4 particles using glucose further enhances the electrode performance. The resultant composite electrodes exhibit superior rate performance and good cyclic stability due to the optimized nanostructure. The nanocomposites of LiFePO4 and carbon areogels provide good examples of material nano-engineering owing to their tunable nanostructures. [Copyright &y& Elsevier]

Abstract: A comparative study was performed on four LiBH4-based hydrogen storage composites 2LiBH4 + MgX2 and 6LiBH4 + CaX2 (X = H and F). The composites with fluorides and those with corresponding hydrides exhibited similar hydrogen storage properties. The dehydrogenation of 2LiBH4 + MgF2 demonstrated a strong dependence on the hydrogen back pressure, similar to that of 2LiBH4 + MgH2. The reversible hydrogen storage of 2LiBH4 + MgF2 was achieved under a back pressure of 5 bar at 450 °C. Dehydrogenation under lower H2 pressures resulted in the production of Mg and thus a partial reversibility. In contrast, both 6LiBH4 + CaH2 and 6LiBH4 + CaF2 revealed reversible hydrogen storage properties regardless of the hydrogen back pressure. The structural difference between MgB2 and CaB6 may account for the observed differences in hydrogen storage properties of the Mg- and Ca-containing LiBH4 reactive composites. [Copyright &y& Elsevier]

Abstract: The mixtures of LiBH4 with halides of Ce or La in a molar ratio of 3:1 were investigated to explore their hydrogen storage properties. The ball milling of LiBH4 with chloride of Ce or La yielded Ce(BH4)3 and La(BH4)3, while fluoride of Ce or La did not react with LiBH4 during extended ball milling at room temperature. The dehydrogenation temperatures of the ball-milled mixtures were reduced to 220–320°C, which were much lower than that of pure LiBH4. The diborane emission during hydrogen release was observed at a low level. The dehydrogenation temperature is found to be affected by the composition of rare earth halides, but less influenced by ball milling time. The endothermic dehydrogenation reactions produced lithium halides, hydrides and borides of the corresponding rare earth element. Moreover, the LiBH4 +1/3(Ce, La)(Cl, F)3 showed partial reversibility through the formation of an unknown borohydride, allowing for a potential hydrogen storage system. [ABSTRACT FROM AUTHOR]

Abstract: The fuel efficiency of borohydride electro-oxidation on carbon-supported Au and Ag electrodes was found to be highly dependent on the concentration ratio of [OH−]/[BH4 −] in the solution. Near-8e reactions occurred when [OH−]/[BH4 −]≥5. However when [OH−]/[BH4 −] was smaller than 5, hydrogen gas was evolved and the fuel efficiency was reduced. Only 3e reaction stoichiometry was obtained at [OH−]/[BH4 −]=1. Detailed cyclic voltammetry (CV) studies revealed that both the Au/C and Ag/C showed different anodic waves in varied NaOH–NaBH4 solutions. The CV analysis results suggest that BH3OH−, an intermediate possibly produced by homogeneous hydrolysis, is responsible for the electrochemical reaction at [OH−]/[BH4 −]=1. Comparison of CV voltammograms in borohydride solutions with that in the H2-bubbled NaOH solution suggests that borohydride electro-oxidation on Au or Ag electrode is through direct BH4 − oxidation rather than through a hydrogen ionization mechanism. It is concluded that there exists an inherent competition between two oxidizing species of OH− and H2O during borohydride electro-oxidation, that is, if accessible OH− ions are not sufficient for each BH4 − to accomplish the 8e electro-oxidation, part of BH4 − will react simultaneously with H2O to generate hydrogen. [Copyright &y& Elsevier]

LaB 6 is a unique plasmonic material, for which the localized surface plasmon resonance (LSPR) absorption band intrinsically lies in the near infrared (NIR) region. In this work, we synthesized spherical LaB 6 nanoparticles with a tunable size within 50–200 nm. The optical properties of these LaB 6 nanospheres were found to be sensitive to the thickness of surface oxide layer that was formed during the synthesis, purification and dispersion processes. In order to enhance the stability of LaB 6 nanoparticles in aqueous environment, LaB 6 @SiO 2 with a core-shell structure was successfully prepared. Both LaB 6 and LaB 6 @SiO 2 demonstrated low cytotoxity in biomedical tests when their concentrations were limited to 0.2 mg mL−1. The in vitro photothermal therapy experiment showed that 4T1 cancer cells were eventually apoptotic after being exposed to a 980 nm laser for 5 min at a considerably low power density of 0.82 W cm−2 and a low dose of 0.1 mg mL−1 for LaB 6 @SiO 2. The results suggest that these LaB 6 nanospheres are viable photothermal agents for biomedical applications. • Spherical LaB 6 nanoparticles were chemically synthesized. • The NIR light absorption of LaB 6 was sensitive to the surface oxide layer. • Core-shell LaB 6 @SiO 2 was prepared for biomedical compatibility. • Low concentrations of LaB 6 and LaB 6 @SiO 2 were biosafe. • LaB 6 @SiO 2 was effective agent for photothermal therapy. [ABSTRACT FROM AUTHOR]

This research presents a new insight into MOFs-derived materials with oriented macropores and ultrahigh specific surface area. The oriented-macroporous-carbon (OMC) incorporated with γ-Al 2 O 3 is prepared through pyrolysis of a glucose-urea-resin-filled MOF MIL-53 with double templates of NaCl-KCl eutectic and nano-CaCO 3 . The glucose-urea resin and NaCl-KCl eutectic fill the tunnels in the MIL-53 to avoid tunnel collapse and combination during pyrolysis. The nano-CaCO 3 stays out of the tunnels to prevent from forming sealed tunnels. The synthesized OMC exhibits excellent polysulfide absorption capability, ascribed to its ultrahigh specific surface area and the co-existence of active O and N sites for polysulfide absorption. The resultant sulfur electrode shows much high discharge capacity, long life, and excellent rate performance. An initial capacity of 1626 mAh g −1 at 0.05 C and a rate capacity as high as 430 mAh g −1 at 10 C are achieved. A reversible capacity of 850 mAh g −1 is retained after 300 cycles at a discharge rate of 0.2 C. [ABSTRACT FROM AUTHOR]

Two N-containing hydrocarbon based polymers polyacrylonitrile (PAN) and polyaniline (PANI) were found to be able to destabilize LiBH 4 , a potential hydrogen storage material, resulting in larger hydrogen capacities of more than 10 wt% with peak dehydrogenation temperatures around 344 °C. The results suggest that a co-destabilization effect was achieved through the interaction of B H and C H bonds, which was further enhanced due to the presence of nitrogen atoms in polymers. After rehydrogenation of the dehydrogenated products, LiBH 4 was found to be regenerated to a large extent in both of the LiBH 4 +polymer composites. Detailed analysis including XRD, FTIR, DSC-TG-MS, HRTEM, Raman, XPS and solid-state 11 B MAS NMR was performed to elucidate the dehydrogenation and rehydrogenation mechanisms in these composites. The results provide considerable information about interaction mechanisms among B H, C H, N H and C N bonds and also shed lights on the enhancement of LiBH 4 dehydrogenation and reversibility. [ABSTRACT FROM AUTHOR]

• Flake S 8 and Li 2 S nucleate on polar surface but island-like ones on apolar surface. • By-path deposition aggravates Li 2 S segregation leading to capacity decay. • Interaction of Li-shunt growth and Li 2 S segregation causes rapid cathode failure. • Areal capacity of 24.6 mAh cm−2 and energy density of 47.9 mWh cm−2 are achieved. Active-substance (S 8 and Li 2 S) deposition layer formed on polar interfaces is more reactive than that formed on apolar interfaces. However, when deposition layer reaches a certain thickness, by-path active-substance deposition takes place because of polysulfide disproportionation, which aggravates active-substance segregation to decrease the reactivity. This leads to a significant capacity decay and failure to accomplish polysulfide delithiation after certain cycles, which is understood as the results of decreased active-substance utilization and formed local micro-short-circuits, respectively. The finding of correlation between active-substance segregation and cathode deterioration inspires the design of polytetrafluoroethylene-based self-supported cathode to suppress active-substance segregation through avoiding increase of interphase contact resistance during cycling. With S-loading of 4.0 mg cm−2, the as-prepared cathode demonstrates excellent cycleability, retaining a capacity of 300 mAh g−1 at a rate of 2C after 1000 cycles. When increasing S-loading up to 36.5 mg cm−2, the as-obtained cathode delivers an ultra-high areal capacity of 24.6 mAh cm−2 after 100 cycles at 0.1 C. However, increasing S-loading aggravates Li 2 S segregation which then narrows down Li+ transportation, leading to formation and growth of Li-shunts which in turn stimulates active-substance segregation. Such an inductive interaction between Li-shunt growth and active-substance segregation results in the fast formation of local micro-short-circuits, causing the constant supply of Li from Li shunts to cathode, and eventually accelerating cathode deterioration. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, hydrogen release and uptake properties for composites of LiBH 4 with the conjugated polymer poly( p -phenylene) (PPP) were investigated. The incorporation of LiBH 4 with PPP led to a significant destabilization effect, decreasing the dehydrogenation temperature of LiBH 4 by 100 °C. Moreover, LiBH 4 could be regenerated at 450 °C under 9.0 MPa H 2 . By thorough analyses using XRD, HRTEM, FTIR, Raman, XPS as well as 11 B MAS NMR, the dehydrogenation product of LiBH 4 +PPP and the regeneration mechanism of LiBH 4 are elucidated. Also the reason of capacity degradation is discussed based on the analysis results. The formation condition of LiBH 4 was significantly moderated due to the presence of a simultaneously formed amorphous mixture of boron and carbon, which sheds light on the improvement of LiBH 4 reversibility. [ABSTRACT FROM AUTHOR]

In this study, we report a novel and facile synthesis approach of boron-rich transition metal borides such as LaB 6 and TiB 2 through reaction of lithium borohydride (LiBH 4 ) with corresponding metal hydroxide or oxide at temperatures below 600 °C. A fast endothermic reaction occurred at around 350 °C in the ball milled mixture of 6LiBH 4 + La(OH) 3 or 12LiBH 4 + La 2 O 3 , efficiently producing crystalline LaB 6 nanoparticles of a size smaller than 100 nm. In comparison, the reaction of LiBH 4 with TiO 2 proceeded within a wide temperature range from 120 °C to 500 °C, resulting in the formation of nanocrystalline TiB 2 of only a few nanometers. This synthesis method proved to be a facile and general route to fabricate nanosized transition metal borides. [ABSTRACT FROM AUTHOR]

A novel method of in-situ catalytic site (CoN x ) construction in macroporous carbon (MPC) is developed. The nitrogen-containing MPC-supported cobalt (Co/N–MPC) catalysts are synthesized via the pyrolysis of a mixture of glucose-urea resin, nano-CaCO 3 , and cobalt nitrate. The nano-CaCO 3 functions as a template to fabricate MPC that provides high electric conductivity and large specific surface area. The catalytic CoN x sites are simultaneously created during the formation of N–MPC. The use of glucose-urea resin as the carbon and nitrogen sources significantly increases the nitrogen content as high as 8.8 at% in the MPC. The synthesized Co/N–MPC demonstrates superb catalytic activity toward oxygen reduction reaction. The direct borohydride fuel cell using the Co/N–MPC shows a power density as high as 170 mW cm −2 which is much higher than the cell using 10 wt.% Pt/C but slightly lower than the cell using 20 wt.% Pt/C as the cathode catalyst at ambient conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Micro-TiO2 bowls are prepared by spray-dried precursors from Ti(OR)4 sols. [•] Carbon coating effects on capacity vary significantly with TiO2 morphology. [•] Carbon coating improves performances of bowls with a thick wall. [•] Cycling between 0 and 3V activates carbon layer on carbon-coated TiO2. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the composites of LiBH4 and AlF3 were prepared and their hydrogen storage properties were investigated. The AlF3 addition to LiBH4 resulted in significant decreases in dehydrogenation temperature. All the xLiBH4 +AlF3 (x =1, 2, 3, 5) composites started to release hydrogen from about 100°C. The dehydrogenation of the composites was accomplished through several steps, depending on the molar ratio of LiBH4 to AlF3. A new phase Li3AlF6 was formed during the first dehydrogenation step, which further reacted with LiBH4. AlB2 was formed only at temperatures higher than 300°C. Li2B12H12 was detected as an intermediate. The dehydrogenation reactions have significantly reduced and thus favorable enthalpy changes. However, the reversibility of the composites needs to be improved. [Copyright &y& Elsevier]

Abstract: A series of polypyrrole (PPY)-modified carbon-supported Co(OH)2 catalysts [Co(OH)2-PPY-C] with different types of carbon supports and the PPY and Co(OH)2 contents are synthesized to investigate the effect of the Coic>x and h name="dbnd" />Nh name="dbnd" /> sites on the oxygen reduction reaction (ORR). X-ray photoemission spectroscopy results reveal that the Coic>x and h name="dbnd" />Nh name="dbnd" /> sites dominate the four- and two-electron transfer ORR, respectively. The carbon support and the PPY and Co(OH)2 contents of the catalysts determine the distribution of the Coic>x and h name="dbnd" />Nh name="dbnd" /> sites. The competition between these two sites determines the overall electron number of the ORR. A direct borohydride fuel cell using an optimal Co(OH)2-PPY-C as the cathode catalyst exhibits a maximum power density of 550mWcm−2 at 80°C. [Copyright &y& Elsevier]

Abstract: An amorphous Fe-based catalyst supported on polypyrrole-modified carbon nanotubes is synthesized by a chemical method. The microstructure, surface composition and morphology are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The synthesized amorphous Fe-based catalyst is composed of amorphous FeOOH and microcrystalline Fe2O3. Compared with a crystalline FeOOH catalyst, the amorphous Fe-based catalyst demonstrates higher electrocatalytic activity toward the oxygen reduction reaction (ORR), due to its amorphous structure and large specific surface area. It is considered that amorphization of transition metal compounds could be one of the methods used to improve their catalytic activity toward the ORR. [ABSTRACT FROM AUTHOR]

Abstract: The electrooxidation behavior of dimethyl ether (DME) dissolved in acidic, neutral or alkaline anolyte has been studied. The cyclic voltammetry measurements reveal that DME in alkaline anolyte demonstrates higher electrooxidation reactivity than that in acidic or neutral anolyte. With increasing the NaOH concentration in the anolyte, the electrooxidation reactivity of DME can be further improved. Direct dimethyl ether fuel cells (DDFCs) are assembled by using Nafion membrane as the electrolyte, Pt/C as the cathode catalyst, and Pt–Ru/C as the anode catalyst. It is found that the use of alkaline anolyte can significantly improve the performance of DDFCs. A maximum power density of 60mWcm−2 has been achieved when operating the DDFC at 80°C under ambient pressure. [Copyright &y& Elsevier]

Abstract: A direct hydrazine fuel cell using H2O2 as the oxidizer has been developed. The N2H4/H2O2 fuel cell is assembled by using Ni–Pt/C composite catalyst as the anode catalyst, Au/C as the cathode catalyst, and Nafion membrane as the electrolyte. Both anolyte and catholyte show significant influences on cell voltage and cell performance. The open-circuit voltage of the N2H4/H2O2 fuel cell reaches up to 1.75V when using alkaline N2H4 solution as the anolyte and acidic H2O2 solution as the catholyte. A maximum power density of 1.02Wcm−2 has been achieved at operation temperature of 80°C. The number of electrons exchanged in the H2O2 reduction reaction on Au/C catalyst is 2. [Copyright &y& Elsevier]

Abstract: A polypyrrole modified carbon-supported cobalt hydroxide (Co(OH)2-PPY-C) has been prepared by the impregnation-chemical method and used as the electrode catalyst in a direct borohydride fuel cell (DBFC). The microstructure of Co(OH)2-PPY-C has been characterized by X-ray diffraction and transmission electron microscopy. The cell performance and short-term performance stability of the DBFC using the Co(OH)2-PPY-C as catalysts have been investigated. A maximum power density of 83mWcm−2 has been achieved at 0.6V under ambient conditions. The Co(OH)2-PPY-C catalyst demonstrates a smaller value of polarization than the carbon-supported Co(OH)2 catalyst. Results from electrochemical impedance spectrum analysis confirm that the polypyrrole addition to the cathode effectively decreases its resistance. During operation of the DBFC using Co(OH)2-PPY-C as catalyst, the Co(OH)2 tends to be converted into CoHO2. [Copyright &y& Elsevier]