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Journal Cover Electrocatalysis
  [SJR: 0.817]   [H-I: 17]   [2 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1868-2529 - ISSN (Online) 1868-5994
   Published by Springer-Verlag Homepage  [2351 journals]
  • Electrochemical Sensor Using Molecular Imprinting Polymerization Modified
           Electrodes to Detect Methyl Parathion in Environmental Media
    • Authors: Fa-Ru Wang; Gang-Juan Lee; Neelamegan Haridharan; Jerry J. Wu
      Pages: 1 - 9
      Abstract: In this research, the electrochemical sensor was fabricated based on glassy carbon electrode decorated by the reduced gold nanoparticles and molecularly imprinted polymer (MIP) on the electrode surface with methyl parathion (MP) as the template molecule. Four parameters, such as amount of gold nanoparticles, deposition time of gold nanoparticles, pH of acetate buffer solution, and extraction time of ethanol acidic solution, have been successfully determined by achieving the optimal sensor preparation. The MP in aqueous matrix can be quantitatively determined in the range of 0.05 to 15 μM with two linear equations at low and high ranges. In addition, the selectivity of the sensor as prepared toward the MP measurement is superior by comparing with similar structured compounds, such as imidacloprid and fenitrothion. This study also demonstrates that the deviation of current response from the MP in different matrix samples is negligible using MIP/Au/glassy carbon electrode sensor with recoveries ranged from 87.7 to 124.8%. ᅟ Graphical
      PubDate: 2018-01-01
      DOI: 10.1007/s12678-017-0411-9
      Issue No: Vol. 9, No. 1 (2018)
  • Oxygen Reduction on Rh(111) and Se-Modified Rh(111) Surfaces
    • Authors: Shahid Iqbal; Helmut Baltruschat
      Pages: 40 - 46
      Abstract: Oxygen reduction is studied at Rh(111) and Rh(111) modified by a Se adlayer. Controlled mass transport was achieved in a flow through cell. Hydrogen peroxide, detected at a second electrode behind the working electrode, amounted to few percent at Rh(111) and for low Se coverages, at higher coverages it amounted up to 40%. Small coverages of Se lead to a decrease of the over potential by 50 mV. The Tafel slope amounts to 80 mV at potentials positive of the hydroxyl reduction peak and nearly 200 mV at potentials below. These values do not change after modification by Se. Hydrogen adsorption is completely suppressed for Se coverages of 0.5 (Se atoms per Rh atoms). In addition, the point of total zero charge was determined to be 0.2 V using the CO charge displacement method. Graphical ᅟ
      PubDate: 2018-01-01
      DOI: 10.1007/s12678-017-0407-5
      Issue No: Vol. 9, No. 1 (2018)
  • Performance of Pd Cathode Catalyst Electrodeposited on Gas Diffusion Layer
           in Polymer Electrolyte Membrane Fuel Cells
    • Authors: Sujin Gok; Youngkwang Kim; Taeho Lim; Hyun-Jong Kim; Oh Joong Kwon
      Pages: 59 - 66
      Abstract: Performance of a polymer electrolyte membrane fuel cell with a Pd cathode catalyst was systemically investigated in this study. The Pd catalyst was directly formed on a gas diffusion layer by using electrodeposition (Pd/GDL). The electrodeposition formed aggregates of Pd nanoparticles on a gas diffusion layer with the preferred orientation of Pd(111) and Pd(200). In addition, the Pd aggregates mainly formed on the top surface of the gas diffusion layer. The membrane electrode assembly was fabricated with Pd/GDL as the cathode. The performance of the membrane electrode assembly was investigated by varying hot pressing parameters and back pressures, and the operating condition for the polymer electrolyte membrane fuel cell was optimized. Notably, introducing back pressure increased operating current density at 0.6 V by up to 45%. Durability of the membrane electrode assembly was also examined. Negligible deterioration of surface morphology of the Pd catalyst was observed even after accelerated stress testing, except for a slight increase in particle size. The results indicate that deterioration of the Pd cathode catalyst was not a major factor affecting overall single-cell performance degradation. Graphical Current-potential curve obtained at the back pressure of 250 kPag and the FE-SEM image of Pd electrochemically deposited on the cathode side of the MEA
      PubDate: 2018-01-01
      DOI: 10.1007/s12678-017-0420-8
      Issue No: Vol. 9, No. 1 (2018)
  • Relationship Between the Redox Reactions on a Bipolar Plate and Reverse
           Current After Alkaline Water Electrolysis
    • Authors: Yosuke Uchino; Takayuki Kobayashi; Shinji Hasegawa; Ikuo Nagashima; Yoshio Sunada; Akiyoshi Manabe; Yoshinori Nishiki; Shigenori Mitsushima
      Pages: 67 - 74
      Abstract: In order to efficiently operate the alkaline water electrolyzers with renewable energy, behaviors of the electrolyzer during start-up or shut-down must be unveiled, because they might be suffered by reverse current that naturally flows. The mechanism of the reverse current in alkaline water electrolyzer having relation between the electrolyzer operating conditions and cell voltage has been investigated using a bipolar-type electrolyzer which consists of two cells. The electrodes were nickel mesh, which are conventional electrodes for alkaline water electrolyzer. The amount of natural reverse current measured during off-load was proportional to the current loaded until just before stopping the operation. The increase in the charge would result from the increasing oxide on the anode of the bipolar plate. Cell voltages were above 1.4 V at all cases just when the electrolyzer is forcibly opened the circuit to stop. The major redox couple of the reverse current would be [NiO2/NiOOH] and [H2/H2O] due to the cell voltage and the redox couples. The open circuit cell voltage of the cathode terminal side cell gradually decreased to 0.3 V, while that of the anode terminal side cell was maintained above 1.1 V. Therefore, nickel oxides on the anode of the bipolar plate would be reduced, and the cathodic active material of hydrogen and nickel for the cathode side of the bipolar plate would be oxidized during the reverse current flows. Ultimately, the reverse current would stop when the redox state of both sides of the bipolar plate had the same oxidation state. Graphical
      PubDate: 2018-01-01
      DOI: 10.1007/s12678-017-0423-5
      Issue No: Vol. 9, No. 1 (2018)
  • Correction to: Relationship Between the Redox Reactions on a Bipolar Plate
           and Reverse Current After Alkaline Water Electrolysis
    • Authors: Yosuke Uchino; Takayuki Kobayashi; Shinji Hasegawa; Ikuo Nagashima; Yoshio Sunada; Akiyoshi Manabe; Yoshinori Nishiki; Shigenori Mitsushima
      Pages: 75 - 75
      Abstract: The vertical axis of Fig. 6 has been corrected.
      PubDate: 2018-01-01
      DOI: 10.1007/s12678-017-0447-x
      Issue No: Vol. 9, No. 1 (2018)
  • Unfolding the Hidden Reactions in Galvanic Cells
    • Authors: Tomer Noyhouzer; Daphnée Bellemare-Alford; Nicholas A. Payne; Eric Martineau; Janine Mauzeroll
      Abstract: The relationship between the potential of the cell reaction (Ecell), the entropy change (ΔS), and the enthalpy change (ΔH) is well established. Yet, there is surprisingly a very narrow range of experimental aqueous galvanic cells that follow thermodynamic predictions. The redox and equilibrium reactions used within Pourbaix diagrams are presented a priori to establish the limitations and application range of thermodynamic relationships within complex electrochemical systems, the Zn-Cu (Daniell cell) and Pb-Cu cells. These are then tested to validate the theoretical discussion. Specifically, the electromotive force of both cells is measured as a function of the temperature in order to calculate the thermodynamic properties of the reaction: concomitantly to the voltage measurements, the temperature, the pH, and the surface state of the electrodes. Graphical
      PubDate: 2018-02-26
      DOI: 10.1007/s12678-018-0459-1
  • Design of Pd-Pb Catalysts for Glycerol and Ethylene Glycol
           Electrooxidation in Alkaline Medium
    • Authors: Tristan Asset; Alexey Serov; Monica Padilla; Aaron J. Roy; Ivana Matanovic; Marian Chatenet; Frederic Maillard; Plamen Atanassov
      Abstract: Unsupported PdxPb1-x electrocatalysts were synthesized by a modified sacrificial support method (SSM) and thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Their electrochemical activity was evaluated for the electrooxidation reactions of ethylene glycol (EGOR) and glycerol (GOR) in alkaline electrolytes, reaching an onset of − 510 mV vs. the normal hydrogen electrode (NHE) for the EGOR and the GOR vs. − 430 mV vs. NHE for the EGOR and the GOR on the Pd-black. Additional mechanistic insights were provided by DFT calculations, showing that the presence of Pb resulted in a stronger binding of the OHads, therefore explaining the enhanced kinetics for the electrooxidation of C2 (ethylene glycol) and C3 (glycerol) alcohol in this environment. Graphical
      PubDate: 2018-02-26
      DOI: 10.1007/s12678-017-0449-8
  • Electrochemical Observation of High Oxophilicity and its Effect on Oxygen
           Reduction Reaction Activity of Au Clusters Mass-Selectively Deposited on
           Glassy Carbon
    • Authors: Kensaku Kodama; Atsushi Beniya; Noritake Isomura; Yoshihide Watanabe
      Abstract: The measurement procedure of oxophilicity and electrocatalytic activity for oxygen reduction reaction (ORR) on size-selected Au clusters was developed and applied. Mass-selected Au9 clusters were deposited on a glassy carbon substrate under ultrahigh vacuum (UHV) conditions, and the model electrode was transferred to an electrochemical cell with the rotating disk electrode (RDE) configuration. Cyclic voltammetry exhibited a significantly lower oxide-reduction peak potential of the Au clusters than that of bulk Au in the first cycle, thus confirming the exceptionally higher oxophilicities for the former. After performing cyclic voltammetry with an upper limit potential of 1.8 V versus a reversible hydrogen electrode, the ORR activity of the Au clusters was lower than that of bulk Au and bulk Pt. This result was partially ascribed to aggregations of Au clusters during the potential cycles. Graphical ᅟ
      PubDate: 2018-02-19
      DOI: 10.1007/s12678-018-0464-4
  • Ni and Ni x Co y Alloys Electrodeposited on Stainless Steel AISI 316L for
           Hydrogen Evolution Reaction
    • Authors: Melisa J. Gomez; Esteban A. Franceschini; Gabriela I. Lacconi
      Abstract: Ni x Co y electrocatalysts for hydrogen evolution reaction (HER) were synthesized by electrodeposition on AISI 316L stainless steel (denoted as SS316L), as a scalable and economical alternative to be used in alkaline electrolyzers. For this, a previous treatment of the SS316L surface was carried out in order to optimize the deposition of different catalytic films containing Ni and Ni x Co y with different compositions (Ni89Co11, Ni69Co31, and Ni29Co71). The properties of the catalysts were established by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), and the catalytic activity for HER was evaluated by potentiodynamic experiments in 1 M KOH solutions. An increase in the current density toward the hydrogen evolution reaction was found with these Ni x Co y electrodes. For the Ni69Co31 catalyst, current density values 112% higher than those recorded with deposited Ni from conventional Watts bath were obtained. The HER current shows a strong dependence on the content of Co on the alloy that is also evidenced in the electrochemical impedance experiments. The efficiency of electrocatalytic activity for HER was increased after an electrochemical aging treatment, indicating the presence of an activation process, for example with Ni89Co11 electrodes, where higher current density for HER was observed. Graphical ᅟ
      PubDate: 2018-02-17
      DOI: 10.1007/s12678-018-0463-5
  • Hierarchical Ni 3 ZnN Hollow Microspheres as Stable Non-Noble Metal
           Electrocatalysts for Oxygen Reduction Reactions
    • Authors: Bo He; Yao Yuan; Jiacheng Wang; Erum Pervaiz; Xiangting Dong; Zhigang Shao; Minghui Yang
      Abstract: Ternary nitrides are now being considered as one of the emerging advanced functional materials owing to characteristic features and remarkable physicochemical properties that have rationale to substitute precious metals in many applied areas. The present work is focused on Ni3ZnN hollow microspheres for the first time, synthesized by nitridation of the NiO/ZnO precursors in ammonia atmosphere. The precursors composed of 1 μm spheres were made through coordination of terephthalic acid (H2BDC) and Zn2+/Ni2+ cations by solvothermal treatment. The prepared bimetallic nitride is a new single crystalline ternary nitride that belongs to cubic crystal phase (space group Pm-3m, No. 221). Ni3ZnN hollow microspheres were applied as electrocatalyst for proficiently catalyzing the oxygen reduction reactions (ORR), and exhibited very good catalytic activity with the onset potential of 0.81 V versus RHE in alkaline media. After 2000 cycles, Ni3ZnN hollow microspheres show only a 14 mV negative shift in its half-wave potential, suggesting high stability for the ORR. Our current results can show that new ternary nitride is a potential electrocatalytic material for renewable energy resource. Graphical A new ternary metal nitride (Ni3ZnN) has been successfully synthesized through a direct nitridation of the NiO/ZnO hollow microsphere precursors. The prepared bimetallic nitride is a new single crystalline ternary nitride that belongs to cubic crystal phase (space group Pm-3m, No.221). Ni3ZnN were applied as electrocatalyst for proficiently catalyzing the oxygen reduction reaction, and exhibited very good catalytic activity and stability
      PubDate: 2018-02-09
      DOI: 10.1007/s12678-018-0461-7
  • Biomolecule-Free, Selective Detection of o -Diphenol and Its Derivatives
           with a Screen-Printed Electrochemical Sensor
    • Authors: Yu-Ju Chen; Jen-Lin Chang; Natarajan Thiyagarajan; Jyh-Myng Zen
      Abstract: We report here biomolecule-free, selective detection of o-diphenol and its derivatives with a screen-printed electrochemical sensor. It is based on the preparation of a highly stable slurry made of 2,2-diphenyl-1-picrylhydrazyl (DPPH) dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) room temperature ionic liquid for use as screen-printed ink in fabricating the proposed sensor. A detailed investigation by scanning electron microscope (SEM) along with UV-visible and FT-IR spectroscopic studies indicates that DPPH is well dispersed and stabilized by BMIMPF6 ionic liquid. Enhanced current response is observed using the as-printed electrode (designated as SP-DPILE) in electrochemical measurements of o-diphenols with good sensitivity and selectivity. Its selectivity is proved through the discrimination of catechol signal from resorcinol and hydroquinone in the absence of biomolecule auxiliary. This is valuable in real sample analysis, and the feasibility of the SP-DPILE is demonstrated for the detection of gallic acid in green tea by flow injection analysis. A highly stable slurry made of 2,2-diphenyl-1-picrylhydrazyl (DPPH) distributed within room temperature ionic liquid ([BMIM] [PF6]) was developed for use as screen-printing ink in fabricating disposable sensors. Graphical
      PubDate: 2018-02-07
      DOI: 10.1007/s12678-018-0460-8
  • The Effect of Protonated Ethionine Adsorption on Bi(III) Electroreduction
           in Chlorate(VII) Solutions with Varied Water Activity
    • Authors: Agnieszka Nosal-Wiercińska; Mariusz Grochowski
      Abstract: The Bi(III) electroreduction in the presence of the ethionine (Et) was studied under its different protonation and changes of water activity. In order to determine adsorption and kinetic parameters, the following were applied: DC polarography, square wave voltammetry (SWV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The influence of ethionine on the double-layer parameters at the electrode/chlorate (VII) interface and multistep Bi(III) ion electroreduction was found. The multistep Bi(III) electroreduction process is controlled by the kinetics of the formation of active Bi–Et complexes on the electrode surface. The size of the catalytic effect is connected with the equilibrium of the reaction creating active complexes before the successive transition of electrons. Graphical ᅟ
      PubDate: 2018-02-07
      DOI: 10.1007/s12678-018-0456-4
  • Corrosion Behavior of Platinum in Aqueous H 2 SO 4 Solution: Part
           1—Influence of the Potential Scan Rate and the Dissolved Gas
    • Authors: Sadaf Tahmasebi; Mohammad Akhtar Hossain; Gregory Jerkiewicz
      Abstract: Research on the degradation of Pt materials is of high importance to the polymer electrolyte membrane fuel cells (PEMFCs) technology, since their degradation translates into irreversible materials loss and significant deterioration of the PEMFCs’ performance. Polycrystalline platinum (Pt(poly)) serves as a model system in research on Pt-based electrocatalysts for PEMFCs due to its randomly oriented grains separated by grain boundaries, and experimental studies using Pt(poly) create important background knowledge that may be used to identify and understand electrochemical and corrosion phenomena taking place in PEMFCs. In this contribution, we report new results on the corrosion behavior of Pt(poly) in 0.50 M aqueous H2SO4 solution saturated with a neutral (N2(g)) or reactive gas (O2(g) or H2(g)). We analyze the influence of the potential scan rate (s = 0.10, 0.20, 0.50, and 1.00 mV s−1) on the polarization behavior of Pt(poly) in anodic (positive-going) and cathodic (negative-going) directions. A comparative analysis of the impact of dissolved gases on the electrochemical and corrosion behavior of Pt(poly) is performed using cyclic voltammetry and potentiodynamic polarization. Their analysis reveals that the corrosion data obtained at the lowest potential scan rate (s = 0.10 mV s−1) are the most accurate and representative of the corrosion of Pt(poly) in 0.50 M aqueous H2SO4 solution. This is due to the fact that polarization measurements are designed to mimic steady-state conditions, which can only be achieved in the case of s = 0.10 mV s−1 or lower. A comparison of the corrosion data leads to the following observations: (i) Pt(poly) does not undergo corrosion in the electrolyte saturated with H2(g), (ii) it undergoes a slight corrosion in the electrolyte outgassed with N2(g), (iii) it undergoes a substantial corrosion in the electrolyte saturated with O2(g), and (iv) the corrosion rate is more significant in the case of the anodic transient than the cathodic ones (for the same dissolved gas). Graphical abstract The first ever study of Pt(poly) corrosion using potentiodynamic polarization. Anodic and cathodicpotentiodynamic polarization curves for Pt(poly) in 0.50 M aqueous H2SO4 solution saturated with N2(g), O2(g) or H2(g) acquired at a potential scan rate of s = 0.10 mV s-1 and T = 298 K.
      PubDate: 2018-02-01
      DOI: 10.1007/s12678-018-0454-6
  • Facile Synthesis of Ni-Based Catalysts by Adsorption and Conversion of
           Metal Ions on Graphene Oxide for Methanol Oxidation
    • Authors: Xihong Guo; Rongli Cui; Huan Huang; Cheng Li; Huanli Yao; Bing Liu; Lele Zhang; Binggang Xu; Jinquan Dong; Baoyun Sun
      Abstract: Controllable synthesis of highly dispersed non-precious nanocatalysts is an attractive strategy to prepare efficient electrocatalysts for fuel cell applications. In this study, a facile synthesis of Ni-based mono- and bimetallic nanocatalysts has been developed by adsorption and conversion of metal ions on graphene oxide. The morphology and composition of Ni catalyst are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical and electrocatalytic properties of Ni catalysts are studied using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopic techniques. The catalytic performance can be improved easily by increasing the adsorption and deposition cycles of metal ions and changing the composition of precursor metal ions solution. This work will be of general interest to design efficient nanostructured catalysts and find ideal electrocatalysts for application with high catalytic performance and low price. Graphical A facile synthesis of metallic nanocatalysts has been developed by adsorption and conversion of metal ions on graphene oxide
      PubDate: 2018-01-26
      DOI: 10.1007/s12678-018-0457-3
  • Effect of Temperature, Electrode Potential, and Bulk Composition on
           Hydrogen Electrosorption into Palladium-Ruthenium Alloys—Comparative
           Study with Other Binary Systems
    • Authors: Katarzyna Hubkowska; Mariusz Łukaszewski; Andrzej Czerwiński
      Abstract: The influence of temperature between 283 K and 328 K on hydrogen electrosorption into Pd-Ru alloys in the bulk composition range 87–100% at. Pd was studied voltammetrically and chronoamperometrically in 0.5 M H2SO4 solution. The maximum alloy ability to absorb hydrogen decreases with increasing temperature. The extent of hydrogen absorption/desorption hysteresis is slightly reduced with increasing temperature and markedly reduced with increasing Ru bulk content. Both increasing temperature and Ru bulk content results not only in a decrease in the thermodynamic stability of the hydride phase but also in an improvement in the kinetics of hydrogen electrosorption. Pd-Ru alloys containing more than ca. 97% at. Pd absorb more hydrogen than pure Pd, while further Ru additive results in a significant deterioration of the alloy ability to absorb hydrogen. The data on the influence of temperature and alloy bulk composition on the processes of hydrogen electrosorption in Pd binary alloys with Ru, Rh, Pt, and Au have been compared. Graphical ᅟ
      PubDate: 2018-01-23
      DOI: 10.1007/s12678-018-0458-2
  • Silver/Nickel Oxide (Ag/NiO) Nanocomposites Produced Via a Citrate Sol-Gel
           Route as Electrocatalyst for the Oxygen Evolution Reaction (OER) in
           Alkaline Medium
    • Authors: M. Z. Iqbal; R. J. Kriek
      Abstract: A series of Ag/NiO nanocomposite electrocatalysts, with a general molecular formula of Ag x Ni1 − xO, was synthesised employing the citrate sol-gel route and tested for the oxygen evolution reaction (OER) in 0.1 M KOH solution. Crystal structure, morphology and stoichiometry of the catalysts were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The face-centred cubic (fcc) crystalline structure of NiO was revealed as being dominant, having an average crystallite size of 9.6 nm. SEM revealed a non-uniform, cotton-like surface for NiO showing aggregation of particles. Crystallinity of the different synthesised compounds decreased as the Ag content increased. The maximum OER activity was observed for pristine NiO, without any Ag additive, requiring an overpotential of only 263 mV to obtain a current density of 10 mA cm−2 at 25 °C. The addition of Ag inhibited the OER electrocatalytic activity, which might be due to Ag oxidation being observed at 1.431 V. Graphical ᅟ
      PubDate: 2018-01-22
      DOI: 10.1007/s12678-018-0455-5
  • Pt-Ru-NiTiO 3 Nanoparticles Dispersed on Vulcan as High Performance
           Electrocatalysts for the Methanol Oxidation Reaction (MOR)
    • Authors: Velumani Thiagarajan; Palaniswamy Karthikeyan; Ramasamy Manoharan; Srinivasan Sampath; A. Hernández-Ramírez; M.E. Sánchez-Castro; I.L. Alonso-Lemus; F.J. Rodríguez-Varela
      Abstract: We propose a high performance electrocatalyst based on Pt-Ru-NiTiO3 nanoparticles supported on Vulcan carbon (Pt-Ru-NiTiO3/C) for the methanol oxidation reaction (MOR) in acid medium. The electrocatalyst is prepared from a two-step procedure using a wet chemical method. The morphological studies from TEM indicate that Pt-Ru-NiTiO3 nanoparticles are uniformly distributed on Vulcan carbon. The XRD shows the fcc structure of Pt nanomaterials, while the chemical composition examined using XPS indicates the presence of large fractions of Pt0 and Ru0 species (i.e., metallic state), OH− and O2− species are also formed on the surface of the catalyst. The Pt-Ru-NiTiO3/C electrocatalyst exhibits a higher catalytic activity compared to a PtRu/C alloy. Pt-NiTiO3/C is also more active than the alloy. Therefore, on one side, the addition of Ru enhances the MOR through the formation of oxygenated adsorbed species on Ru, which thereby promotes the oxidation of CO to CO2 at more negative potentials (i.e., the bifunctional mechanism). On the other hand, the superior electrocatalytic performance of Pt-Ru-NiTiO3/C is attributed also to the synergistic effects of NiTiO3, which promotes the reaction increasing the current density and shifting the onset potential to even more negative values, suggesting that it also participates in the bifunctional mechanism along with Ru. From the results shown here, Pt-Ru-NiTiO3/C can be a promising anode nanomaterial for direct methanol fuel cells (DMFCs). Graphical ᅟ
      PubDate: 2018-01-15
      DOI: 10.1007/s12678-017-0450-2
  • Functionalized Carbon Nanotubes for Highly Active and Metal-Free
           Electrocatalysts in Hydrogen Evolution Reaction
    • Authors: Tianhao Li; Daomei Tang; Zehua Cui; Bo Cai; Dalin Li; Qianyuan Chen; ChangMing Li
      Abstract: Six kinds of functionalized multiwalled carbon nanotubes (FCNTs) with different functional moieties were utilized as metal-free electrocatalysts towards the hydrogen evolution reaction for the first time. Ethylenediamine-functionalized multiwalled carbon nanotubes (EDA-CNTs) delivered the best HER activity holding a low-onset overpotential of 150 mV, a Tafel slope of 116 mV dec−1, and a Faradaic efficiency (FE) of 94% with a good stability. This HER activity of EDA-CNTs is superior or quite comparable to other reported metal-free HER catalysts, while the preparation of this electrocatalyst is simple, quick, and inexpensive. This good HER performance of EDA-CNTs can be resulted from the high electrical conductivity and its high grafting yield to form more amide groups for enhancement of proton adsorption. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) were successfully used to elucidate the HER process promoted by EDA-CNTs, in which the amide groups were demonstrated to improve the proton adsorption. Graphical
      PubDate: 2018-01-06
      DOI: 10.1007/s12678-017-0452-0
  • Electrochemical Proton Reductions Catalyzed by the Simpler Hexacoordinate
           Iron Compounds as Functional Mimics of the Active Site in [FeFe]
    • Authors: Shang Gao; Qing-Cheng Liang; Qian Duan; Da-Yong Jiang; Jian-Xun Zhao
      Abstract: Ligand-substitution reaction of [(μ-S2C4N2H2)Fe2(CO)6] (1) generated a normal mono-substituted diiron dithiolate derivative [(μ-S2C4N2H2)Fe2(CO)5(PMe3)] (1P) and a simpler hexacoordinate mononuclear compound [(μ-S2C4N2H2)Fe([CO)2(PMe3)2] (2) via distinct reactivity pathways under identical conditions. 1P and 2 could act as the electrochemically functional mimics of the [2Fe] sub-cluster and the distal Fe moiety of the active site of [FeFe] hydrogenase. The electrochemical investigations showed that 2 catalyzed the production of hydrogen from weak acid (acetic acid, HOAc) via two catalytic processes with an initial metal-orbital based reduction. In contrast, the electrocatalytic reaction of 2 with stronger acid (trifluoroacetic acid, TFA) occurred via an initial ligand protonation, and proceeded through different pathways that involved distinct oxidation states of the catalyst. The most striking result obtained in this study was that the hydrogen formation by 2 from TFA occurred at a relatively low overpotential as small as −0.28 V. It could be rationalized by the exclusive employment of iron(II) and iron(I) redox levels in the catalytic cycle, which was consistent with the enzymatic process. The observations might shed light on some aspects of ways by which the model compounds catalyzed the reduction of protons. Graphical
      PubDate: 2018-01-04
      DOI: 10.1007/s12678-017-0453-z
  • Activity and Stability of Pt/C and Pt-Cu/C Electrocatalysts
    • Authors: V. E. Guterman; S. V. Belenov; A. A. Alekseenko; Rui Lin; N. Yu. Tabachkova; O. I. Safronenko
      Abstract: Stability in the course of exploitation and catalytic activity in reactions, taking place on the electrodes, are the most important characteristics of electrocatalysts that determine their application in fuel cells. Relationship of the electrochemical behavior of Pt/C catalysts with their morphology is studied in this article. Negative linear correlation between stability and catalytic activity of Pt/C in the reaction of oxygen electroreduction (ORR) has been established. The procedure for choosing electrocatalysts with the optimal ratio of activity and stability has been proposed. Having used CuxPt/C catalysts as an example, we have shown that bimetallic electrocatalysts, prepared by sequential deposition of copper and platinum, can demonstrate significantly higher activity and stability, compared to Pt/C electrocatalysts. Graphical ᅟ
      PubDate: 2018-01-03
      DOI: 10.1007/s12678-017-0451-1
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