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Cobalt manganese hydroxides with well-defined nanowire morphology (CoMn-HW) is scalable fabricated by adjusting solution contents, Mn/Co ratio and alkaline species. To further improve the conductivity of CoMn-HW, GO is introduced during fabrication process and reduced to rGO according to the high temperature and alkali atmosphere. By optimizing the adding mass of rGO, CoMn-HW/rGO with sandwiched like structure is successfully synthesized for supercapacitor electrode. The composite delivers a high specific capacitance of 784 F g−1 at current density of 0.5 A g−1, good rate capability (84.2% capacitance retention after current density increase 10 times). Moreover, an asymmetric supercapacitor with CoMn-HW/rGO10 as the positive electrode and active carbon as the negative electrode, is assembled and delivers a maximum energy density of 38.3 Wh kg−1 and power density of 8000 W kg−1, representing its potential in energy storage and conversion systems. • Co, Mn-hydroxides with nanowire morphology is scalable fabricated. • CoMn-HW/rGO with sandwiched like structure is synthesized under optimal synthesis condition. • An asymmetric supercapacitor based on CoMn-HW/rGO and AC is assembled with high energy and power densities. [ABSTRACT FROM AUTHOR]

In this article, ZnCo 2 O 4 nanowires deposited with two kinds of typical layered double hydroxides (Ni–Al,Co–Al LDH) are developed via scalable method. Two materials all display core–shell hierarchical structure. High specific capacitance of 2041 F g−1 and 1586 F g−1 are obtained for ZnCo 2 O 4 @Co–Al LDH and ZnCo 2 O 4 @Ni–Al LDH,respectively. Combining with active surface and synergistic effect, the role of hierarchical structure in enhancing performance is revealed. Moreover, two all solid state supercapacitors based on fabricated materials as positive electrodes, activated carbon as negative electrodes and PVA–KOH as polymer electrolyte are assembled. The maximum power and energy densities of ZnCo 2 O 4 @Co–Al LDH//AC are 6200 W kg−1 and 50.1 Wh kg−1, respectively. While the power and energy densities of ZnCo 2 O 4 @Ni–Al LDH//AC are 3400 W kg−1 and 27.8 Wh kg−1. At last, an energy storage–conversion system, based on solar cell as input device and assembled asymmetric supercapacitor ZnCo 2 O 4 @Co–Al LDH//AC as output device, is integrated as a self–sustaining power device, indicating its potential in practical applications. In this article, ZnCo 2 O 4 nanowires deposited with two kinds of typical layered double hydroxides (LDHs) are developed via scalable method. Combining with active surface and synergistic effect, the role of hierarchical structure of each material in enhancing performance is revealed. Moreover, an energy storage–conversion system, based on solar cell as input device and assembled asymmetric supercapacitor as output device, is integrated as a self–sustaining power device, further indicating its potential in practical applications. Image 1 [ABSTRACT FROM AUTHOR]

A novel three-dimensional (3D) porous nickel-cobalt (Ni-Co) film on nickel foam is successfully prepared and further used as an efficient anode for direct urea-hydrogen peroxide fuel cell (DUHPFC). By varying the cobalt/nickel mole ratios into 0%, 20%, 50%, 80% and 100%, the optimized Ni-Co/Ni foam anode with a ratio of 80% is obtained in terms of the best cell performance among five anodes. Effects of the KOH and urea concentrations, the flow rate and operation temperature on the fuel cell performance are investigated. Results show DUHPFC with the 3D Ni-Co/Ni foam anode exhibits a higher performance than those reported direct urea fuel cells. The cell gives an open circuit voltage of 0.83 V and a peak power density as high as 17.4 and 31.5 mW cm −2 at 20 °C and 70 °C, respectively, when operating on 7.0 mol L −1 KOH and 0.5 mol L −1 urea as the fuel at a flow rate of 15 mL min −1 . Besides, when the human urine is directly fed as the fuel, direct urine-hydrogen peroxide fuel cell reaches a maximum power density of 7.5 mW cm −2 with an open circuit voltage of 0.80 V at 20 °C, showing a good application prospect in wastewater treatment. [ABSTRACT FROM AUTHOR]

In this paper, the graphene oxide nanosheets are simultaneously reduced and deposited on nickel foam (denoted as Ni-foam@GNS) by one step electrodeposition method. The interconnected crumpled graphene nanosheets grown on Ni foam serve as a three-dimensional (3D) conductive skeleton for hydrothermal deposition of MnO 2 nanosheets by in-situ redox reaction. The MnO 2 nanosheets anchored on the graphene covered nickel foam (denoted as Ni-foam@GNS@MnO 2 ) show unique 3D porous interconnected networks. The samples are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), N 2 adsorption–desorption measurements and fourier transform infrared spectroscopy (FT-IR). The capacitive performances are researched by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The results reveal that the Ni-foam@GNS@MnO 2 electrode exhibits a high specific capacitance of 462 F g −1 at 0.5 A g −1 and excellent capacitance retention of 93.1% after 5000 cycles at 10 A g −1 . Furthermore, the Ni-foam@GNS@MnO 2 electrode delivers a high energy density of 26.1 Wh kg −1 even at a high power density of 3981 W kg −1 . These results demonstrate that the Ni-foam@GNS@MnO 2 composite offers great promise in large-scale energy storage device applications. [ABSTRACT FROM AUTHOR]

A novel and binder free Co@graphite/paper electrode is prepared by electrodeposition Co nano-sheet on the surface of a graphite layer modified paper substrate. The morphology and phase structure of the Co@graphite/paper electrode are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer, transmission electron microscope and X-ray diffractometer. The catalytic activity of the Co@graphite/paper electrode for H 2 O 2 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The catalyst combines tightly with the paper and exhibits a good stability. The oxidation current density reaches to 580 mA cm −2 in 2 mol dm −3 NaOH and 0.5 mol dm −3 H 2 O 2 at 0.5 V. Besides, we illustrate the reaction mechanization of the H 2 O 2 electrooxidation on the Co film. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen peroxide (H2O2) replaced oxygen (O2) as oxidant has been widely investigated due to its faster reduction kinetics, easier storage and handling than gaseous oxygen. The main challenge of using H2O2 as oxidant is the chemical decomposition. In this article, by using different C2H5OH/H2O volume ratio as the solvent, Co3O4 with different morphologies (nanosheet, nanowire, ultrafine nanowire net, nanobelts, and honeycomb-like) direct growth on Ni foam are synthesized via a simple solvothermal method for the first time. Results show that the introduction of ethanol could obviously improve the catalytic performance toward H2O2 electroreduction. The sample prepared in the solution with the C2H5OH/H2O volume ratio of 1:2 shows the best catalytic performance among the five samples and a current density of 0.214 A cm−2 is observed in 3.0 mol L−1 KOH + 0.5 mol L−1 H2O2 at −0.4 V (vs. Ag/AgCl KCl), which is much larger than that on the other metal oxides reported previously, almost comparable with the precious metals. This electrode of Co3O4 directly grown on Ni foam has superior mass transport property, which combining with its low-cost and facile preparation, make it a promising electrode for fuel cell using H2O2 as the oxidant. [Copyright &y& Elsevier]

Highlights: [•] β-Ni(OH)2 was modified via a template-free method by using different nickel salt. [•] The effects on the morphology and electrochemical behaviors were investigated. [•] The β-Ni(OH)2–SO4 2−/Ni-foam electrode displays 1025.3Fg−1 at 1.0Ag−1. [ABSTRACT FROM AUTHOR]

Highlights: [•] Al-substituted β-Ni(OH)2 were prepared by a simple template-free growth method. [•] The effect of Al contents on the electrochemical performances was investigated. [•] The specific discharge capacity was greatly enhanced by the addition of Al. [Copyright &y& Elsevier]

Abstract: A novel three-dimensional electrode consisting of Pd doped porous Ni film supported on Ni foam (Pd-porous Ni/Ni) is successfully prepared. The porous Ni film is synthesized by electrodeposition of Ni nanoparticles using hydrogen bubbles as a dynamic template. Pd doping is carried out via a chemical replacement reaction between Ni film and Na2PdCl4 solution. The obtained electrode exhibits a three-dimensional (3D) porous structure allowing the full utilization of catalyst surface active sites. The morphology of the electrode and the distribution of Pd on Ni particle surfaces are characterized by scanning electron microscope and energy dispersive X-ray spectrometer. The structure is analyzed using an X-ray diffractometer. The catalytic performance of the porous 3D electrode is evaluated by voltammetry and chronoamperometry. Results show that the electrode displays high catalytic activity and good stability for NaBH4 electrooxidation. The oxidation current density of NaBH4 on the Pd-porous Ni/Ni in 3.0 mol L−1 NaOH containing 0.1 mol L−1 NaBH4 at −0.6 V reaches 2.2 A mg−1, which is about 22 times of that on Pd/C (0.1 A mg−1) reported previously. [Copyright &y& Elsevier]

[Display omitted] • OMC@NiO/Ni is synthesized via solvothermal reaction and subsequent calcination treatment. • "Trunk-leaf vein" structure endows OMC@NiO/Ni with superior electrochemical performance. • An asymmetric supercapacitor based on OMC@NiO/Ni and rGO/VO x as positive and negative electrodes respectively, is assembled. Supercapacitors are sustainable energy storage devices with the characteristics of high power density, long life span and ultrafast charge-discharge time. Herein, considering low conductivity of NiO and inspired by the "trunk-leaf vein" structure, mesoporous carbon and nickel dots are introduced into structure reacting as electron scaffold via facile hydrothermal and annealing procedures. Special hierarchical structure is obtained with oxygen modified mesoporous carbon (OMC) as core and NiO sheets as core accompanying with metallic nickel dots deposited on NiO sheets. Such "trunk-leaf vein" architecture can effectively ensure more active sites contacting with electrolyte, furthermore provide conductive scaffolds for electron transport. As expected, the OMC@NiO/Ni exhibits high specific capacitance of 651.3 F g−1 at 2 A g−1 and superior cycling life of 92.2% after 4000 cycles. Moreover, a novel negative electrode rGO/VO x is synthesized ascribe to the superior capacitance and life span. At last, an asymmetric device is assembled using OMC@NiO/Ni as positive electrode and rGO/VO x as negative electrode, which delivers maximum energy density of 44.3 Wh kg−1, high power density of 12,000 W kg−1 and excellent cycling life of 94.5% after 5000 cycles. The high performance of OMC@NiO/Ni renders it a potential material for energy storage-conversion equipments. [ABSTRACT FROM AUTHOR]

Abstract: The growth of CuO nanosheet arrays on Cu foil was demonstrated. The morphology and structure of the CuO were examined by scanning electron microscopy and X-ray diffraction spectroscopy. The catalytic performance of the obtained CuO/Cu electrode for hydrogen peroxide electroreduction in 3.0moldm−3 KOH was evaluated by means of cyclic voltammetry and chronoamperometry. The CuO/Cu electrode shows an onset potential for H2O2 electroreduction comparable to Co3O4 nanowire arrays grown on Ni foam and around 100mV more negative than precious metal catalysts, such as Pt and Pd, demonstrating its good catalytic activity for H2O2 electroreduction. The stabilized mass current density for H2O2 electroreduction on the CuO/Cu electrode at −0.3V reached about 57% of that on Co3O4 nanowire arrays grown on nickel foam. Compared to conventional fuel cell electrodes fabricated by mixing active materials with conducting agents and polymer binders, this electrode of CuO nanosheet arrays directly grown on Cu has superior mass transport property, which combining with its low-cost and facile preparation, make it a promising electrode for fuel cell using H2O2 as the oxidant. [Copyright &y& Elsevier]

Abstract: We report a new method of preparation of a methanol-tolerant Se/Ru cathode catalyst for the direct methanol fuel cell (DMFC) , whereby selenium is deposited on ruthenium nanoparticles by H2-reduction of SeO2 in aqueous solution at room temperature. The obtained Se/Ru(aq) was studied by electrochemical measurements and tested as a cathode catalyst in H2–air and direct methanol fuel cells. The new catalyst formulation (Se/Ru(aq)) is shown to be superior to Se/Ru synthesized from xylenes solvent and to Ru black by RRDE measurements, in terms of both activity and selectivity for complete oxygen reduction to water. Although Ru black is less active, the Tafel slopes and activation energies of Se/Ru catalysts and reduced-Ru black are similar, implying similar ORR mechanisms. In H2–air fuel cell tests, Se/Ru(aq) was more active than Se/Ru(xyl) at all voltages. Compared to Ru black, Se/Ru(aq) was superior at low current densities, but Ru black slightly exceeded the performance of Se/Ru at high current densities. To explain the RRDE and fuel cell observations, the two roles of Se as an inhibitor of Ru oxidation and as a site-blocker are discussed. [Copyright &y& Elsevier]

Abstract: Spherical clusters of Ni(OH)2 nanosheets are directly grown on skeletons of nickel foam via a facile template-free spontaneous growth method. The obtained electrode (β-Ni(OH)2/Ni-foam) is characterized by X-ray diffractometry, scanning and transmission electron microscopy and thermal analysis. Results show that Ni(OH)2 has a β-phase structure and presents on the nickel foam skeleton mostly as spherical clusters with a diameter of ∼10μm. The spheres are composed of nanosheets with thickness of ∼60nm, width of ∼230nm and length up to ∼2μm, and the nanosheets are assembled by nanoparticles with diameter of ∼20nm. The electrochemical performance of the β-Ni(OH)2/Ni-foam electrode is evaluated by cyclic voltammetry and galvanostatic charge–discharge tests. The difference between the oxygen evolution reaction onset potential and the anodic peak potential for this electrode (∼100mV) is larger than that for β-Ni(OH)2 nanosheets and nanotubes powder electrode (∼65–77mV) and much larger than that for commercial spherical β-Ni(OH)2 powder electrode (∼25–47mV), indicating that the β-Ni(OH)2/Ni-foam electrode can be fully charged. The specific discharge capacity of β-Ni(OH)2 in the β-Ni(OH)2/Ni-foam electrode reaches 275mAhg−1, which is close to the theoretical value, lower than that of β-Ni(OH)2 nanotubes (315mAhg−1), but higher than that of nanosheets (219.5mAhg−1), commercial micrometer grade spherical powders (265mAhg−1) and microtubes (232.4mAhg−1). [Copyright &y& Elsevier]

Abstract: The open circuit potentials (OCPs) of H2O2 at Pt, Pd, Au, and glassy carbon electrodes are measured in H2SO4 and NaOH electrolyte solutions. Effects of concentration of H+, OH− and H2O2 as well as temperature on the OCP of H2O2 are investigated. The OCP of H2O2 is much lower than its theoretical reduction potential in both acidic and basic medium. The OCP is actually a mixed potential of H2O2 electroreduction and electrooxidation simultaneously occurring at electrode surfaces and it is more close to the equilibrium potential of H2O2 electrooxidation rather than electroreduction. The OCP of H2O2 is around 0.77–0.80V at [H+]=[H2O2]=1.0moldm−3 in H2SO4 solution and is about 0–0.06V at [OH−]=[H2O2]=1.0moldm−3 in NaOH at 298K on Pt, Pd, Au and GC electrodes. The OCP of H2O2 is independent of H2O2 concentration within the range of 0.01 to 1.0moldm−3. It increases approximately linearly with the logarithm of H+ concentration from 0.02 to 2.0moldm−3, decreases with the logarithm of OH− concentration from 0.01 to 1.0moldm−3 and decreases with increase of temperature from 278K to 333K. The linear equations were presented and discussed. [Copyright &y& Elsevier]

Abstract: Nanowire arrays of mixed oxides of Co and Ni freely standing on Ni foam are prepared by a template-free growth method. The effects of Ni content on the morphology, structure and catalyst performance for oxygen evolution reaction are investigated by scanning electron microscopy, X-ray diffraction spectroscopy and electrochemical techniques including cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. A transformation from nanowire arrays to nanoplate arrays is found with the increase of the atomic ratio of Ni to Co in the preparation solution. The NixCo3−xO4 electrode obtained at 1:1 of Ni:Co in the preparation solution exhibits nanowire array structure and has better catalytic performance for oxygen evolution reaction than other NixCo3−xO4 and Co3O4 electrodes. The catalytic activities of the NixCo3−xO4 and Co3O4 electrodes are correlated with their surface roughness. Superior stability of the NixCo3−xO4 nanowire array electrode is demonstrated by a chronopotentiometric test. The reaction orders with respect to OH− on the NixCo3−xO4 electrode are close to 2 and 1 at low and high overpotentials, respectively. [Copyright &y& Elsevier]

Abstract: Direct carbon fuel cells are promising power sources using solid carbon directly as fuel. Their performances significantly depend on the electrooxidation activity of carbon fuel. Electrooxidation of activated carbon particulates in molten Li2CO3–K2CO3 was investigated by potentiodynamic and potentiostatic method. Results indicated that the electrooxidation performance of activated carbon was significantly enhanced by pre-soaking with Li2CO3–K2CO3 and by treatment with HF, HNO3 and NaOH, respectively. The onset potential negatively shifted by around 100 mV and the current density increased by around 50 mA cm−2 after pre-soaking. The non-oxidant acids (HF) treatments are more effective than oxidant acid (HNO3) and base (NaOH) treatments. HF treated activated carbon exhibited the highest activity among all the samples. The enhancement in electrooxidation performance can be closely correlated with the increase in surface area and porosity caused by acid and base treatments. [Copyright &y& Elsevier]

Abstract: Au/Ni-foam electrodes with three dimensional network structures are prepared by simple spontaneous deposition of nano-sized Au particles onto nickel foam surface in an aqueous solution of AuCl3. Their morphology and catalytic performance for NaBH4 electrooxidation and H2O2 electroreduction in NaOH solution are investigated. Au particles with diameters smaller than 100nm are uniformly deposited on the whole surface of all skeletons of the nickel foam substrate. The onset potential for NaBH4 electrooxidation and H2O2 electroreduction is about −1.2V and −0.1V, respectively. A direct liquid feed alkaline NaBH4–H2O2 fuel cell is constructed using Au/Ni-foam electrode as both the anode and the cathode. The effects of the concentration of NaBH4 and H2O2 and operation temperature on the fuel cell performance are investigated. The fuel cell exhibits an open circuit voltage of about 1.07V and a peak power density of 75mWcm−2 at a current density of 150mAcm−2 and a cell voltage of 0.5V operating on 0.2moldm−3 NaBH4 and 0.5moldm−3 H2O2 at 40°C. [Copyright &y& Elsevier]

Abstract: A high performance alkaline direct borohydride–hydrogen peroxide fuel cell with Pt–Ru catalyzed nickel foam as anode and Pd–Ir catalyzed nickel foam as cathode is reported. The electrodes were prepared by electrodeposition of the catalyst components on nickel foam. Their morphology and composition were analyzed by SEM–EDX. The effects of concentrations of NaBH4 and H2O2 as well as operation temperature on the cell performance were investigated. The cell exhibited an open circuit voltage of about 1.0V and a peak power density of 198mWcm−2 at a current density of 397mAcm−2 and a cell voltage of 0.5V using 0.2moldm−3 NaBH4 as fuel and 0.4moldm−3 H2O2 as oxidant operating at room temperature. Electrooxidation of NaBH4 on Pt–Ru nanoparticles was studied using a rotating disk electrode and complete 8e− oxidation was observed in 2moldm−3 NaOH solution containing 0.01moldm−3 NaBH4. [Copyright &y& Elsevier]

Abstract: Pd nanoparticles were immobilized on Au disk electrode and kinetics of hydrogen peroxide electroreduction on the Pd electrode in 0.1M H2SO4 solution was investigated using a rotating disk electrode method. The phase and particle size of palladium were characterized by XRD measurements. The morphology of Pd on Au was examined using SEM. We found that the hydrogen peroxide reduction on Pd nanoparticles proceeds via a two-electron process. The reaction order is one with respect to hydrogen peroxide. An apparent activation energy of 55kJmol−1 was calculated from exchange currents at different temperature. The lower activation energy and higher exchange current density demonstrated that hydrogen peroxide reduction has a faster kinetics than oxygen reduction. Electrolyte anions significantly affect hydrogen peroxide reduction activity, and the activity decreases in the order > >Cl−, which is consistent with the increasing adsorption bond strength of the anions. [Copyright &y& Elsevier]

Abstract: Mg–Li–Al–Ce–Zn and Mg–Li–Al–Ce–Zn–Mn alloys were prepared using a vacuum induction melting method. Their electrochemical oxidation behavior in 0.7M NaCl solution was investigated by means of potentiodynamic polarization, potentiostatic oxidation, electrochemical impedance technique and scanning electron microscopy examination. Their utilization efficiencies and performances as anode of metal–hydrogen peroxide semi-fuel cell were determined. The Mg–Li–Al–Ce–Zn–Mn exhibited higher discharge activity and utilization efficiency than Mg–Li–Al–Ce–Zn, and gave improved fuel cell performance. The utilization efficiency of Mg–Li–Al–Ce–Zn–Mn is comparable with that of the state-of-the-art magnesium alloy anode AP65. The magnesium–hydrogen peroxide semi-fuel cell with Mg–Li–Al–Ce–Zn–Mn anode presented a maximum power density of 91mWcm−2 at room temperature. Scanning electron microscopy and electrochemical impedance studies indicated that the alloying element Mn prevented the formation of dense oxide film on the alloy surface and facilitated peeling off of the oxidation products. [Copyright &y& Elsevier]

Abstract: Spinel structure Co3O4 nanoparticles with an average diameter of around 17nm were prepared and evaluated as electrocatalysts for H2O2 reduction. Results revealed that Co3O4 exhibits considerable activity and good stability for electrocatalytic reduction of H2O2 in 3M NaOH solution. The reduction occurs mainly via the direct pathway when H2O2 concentration is lower than 0.5M. An Al-H2O2 semi fuel cell using Co3O4 as cathode catalyst was constructed and tested at room temperature. The fuel cell displayed an open circuit voltage of 1.45V and a peak power density of 190mWcm−2 at a current density of 255mAcm−2 operating with a catholyte containing 1.5M H2O2. This study demonstrated that Co3O4 nanoparticles are promising cathode catalysts, in place of precious metals, for fuel cells using H2O2 as oxidant. [Copyright &y& Elsevier]

Abstract: Mg–Li, Mg–Li–Al and Mg–Li–Al–Ce alloys were prepared and their electrochemical behavior in 0.7M NaCl solutions was investigated by means of potentiodynamic polarization, potentiostatic current–time and electrochemical impedance spectroscopy measurements as well as by scanning electron microscopy examination. The effect of gallium oxide as an electrolyte additive on the potentiostatic discharge performance of these magnesium alloys was studied. The discharge activities and utilization efficiencies of these alloys increase in the order: Mg–LiMg–Li–Al>Mg–Li–Al–Ce. Mg–Li–Al–Ce exhibited the best performance in term of activity, utilization efficiency and activation time. [Copyright &y& Elsevier]

Abstract: The direct carbon fuel cell is a special type of high temperature fuel cell that directly uses solid carbon as anode and fuel. As an electrical power generator for power plants, it has a higher achievable efficiency (80%) than the molten carbonate and solid oxide fuel cells, and has less emissions than conventional coal-burning power plants. More importantly, its solid carbon-rich fuels (e.g. coal, biomass, organic garbage) are readily available and abundant. In this review, some fundamental study results of electrochemical oxidation of carbon in molten salts are summarized. Recent developments in direct carbon fuel cell configurations and performance are also discussed. [Copyright &y& Elsevier]

A series of prototype direct methanol fuel cells (DMFCs) were constructed and operated under identical procedures and conditions except for the surface compositions of the anode electrocatalysts. The cathode electrocatalyst was Pt black (loading 2 mg/cm2, specific surface area: ca. 27 m2/g), the electrolyte membrane was Nafion™ 117, and the anode electrocatalysts were a series of Pt–Ru adatom (Pt–Ruad) nanoparticles (loading 2 mg/cm2, specific surface area: ca. 27 m2/g) prepared by a direct surface reductive deposition of Ruad onto Pt black. The optimum surface coverage of Pt by Ruad was ca. 33% for DMFCs operating at 60 °C. The optimum ranged from ca. 30 to 60% at 90 °C. A DMFC using Pt–Ruad nanoparticles supported on carbon (Vulcan XC-72™) as anode electrocatalyst was operated for 20 days at 8 h each day without loss of activity. These results, combined with those from an in situ cyclic voltammetry study, indicate that no significant Ruad dissolution and/or redistribution occurred during fabrication and operation of the prototype DMFCs. [Copyright &y& Elsevier]

The surface of Pt nanoparticles was cleaned and saturated with hydrogen by treatment first with a 3% aqueous solution of H2O2 and then with hydrogen gas under water at room temperature. Reaction between the surface hydrogen and aqueous RuCl3 deposited 0.18 surface equivalents of Ruad onto the Pt nanoparticles. The deposition was repeated several times, with each reaction depositing ∼0.18 surface equivalents more Ruad onto the Pt–Ruad nanoparticles. The resulting Pt–Ruad nanoparticles were analysed using cyclic voltammetry, CO stripping voltammetry, and as catalysts for electrooxidation of MeOH in three-electrode experiments and in prototype direct methanol fuel cells. The optimum surface coverage (θRu) for electrooxidation of MeOH was ∼0.33 under these conditions. [Copyright &y& Elsevier]

We report the performance of a polymer electrolyte membrane direct 2-propanol fuel cell (DPFC). The cell consisted of a Pt-Ru (atomic ratio of 1:1) black anode, a Pt black cathode, and a Nafion®-117 membrane electrolyte. The cell was operated at 90 °C with aqueous 2-propanol as fuel and with oxygen as oxidant. The performance of the cell operating on 2-propanol is substantially higher than when it was operating on methanol at current densities lower than ∼200 mA/cm2. The electrical efficiency of the direct 2-propanol fuel cell is nearly 1.5 times that of the direct methanol fuel cell at power densities below 128 mW/cm2. Studies on the effects of electrocatalyst loading, of 2-propanol concentration, and of oxygen pressure on cell performance indicate that the cells operating on 2-propanol require lower anode and cathode loadings than cells operating on methanol. Cathode poisoning by 2-propanol is less severe than by methanol. Hydrogen gas evolution observed at the anode at low current densities indicated that catalytic dehydrogenation of 2-propanol occurred over the anode catalyst. A rapid voltage drop occurred at high current densities and after operating the cell for extended periods of time at constant current. The rapid voltage drop is an anode phenomenon. [Copyright &y& Elsevier]

The organometallic precursor Ru4(μ-H)4(CO)12 (1) reacts with dihydrogen (60 atm, room temperature hexane as solvents, 3 h) over either blacked Pt gauze or Pt black powder to deposit Ru adatoms (Ruad) and CO on the Pt surface. The deposition is self-poisoned by adsorbed CO, stopping when a specific coverage of Pt by CO is reached. The results from the electrooxidation of the adsorbed CO, from base voltammograms recorded in aqueous sulfuric acid, from exhaustive anodic stripping of Ruad, and from the potentiodynamic and potentiostatic electrooxidation of MeOH, all show that the deposition self-poisons after ca. 0.05 surface equivalents (moles Ruad vs. moles Pt surface) of Ruad are deposited on blacked Pt gauze. The deposition over Pt black powder self-poisons after depositing ca. 0.10 surface equivalents of Ruad. A direct CH3OH fuel cell using the resulting black Pt–Ruad powder was constructed by hot-pressing the catalyst into a Nafion® membrane. Contrary to expectations, the Pt–Ruad catalyst did not lose significant amounts of surface Ru during either hot pressing the membrane electrode assembly, nor during operation of the fuel cell at 90 °C. [Copyright &y& Elsevier]

In this study, Acacia catechu (AC) extract was used as a stabilizing and reducing agent to synthesize silver (Ag) and titanium dioxide (TiO 2) nanoparticles (NPs). By using AC extract, the synthesis process becomes more environmental friendly, economical, and advantageous. The morphology and size of synthesized Ag and TiO 2 NPs were determined by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Dynamic light scattering (DLS), Atomic force microscopy (AFM), and Scanning electron microscopy (SEM). Elemental composition was determined by using Fourier transform infrared spectroscopy (FTIR) and Energy dispersive X-ray spectrometer (EDX), EDS mapping and X-ray photoelectron spectroscopy (XPS). The observations from TEM, SEM, AFM, and DLS revealed that synthesized products are spherical, hexagonal, polydispersed, and ranged within 6–20 nm size. XRD result demonstrated well crystallized and smaller size NPs are formed in both cases. FTIR and XPS analysis depicted the presence of flavonoids, terpenoids, and amino groups in addition to benzene ring agents; which act as stabilizing agents as well as possible aromatic primary amine groups may also be attached with the surface of Ag and TiO 2 NPs. Furthermore, the synthesized AgNPs exhibited strong antibacterial activity against S-aureus and catalytic application over Rose Bengal, Rhodamine B, and 4 nitrophenol dyes as compared to TiO 2 under sunlight (solar irradiation). Overall, Ag and TiO 2 NPs exhibit high potential in the development of antibacterial materials for both Gram-positive as well as Gram-negative bacteria and catalytic material for photocatalytic degradation of a certain type of hazardous dyes or chemicals, thereby paving the way for the treatment and bioremediations. The reason could be high energy and smaller size particles were active in the photo-catalysis and antibacterial performance of AgNPs compared to TiO 2 NPs. Unlabelled Image • Ag and TiO 2 nanoparticles (NPs) were synthesized by green synthesis method using extract of Acacia catechu. • XRD, XPS spectra analysis and DLS revealed the confirmation of the Ag and TiO 2 NPs. • SEM and TEM revealed spherical and poly-dispersed particles. • ZETA potential revealed that well stabilized Ag and TiO 2 NPs. • Ag and TiO 2 NPs successfully degraded carcinogenic chemicals and have antibacterial potential against S-Aureus. [ABSTRACT FROM AUTHOR]

The need for safe, cost-effective aqueous magnesium ion batteries has led to high electrochemical performance designs of materials and structures to meet strict requirements. A composite of manganese dioxide and carbon molecular sieves (δ -MnO 2 @CMS) with a core-shell structure is used as the cathode in the aqueous magnesium ion battery, which not only solves the inherent deficiencies of low conductivity from manganese dioxide but also maximizes its specific capacities via a hierarchical structure. In addition, the anode material, nanowire VO 2 (formed via a solvothermal reaction) is rarely investigated in this system. Interestingly, this material can form new electrodes with more stable structures after the first charged process and avoids the formation of MgO, thereby providing insertion/extraction of magnesium ions into/from the host anode material. An aqueous rechargeable magnesium ion battery can be successfully assembled using the two electrodes designed above. This device shows high rate properties and delivers reversible capacities of 112.2, 94.6, 78.7, 69.5, and 59.1 mAh g−1 at current densities of 50, 100, 200, 300, and 500 mA g−1. Image 1 • δ -MnO 2 @CMS with core-shell structure is synthesized by hydrothermal method. • The nanowire VO 2 as anode is obtained by simple one-step hydrothermal process. • The Mg2+ insertion/deinsertion mechanism of two electrodes is explored. • Assembled aqueous magnesium-ion battery exhibits excellent rate property. [ABSTRACT FROM AUTHOR]

The borohydride oxidation reaction (BOR) is the main reaction in the anode of direct borohydride fuel cells (DBFCs), which is also fundamental to highlight the advantages of DBFCs. However, the catalysis of BOR still faces many challenges. On the one hand, further breakthroughs in catalytic activity are sought to achieve high performance of the anode; on the other hand, the negative effects brought by the side reactions, including the bubble effect, loss of fuel utilization, poisoning of the catalyst, etc., are urgently needed to be mitigated. Essentially, the running of the anode is the catalysis of BOR, so the catalytic viewpoint is critical to solving the above problem. In this work, an updated review of the effects of electrode design and the modulation of the catalytic environment on the anode is provided. Specifically, the electrode design is reviewed mainly from the perspective of catalytic activity, selectivity, and protective strategies. Besides, the modulation of the catalytic environment is emphasized in the systematic configuration and reactant transfer engineering. This work is expected to provide an in-depth understanding of the catalysis of BOR and afford significant inspiration toward the design of the anode. In this work, an updated review of the effects of electrode design and the modulation of the catalytic environment on the anode of direct borohydride fuel cells is provided. [Display omitted] • Based on a catalytic perspective DBFC anodes were reviewed. • Engineering strategies for electrode design are summarized. • The effects of catalytic environmental on the anode are discussed. • Challenges and outlooks for the design of DBFC anodes are provided. [ABSTRACT FROM AUTHOR]

The adoption of effective, minimal, and versatile electrocatalysts for water splitting to generate hydrogen fuels is of critical importance. The bulk of newly described materials have considerable onset potential, but their electrocatalytic activity is limited by weak electrical conductivity and a limited range of catalytic sites. The combination of a few precious metals added with transition metal-based compounds is a novel and captivating approach. Herein, cobalt ferrite oxide (Co 2 FeO 4) @ palladium oxide (PdO) nanostructures have been prepared through the combined use of hydrothermal and ultraviolet (UV) irradiation techniques. For hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics, the modified composition offers a high concentration of active sites, improved electrical conductivity, and stability. The Co, Fe, and Pd ions at the composite system's interface may affect the adsorption energy of reaction intermediates synergistically, enabling the process to continue with less potential. The electrocatalyst Co 2 FeO 4 @PdO demonstrates an excellent bifunctional approach to electrochemical water splitting (EWS) for HER and OER in alkaline medium. As-prepared electrocatalyst shows an overpotential value of 269 and 259 mV for HER and OER at 10 and 20 mA/cm2 current densities respectively. The low charge transfer resistance values such as 72.2 and 62.4 Ω and durability for 48 h has been observed toward HER and OER , support this material as an efficient and durable electrocatalyst for energy conversion systems. [Display omitted] • Effective Cobalt–Iron-Ferrite oxides and Palladium-oxide based bifunctional electrocatalyst. • Promising activity for HER and OER with lower Tafel slope values in the alkaline media. • Longer stability and durability for 20 h. [ABSTRACT FROM AUTHOR]

A binder-free and flexible Au electrode is prepared by spontaneous deposition of Au onto a A4 (A4-paper)-8B (8B pencil)-Ni Film substrate (ABNi) which is assembled by electrodeposition of nanoscale Ni particles on the surface of A4 paper coated by 8B pencil. The morphology and phase structure of the (A4-paper)-8B (8B pencil)-Ni Film-Au (ABNiAu) electrode are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffractometer. The catalytic activity of the ABNiAu electrode for NaBH 4 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The electrode exhibits a high electric conductivity and the activity substance attaches to the surface of paper substrate tightly and does not fall off at all and the nanoscale Ni and Ni Au alloy enhance the broken of the B H bond in the BH 4 − , all of which lead to a high catalytic activity for NaBH 4 electrooxidation. The oxidation current density reaches 300 mA cm −2 in 1 mol dm −3 NaOH and 0.1 mol dm −3 NaBH 4 at −0.2 V. The exchanged electrons (n) is 6.0 (8.0 in theory), which indicates that the ABNiAu electrode has much higher utilization efficiency of the fuel than our reported LaNi 5 /Pd (n = 4) electrode. [ABSTRACT FROM AUTHOR]

[Display omitted] • LiCoO 2 powder leaching was achieved by microwave via deep eutectic solvent. • Two kinds of deep eutectic solvents were used in this microwave-ultra-fast leaching. • Over 90 % of Li and Co were leached at 4 min and 160 W by adding urea / lactic acid. • Li and Co leaching were controlled by shrinking core model of chemical reaction. The large-scale use of electric vehicles produced massive discarded lithium-ion batteries, containing many recyclable valuable metals and toxic and harmful substances. Biodegradable and recyclable deep eutectic solvent (DES) is considered a green recycling technology for spent LIBs. Herein, we proposed a microwave-enhanced approach to shorten the leaching time in the urea/lactic acid: choline chloride: ethylene glycol DES system. The dipole moments induced by urea or lactic acid on LiCoO 2 surface increased over two orders of magnitude under the high electric field. Because of this, over 90 % of Li and Co can be fast leached at 4 min and 160 W in the urea/lactic acid: choline chloride: ethylene glycol DES system. Meanwhile, we established two models to explain the leaching mechanism of metal ions from their leaching kinetics and micro-level behavior, and named them dot-etching and layer-peeling processes, respectively. By further analyzing, we found that the dot-etching can be attributed to the synergistic effect of reduction and coordination, which caused the surface of leaching residues porous. The layer-peeling process depends on neutralization, and the leaching residues had a smooth surface in this process. This work highlights the effect of microwave-enhanced strategy and DES surface chemistry on spent electrode materials recovery. [ABSTRACT FROM AUTHOR]

A novel electrode of PdCu nanoparticles modified free-standing reduced graphene oxide (rGO) framework (PdCu@rGOF) is fabricated via electrodeposition and chemical reduction and employed to the direct sodium borohydride-hydrogen peroxide fuel cell (DBHPFC). The resultant catalyst reveals excellent catalytic performance towards hydrogen peroxide (H 2 O 2) electroreduction reaction (HPRR) and sodium borohydride (NaBH 4) electrooxidation reaction (BOR) along with low activation energy (E a). Numerically, the PdCu@rGOF electrode delivers an HPRR current density of 455.2 mA cm−2 at 0 V (2 mol L−1 H 2 SO 4 +1.3 mol L−1 H 2 O 2). Additionally, the current density of BOR reaches up to 1065.3 mA cm−2 at 0 V for 2 mol L−1 NaOH and 0.3 mol L−1 NaBH 4. Meanwhile, the mechanism studies show that HPRR and BOR catalyzed by PdCu@rGOF mainly relates 2-electron-transfer process and quasi-8-electron-transfer process, respectively. Subsequently, PdCu@rGOF is assembled into a fuel cell, yielding the optimal power density of 188.9 mW cm−2. The open circuit potential (OCP) of DBHPFC is about 1.70 V at 293.15 K. The superior electrochemical performance of the optimized electrode can be attributed to the distinctive architecture and the strong adsorption and bond-breaking ability of Pd nanoparticles. This work indicates that the as-prepared PdCu@rGOF can be a promising catalyst for DBHPFC. [Display omitted] • A novel 3D through-hole rGOF framework has been successfully prepared. • PdCu@rGOF displays an excellent catalytic performance for HPRR and BOR. • PdCu@rGOF can be applied to both anode and cathode of DBHPFC. • DBHPFC presents high power density and operation stability. [ABSTRACT FROM AUTHOR]

Development of efficient, low cost and multifunctional electrocatalysts for water splitting to harvest hydrogen fuels is a challenging task, but the combination of carbon materials with transition metal-based compounds is providing a unique and attractive strategy. Herein, composite systems based on cobalt ferrite oxide-reduced graphene oxide (Co 2 FeO 4) @(rGO) using simultaneous hydrothermal and chemical reduction methods have been prepared. The proposed study eliminates one step associated with the conversion of GO into rGO as it uses direct GO during the synthesis of cobalt ferrite oxide, consequently rGO based hybrid system is achieved in-situ significantly, the optimized Co 2 FeO 4 @rGO composite has revealed an outstanding multifunctional applications related to both oxygen evolution reaction (OER) and hydrogen counterpart (HER). Various metal oxidation states and oxygen vacancies at the surface of Co 2 FeO 4 @rGO composites guided the multifunctional surface properties. The optimized Co 2 FeO 4 @rGO composite presents excellent multifunctional properties with onset potential of 0.60 V for ORR, an overpotential of 240 mV at a 20 mAcm−2 for OER and 320 mV at a 10 mAcm−2 for HER respectively. Results revealed that these multifunctional properties of the optimized Co 2 FeO 4 @ rGO composite are associated with high electrical conductivity, high density of active sites, crystal defects, oxygen vacancies, and favorable electronic structure arisinng from the substitution of Fe for Co atoms in binary spinel oxide phase. These surface features synergistically uplifted the electrocatalytic properties of Co 2 FeO 4 @rGO composites. The multifunctional properties of the Co 2 FeO 4 @ rGO composite could be of high interest for its use in a wide range of applications in sustainable and renewable energy fields. Illustration of multifunctional surface properties of Co 2 FeO 4 @rGO composite. [Display omitted] • In situ rGO and cobalt ferrite oxide (Co 2 FeO 4 @rGO) composite is prepared. • The synthesized composite exhibited tri-functional water catalysis. • Composite shows an overpotential of 240 mV at a 20 mAcm−2 for OER. • A long term durability of 48 h was also demonstrated by composite material. [ABSTRACT FROM AUTHOR]

Abstract: Ni(OH)2 nanosheets are directly grown on nickel foam by a simple template-free growth process. Their microstructure and surface morphology are studied by X-ray diffraction spectroscopy and scanning electron microscopy. The XRD and SEM results show that Ni(OH)2 has a β-phase structure and covers the nickel foam skeleton with nanosheets. This β-Ni(OH)2/Ni-foam electrode exhibits a high specific electric quantity of 790.3 C g−1 approaching the theoretical value (1040.6 C g−1) and high electrochemical activity. Asymmetric supercapacitor has been fabricated successfully using β-Ni(OH)2/Ni-foam nanosheets as positive electrode and activated carbon as negative electrode in a KOH aqueous electrolyte. The electrochemical capacitances of this supercapacitor are investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. An asymmetric supercapacitor AC/6 mol L−1 KOH/β-Ni(OH)2/Ni-foam could be cycled reversibly in the high-voltage region of 0–1.6 V and displays intriguing performances with a specific capacitance of 105.8 F g−1 and high energy density of 36.2 W h kg−1. Importantly, this asymmetric supercapacitor device exhibits an excellent long cycle life along with 92% specific capacitance retained after 1000 cycles. [Copyright &y& Elsevier]

• The CeS 2 incorporation modulates the internal electronic state. • Ce species stabilizes some of the surface sulphide against self-oxidation during OER process. • The strategy of iron dopant is conducive to induce plentiful S-defects. • The nanoparticles-rich structure affords ample holes and irregular flow channels. • Polyvalent Ce species provides great redox property, enhancing the electrocatalytic activity. Design and fabrication of high-efficiency nickel-rich electrocatalytic materials for sluggish oxygen evolution reaction (OER) remains a tremendous challenge. Modulating internal electronic state and accelerating charge transfer are two of vital means to optimizing electrocatalysts. In this work, nanoparticles-rich Fe-(CeS 2 /Ni 3 S 2) hybrid material with abundant heterointerfaces and sulfur-defects are facilely synthesized. The strategy of iron dopant is conducive to induce more sulfur defects. The cerium species can modulate the internal electronic state and stabilize some of the surface sulphide against self-oxidation during OER process. This self-supported heterogeneous material requires overpotentials of 254 and 372 mV to reach the current densities of 100 and 500 mA cm−2 in alkaline condition. The addition of urea or ethanol to the bath solution has been demonstrated as an efficient strategy for reducing the onset potential and decreasing energy consumption, thereby confirming the feasibility of applying this approach to energy-saving hydrogen production through electrolysis wastewater splitting. [ABSTRACT FROM AUTHOR]

[Display omitted] • The composite was synthesized by a hydrothermal and vapor phase sulfidation method. • The hetrostruction and MXene improve the Na+ reaction kinetics. • The composite exhibits excellent rate and superior cycle stability. Molybdenum trioxide (MoO 3) is regarded as a promising material for rechargeable batteries attributed to its low cost, high theoretical capacity and eco-friendliness. Herein, N-doped carbon (NC) coated MoO 3 /MoS 2 composite decorated on MXene nanosheets (MoO 3 /MoS 2 /NC/MXene) has been synthesized by gas-phase vulcanization and coating of NC. The electrical conductivity and kinetics of ion diffusion/transport are greatly enhanced due to the vulcanization, NC coating and introduction of MXene. As a consequence, the composite exhibits high discharge capacity of 464 mAh/g at a current density of 0.1 A/g and still maintains a capacity of 202 mAh/g at a high current density of 5 A/g when used as the anode material for sodium-ion batteries. Furthermore, the electrode material still remains a high discharge capacity of 320 mAh/g with the capacity retention rate of nearly 100 % after 2000 cycles at a current density of 1 A/g. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defective graphene with high density of defects is prepared via Flash Joule Heating. • An ultrahigh reversible capacity of 2450 mAh g−1 is achieved for defective graphene. • Nascent defects, lithium plating and 3D structure contribute to the high capacity. • Excess lithium storage and fading mechanisms are revealed. • Insights for designing high-capacity electrodes based on defect engineering. Introducing defects is an effective approach to promote the lithium ion storage ability of host material. Constructing pure defects is beneficial to understand the lithium ion storage mechanism in the defects. Herein, we fabricate defective graphene without intricate functional groups via a flash Joule heating (FJH) technique within a mere 1 ms. The FJH-reduced graphene lattice harbors a multitude of defects, and its unique three-dimensional structural network enables an ultra-high lithium ion storage capacity. Moreover, the highest capacity of F-RGO-5 reaches 2500 mAh/g in the 800th cycle, its three-dimensional architecture allows it to withstand high currents and prolonged cycles without drastic failures. Nascent defects and defect-induced lithium plating predominantly contribute to capacity enhancement during cycling, while dendrite formation primarily leads to decay. Our findings present an approach to defect-based designs of high-capacity lithium anodes and provide valuable insights into their energy storage mechanisms. [ABSTRACT FROM AUTHOR]

The electrochemical nitrate reduction reaction (eNO 3 RR) to ammonia (NH 3) is a promising alternative method to the Haber-Bosch process that requires high temperature and pressure. In this contribution, the integrated Co 3 O 4 nanowire arrays on Ni foam (Co 3 O 4 /NF) are reported to exhibit the outstanding performance with a high NH 3 yield rate of 117.01 mg h−1cm−2, a superior NH 3 Faradaic efficiency of 99.28 %, a high effective current density of 1475.71 mA cm−2, and a good operation durability during 40 consecutive recycling tests (40 h) in 1.0 M NaOH (0.1 M NaNO 3). The high-valence metal cations as electron-deficient centers can act as Lewis-acid sites, favorably interacting with the Lewis base NO 3 −, and accordingly boosting the NO 3 − adsorption and activation. Moreover, the in-situ growth array configuration provides the substantial active sites and constructs a fast electron-transport channel, thus facilitating the conversion of NO 3 −-to-NH 3. Density functional theory (DFT) calculations also reveal that the Co atoms as the active sites are preferred to adsorb NO 3 −, implying that the NO 3 − electroreduction dominates the cathodic reaction rather than hydrogen evolution reaction. This study provides a viable method to design integrated electrodes with enhanced eNO 3 RR activity and selectivity, which might have broad prospects in the application of renewable energy. The efficient nitrate-to-ammonium conversion is achieved by the integrated Co 3 O 4 nanowire arrays rich in electron-deficient centers. Benefitted from the massive exposed active sites, improved conductivity and charge transfer efficiency, as well as the abundant Lewis acid sites, Co 3 O 4 nanowire arrays present the brilliant nitrate electroreduction performance, including 117.01 mg h−1 cm−2 NH 3 yield rate and 99.28 % Faradaic efficiency in 1.0 M NaOH with 0.1 M NO 3 −. [Display omitted] • High-valence metal cations are favorable to boost NO 3 − adsorption and activation. • Integrated nanowire arrays configuration can provide massive exposed active sites. • Co 3 O 4 /NF can provide a fast electron-transport channel and excellent conductivity. • Co 3 O 4 /NF presents the considerable activity and stability towards eNO 3 RR process. [ABSTRACT FROM AUTHOR]

Abstract: The electrode of array of CuO nanosheet is prepared via a template-free growth method, and it is doped by Ag via the silver mirror reaction. The morphology of Ag-doped CuO nanosheet is examined by scanning electron microscopy. The phase structure of the Ag-doped CuO nanosheet is analyzed by X-ray diffraction spectroscopy. The supercapacitance behavior of Ag-doped CuO nanosheet is investigated by cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy. The results show that the thickness of a single nanosheet is up to around 150nm. The specific capacitance of the Ag-doped CuO nanosheet electrode is 689Fg−1 at 1Ag−1 and 299Fg−1 at 10Ag−1, respectively, much higher than that of the unmodified CuO nanosheet arrays (418Fg−1 at 1Ag−1 and 127Fg−1 at 10Ag−1). The improved capacitance is explained in terms of the presence of dispersed Ag particle coated the CuO nanosheet arrays having good electrical conductivity. [Copyright &y& Elsevier]

Abstract: The synthesis, electrochemical analysis, and hydrogen-air fuel cell testing results for a new type of Se/Ru catalyst called Se/Ru(aq) were described in Part 1. In this second report, we present methanol tolerance studies and direct methanol fuel cell testing for the same catalyst. A “methanol-tolerant” catalyst does not oxidize methanol, nor becomes depolarized by its presence, which is a desirable property for DMFC cathodes used with methanol-permeable membranes or in mixed-reactant designs. In perchloric acid electrolyte, the Se/Ru(aq) catalyst was found to be highly tolerant to 1.0M methanol. More importantly, in fuel-cell testing as a DMFC cathode, Se/Ru(aq) was shown to be highly tolerant to methanol crossing through the membrane (from the anode side) up to a feed concentration of 17M. The results were compared to those obtained using unmodified Ru black and Pt black at the DMFC cathode, in order to gain insight into the catalyst function and to compare the performance to relevant benchmarks. Compared to Pt cathodes, the performance of Se/Ru(aq) is significantly better at high methanol concentrations (e.g., 17M), suggesting their use either in DMFCs with high methanol feed concentrations or in mixed-reactant fuel cells. [Copyright &y& Elsevier]

Abstract: The electrochemical performances of magnesium, magnesium–lithium–aluminum–cerium and magnesium–lithium–aluminum–cerium–yttrium as the anode of magnesium–hydrogen peroxide semi-fuel cells have been studied by methods of potentiodynamic, potentiostatic and electrochemical impedence measurements. The surface morphologies of magnesium and its alloys have been examined by scanning electron microscopy (SEM). It has been found that magnesium–lithium–aluminum–cerium and magnesium–lithium–aluminum–cerium–yttrium electrodes are less corrosion resistant than that of magnesium electrode in 0.7molL−1 NaCl solution and the corrosion current density decreases with the following order: magnesium

Abstract: Acetone is the main product of 2-propanol electrooxidation in both acid and alkaline electrolytes; it always co-exists with 2-propanol in the reaction solution due to its liquid nature. Whether acetone will affect the electrooxidation of 2-propanol has not been well documented, which is a key issue that needs to be addressed for the direct 2-propanol fuel cell. In this study, the influence of acetone on the electrooxidation of 2-propanol in alkaline medium is investigated, using state-of-the-art Pd electrode, by cyclic voltammetry and chronoamperometry. The electrode is prepared using a chemical replacement method, by dipping nickel foam into acidified PdCl2 solution, and characterized by scanning electron microscopy. We found that the presence of acetone adversely affects electrooxidation performance of 2-propanol and substantially reduces the oxidation current of 2-propanol on Pd in alkaline medium. The acetone poisoning effect is interpreted by a competitive adsorption mechanism, in which acetone adsorbs onto Pd surface and occupies the active sites for 2-propanol electrooxidation, leading to a significant decrease in the number of these sites for 2-propanol electrooxidation. The results of this study point out that efficient electrocatalysts for 2-propanol electrooxidation in alkaline electrolytes must be non-adsorptive to acetone besides being highly active to 2-propanol oxidation. [ABSTRACT FROM AUTHOR]

Abstract: Co3O4 nanowire arrays freely standing on nickel foam are prepared via template-free growth followed by thermal treatment at 300°C in air. Their morphology is examined by scanning and transmission electron microscopy. The electrochemical capacitance behavior of the self-supported binderless nanowire array electrode is investigated by cyclic voltammetry, galvanostatic charge–discharge test and electrochemical impedance spectroscopy. The results show that nanowires are formed by nanoplatelets packed roughly layer by layer. They densely cover the nickel foam substrate and have diameters around 250nm and the lengths up to around 15μm. The Co3O4 nanowires display a specific capacitance of 746Fg−1 at a current density of 5mAcm−2. The capacitance loss is less than 15% after 500 charge–discharge cycles. The columbic efficiency is higher than 93%. [Copyright &y& Elsevier]

Electricity production and modeling of microbial fuel cell (MFC) from continuous beer brewery wastewater was studied in this paper. A single air-cathode MFC was constructed, carbon fiber was used as anode and diluted brewery wastewater (COD=626.58mg/L) as substrate. The MFC displayed an open-circuit voltage of 0.578V and a maximum power density of 9.52W/m3 (264mW/m2). Using the model based on polarization curve, various voltage losses were quantified. At current density of 1.79A/m2, reaction kinetic loss and mass transport loss both achieved to 0.248V; while ohmic loss was 0.046V. Results demonstrated that it was feasible and stable for producing bioelectricity from brewery wastewater; while the most important factors which influenced the performance of the MFC are reaction kinetic loss and mass transport loss. [Copyright &y& Elsevier]

Potassium ion batteries or capacitors are a promising technology for large-scale energy storage due to the abundant resource and low cost of potassium. However, the development of stable electrode materials with high capacity, capable rate ability, and excellent cycling stability remains a challenge. Herein, carbon dots modified reduced graphene oxides (LAP-rGO-CDs) are designed and synthesized via a rapid and green microwave-assisted method with l -Ascorbic acid 6-palmitate (LAP) as the reducing agent. LAP-rGO-CDs present enlarged interlayer spacing and faster ion transfer rate owing to the introducing of carbon dots. Serving as a potassium ion battery electrode, LAP-rGO-CDs showed a high specific capacity of 299 mAh g−1 at 1 A g−1 and excellent cycling stability. Moreover, a LAP-rGO-CDs//AC full carbon-based potassium ion capacitor is assembled and displays a maximum energy density of 119 Wh kg−1 and a power density of 5352 W kg−1. This work demonstrates the potential application of LAP-rGO-CDs for high-performance potassium ion storage. [Display omitted] [ABSTRACT FROM AUTHOR]

Integrating transition metal complexes with carbon-based materials, especially graphene, is a useful strategy for synthesizing effective hydrogen evolution catalysts. Herein, we report a design of hollow hexagonal NiSe–Ni 3 Se 2 nanosheets grown on reduced graphene oxide (NiSe–Ni 3 Se 2 /rGO) by a simple hydrothermal method as an effective catalyst for hydrogen evolution reaction (HER) in the full pH range. In 0.5 M H 2 SO 4 , the NiSe–Ni 3 Se 2 /rGO possesses 112 mV to achieve 10 mA cm−2 and a small Tafel slope (61 mV dec−1). In 1.0 M PBS and 1.0 M KOH, the overpotentials are 261 and 188 mV at 10 mA cm−2, and Tafel slopes are 103 and 92 mV dec−1, respectively. Meanwhile, it owns good cycle stability and durability over 20 h in the whole pH range (0-14). In all solutions, the HER performance of NiSe–Ni 3 Se 2 /rGO is better than that of NiSe–Ni 3 Se 2. This is because the rGO substrate accelerates the electron transfer and improves the electrical conductivity, increasing HER activity of catalyst. • The hollow hexagonal NiSe-Ni3Se2 nanosheets uniformly decorate the rGO. • The hollow structure exposes more active sites and transport pathways. • The hybrid material exhibits superior performance for HER in all pH media. • The stability of the composite is good under a variety of pH conditions. [ABSTRACT FROM AUTHOR]

The highly porous electrode of a crisscrossed CoNi nanosheets array grown on reduced graphene oxide decorated Ni foam (CoNi/rGO@Ni foam) is fabricated through a facile dip and dry method followed by electroreduction and electrodeposition methods. The phase composition and morphology of the electrode are characterized by XRD, SEM, TEM, and EDS. In single electrode tests, CoNi/rGO@Ni foam electrode displays an excellent catalytic performance (330 mA cm−2 at 0.6 V) and stability towards urea electrooxidation when comparing to Ni foam and CoNi nanosheets modified Ni foam (CoNi@Ni foam) electrode. Besides, a low initial oxidation potential of urea electro-oxidation to 0.14 V is achieved on the CoNi/rGO@Ni foam electrode. The introducing of rGO to the electrode greatly reduced the reaction activation energy from 14.47 to 10.35 kJ mol−1. Besides, large active surface area (261.67 cm2) is also obtained from the electrode. The CoNi/rGO@Ni foam anode exhibits a maximum power density of 12.58 mW cm−2 in direct urea-hydrogen peroxide fuel cell tests. Excellent performance shows in single electrode tests and fuel cell tests suggest that addition of rGO to the electrode is an easy and feasible method to enhance the performance of the catalyst. • Highly porous electrode: crisscrossed nanosheets array grows on rGO modified Ni foam. • The influence of rGO on the catalytic performance of the electrode was researched. • Low initial oxidation potential towards urea electro-oxidation was obtained. • Achieved an excellent performance and stability when practical use in DUHPFC. [ABSTRACT FROM AUTHOR]

Seeking the efficient and robust electrocatalysts necessarily enhances performance of hydrogen evolution reaction (HER). Increasing the surface active sites is a means to improve the performance. Herein, we use the Ni 0·85 Se anchored on reduction of graphene oxide (Ni 0·85 Se/rGO) hybrid material skillfully established by one-step facile hydrothermal method as a robust and stable electrocatalyst applying to hydrogen evolution reaction (HER). In terms of morphology, Ni 0·85 Se nanospheres composed of many nanosheets are uniformly distributed on the graphene sheet layer. We also detailedly analyze its properties. Based on the interaction between Ni 0·85 Se and rGO, and the roles of graphene are as a substrate to heighten conductivity, possesses more active surface area by limiting growth of Ni 0·85 Se, and increases dispersion for exposing more active surface area and enlarge ion/electron transfer rate. In HER, the Ni 0·85 Se/rGO catalyst displays the overpotential of 128 mV with a common current density of 10 mA cm−2, a small Tafel slope of 91 mV dec−1, an extremely low onset potential of 37 mV, outstanding stability that a high current retention of 97.7% after 1000 cycles and well long-term stability for 18 h, outperforming the capability of Ni 0·85 Se nanospheres in alkaline solution for HER. The above results indicate that the Ni 0·85 Se/rGO hybrid material is a good HER ability and non-noble metal electrocatalyst has potential value in HER. • The Ni 0.85 Se nanospheres uniformly decorate the rGO sheets. • The Ni 0.85 Se/rGO electrocatalyst possesses more active surface area. • The stability of the composites can reach 97.7%. • The hybrid material exhibits superior performance for HER. [ABSTRACT FROM AUTHOR]