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Journal Cover Electrocatalysis
  [SJR: 0.883]   [H-I: 10]   [0 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  [2280 journals]
  • Spontaneous Deposition of Iridium onto Nickel Substrates for the Oxygen
           Evolution Reaction
    • Abstract: Abstract Spontaneous deposition of Ir onto Ni substrates was investigated as a method to produce electrocatalytic layers for the oxygen evolution reaction in 30 % KOH solution. UV/Vis spectroscopy, cyclic voltammetry and other electrochemical methods are used to investigate the deposition process and the activity of the electrocatalytic coating towards the oxygen evolution reaction. From three solutions (IrCl3+HCl, H2IrCl6+HCl and H2IrCl6), H2IrCl6 is shown to give the most active and stable coating, with deposition times of 45 min at 60∘C enough to increase the activity of the Ni substrate for the oxygen evolution reaction. It is proposed that Ir deposition can occur via the reduction of the Ir precursor coupled to Ni oxidation, as well as the hydrolysis and localised precipitation of the Ir precursor due to the increase in surface pH during Ni dissolution.
      PubDate: 2016-02-05
       
  • Electrochemistry Investigation of the Monolacunary and Their Transition
           Metal Substituent Keggin-Type Polyoxometalates
    • Abstract: Abstract The electrochemical and electrocatalytic behaviors of [XW11O39] n− and [XW11M(H2O)O39] m− (X = B, Si, and P; MII = Mn, Co, and Ni) polyoxometalates were studied with specific emphasis on the tungsten centers by cyclic voltammetry in aqueous solution. Electrochemical studies show the two or three stepwise cathodic/anodic peaks corresponding to the redox processes of WVI centers. The reversibility of redox peaks increases for [SiW11M(H2O)O39]6− and [PW11M(H2O)O39]5− polyoxometalates; however, that of [BW11M(H2O)O39]7− maintains quasi-reversible. The redox waves of the W-O framework for all polyoxometalates are pH- and scan rate-dependent. The tungsten-centered waves for these compound show a classical potential shift as a function of acidity at pH = 2.2–4.2. The electrocatalysis behaviors of these compounds toward the reduction of nitrite ions have been studied in details. The plots of catalytic efficiency versus γ for [XW11O39] n− and [XW11M(H2O)O39] m− (X = B, Si, P; MII = Mn, Co, Ni) show the catalytic efficiency of [BW11O39]9− and [BW11M(H2O)O39]7− (M = Mn, Co, Ni) more than that of the other compounds which are mentioned in this article. Graphical Abstract The electrochemical behavior of the XW11 and XW11M (X = B, Si and P; MII = Mn, Co and Ni) polyoxometalates has been investigated systematically in aqueous solution by cyclic voltammetry. Electrocatalytical reductions of nitrite ion by these compounds were investigated in detail
      PubDate: 2016-01-29
       
  • 3,8-Diaminobenzo[ c ]Cinnoline Derivatived Graphene Oxide Modified
           Graphene Oxide Sensor for the Voltammetric Determination of Cd 2+ and Pb
           2+
    • Abstract: Abstract Highly sensitive 3,8-diaminobenzo[c]cinnoline (3,8-DABCC) modified graphene oxide (GO) electrode was prepared, and it was denoted as pGO-DABCC. The electrode material was characterized with infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). pGO-DABCC on glassy carbon (GC/pGO-DABCC) electrode was investigated for simultaneous determination of Cd2+ and Pb2+ in aqueous media by differential pulse anodic stripping voltammetry (DPASV). Optimum conditions of the electrode were determined with some parameters such as constant potential, incubation time, pH, and volume of suspension on the electrode. The calibration equations for Cd2+ and Pb2+ determination were calculated as Ip(μA) = 0.3606[Cd2+] + 0.4346 with a correlation coefficient of 0.9972 and Ip(μA) = 0.2496[Pb2+] + 0.2878 with a correlation coefficient of 0.9968 (N = 5), respectively. The detection limits (LODs) for Cd2+ and Pb2+ were calculated as 0.12 and 0.21 μg/L, respectively. The remarkable results, such as good selectivity, repeatability, and reproducibility were obtained with the modified electrode. Application of the sensors to milk samples produced recovery values in the range 95 to 102 %.
      PubDate: 2016-01-23
       
  • Influence of Halide Ions on Anodic Oxidation of Ethanol on Palladium
    • Abstract: Abstract Ethanol oxidation on polycrystalline palladium electrodes in alkaline media was studied in the presence of halide ions. Addition of halide ions decreased the ethanol oxidation peak current monotonically as a function of increasing halide concentration. The extent of poisoning was found to be in the order I− > Br− > Cl−. Thus, Cl− ions show appreciable inhibition of ethanol oxidation peak current at [Cl−] ~ 10−3 M, whereas Br− and I− inhibit ethanol oxidation even at [Br−] or [I−] ~ 10−6 M. The potential of the ethanol oxidation peak shifted positive with increasing halide ion concentration. The extent of the shift was found to be in the order I− > Br− > Cl−. This study is relevant due to the widespread use of palladium halide complexes in the production of Pd electrocatalysts for ethanol oxidation and other electrocatalytic reactions.
      PubDate: 2016-01-11
       
  • Ammonia Oxidation at Electrochemically Platinum-Modified Microcrystalline
           and Polycrystalline Boron-Doped Diamond Electrodes
    • Abstract: Abstract The electrochemical oxidation of ammonia was done at electrochemically Pt-modified microcrystalline and polycrystalline boron-doped diamond (BDD) thin films from sp3 Diamond Technologies and Element Six. The Pt electrodepositions were done by chronoamperometry and cyclic voltammetry using a 1 mM K2PtCl6 solution in 0.5 M H2SO4. The Pt-BDD electrodes were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, and cyclic voltammetry. The Pt-BDD electrodes were compared by SEM and ammonia oxidation. At BDD electrodes, cyclic voltammetry depositions favors the formation of cubic and cauliflower Pt nanostructures at microcrystalline and polycrystalline BDD electrodes, respectively. On the other hand, chronoamperometry electrodeposition favors dendrite formation structures in both BDD electrodes. Platinum electrodeposited by chronoamperometry favors the formation of platinum (100) facets, which enhances ammonia oxidation. Pt-microcrystalline BDD showed the highest ammonia oxidation peak current densities when compared to Pt-polycrystalline BDD.
      PubDate: 2016-01-08
       
  • Effect of Core Composition in Au x Cu y @Pt/C for the Methanol Oxidation
           Reaction
    • Abstract: Abstract In this work, the effect of core composition in AuxCuy@Pt/C core@shell catalysts for methanol oxidation is investigated. The catalysts were prepared varying Au:Cu atomic percentage (i.e., 100:0, 75:25, 50:50, 25:75, and 0:100 %) while maintaining Pt constant. The average particle size of every sample was obtained from STEM measurements, while XRD measurements allowed to determining their crystal structure; in all cases, a FCC crystal structure was obtained. From chronoamperometry, it was found that the values of steady-state current density (I ss) increased with the gold content in the core, i.e., I ss values are 2.52, 1.86, 1.18, 0.34, and 0.18 mA cm−2 for Au100Cu0@Pt, Au75Cu25@Pt, Au50Cu50@Pt, Au25Cu75@Pt, and Au0Cu100@Pt, respectively. Similar results were obtained by using cyclic voltammetry, where the value of the peak current density increased as the gold content in the core increased: this behavior is associated to the modified electrochemical activity of Pt shell caused by the core composition (AuxCuy).
      PubDate: 2016-01-06
       
  • Surface and Catalytical effects on Treated Carbon Materials for Hydrogen
           Peroxide Electrogeneration
    • Abstract: Abstract This work focuses on the catalytic activity and surface modification of Vulcan XC 72R and Printex L6 toward the oxygen reduction reaction (ORR) after the carbon supports were subjected to a pre-treatment with nitric acid or ammonia. The results indicated that acid-treated Printex L6 was the best-suited material toward the two-electron pathway of the ORR. This material contained the largest concentration of oxygenated acid species and hydrogen, as determined by XPS, the Boehm method, and elemental analysis. The enhanced formation of H2O2 for acid-treated Printex L6 can be explained by the presence of oxygenated acid species increasing the hydrophilic character of the carbon support. The hydrophilicity of the material was investigated by contact angle measurements. However, the changes of the surface area, porosity, and the aliphatic chains of the carbons induced by the pre-treatments and the contributions of these factors to H2O2 production cannot be disregarded.
      PubDate: 2016-01-01
       
  • Evaluation of Polycrystalline Platinum and Rhodium Surfaces for the
           Electro-Oxidation of Aqueous Sulfur Dioxide
    • Abstract: Abstract Polycrystalline Rh and Pt were studied to ascertain their electrocatalytic activity for the electro-oxidation of SO2, an important reaction in sulfur dioxide depolarized electrolyzers used to produce hydrogen. Cyclic voltammetry and linear polarization methods were employed to evaluate the catalytic activity of these surfaces. Rh exhibited 25-fold lower catalytic activity than Pt and was more susceptible to poisoning by adsorbed intermediate sulfur species. Koutecky-Levich analysis indicated a two-electron transfer reaction on the Pt surface, which corresponded to the most commonly accepted SO2 electro-oxidation reaction mechanism. The Tafel slopes in the low potential region (near the onset potential), in conjunction with an analysis of well-known reaction mechanisms, suggested that the step leading to the oxidation of water to form adsorbed hydroxyl species was the rate-determining step (RDS). This mechanistic model predicts a decrease in Tafel slope with increasing coverage of catalyst active surface sites by adsorbed sulfur species. For Pt, we estimate a surface sulfur coverage of 4 % based on the experimentally measured Tafel slope. In the case of Rh, the sulfur coverage was calculated to be approximately 1 %. The Tafel slopes obtained changed from 106 mV decade−1 for Rh and 80 mV decade−1 for Pt at potentials below 0.7 V vs. standard hydrogen electrode (SHE) to 210 mV decade−1 for Rh and 162 mV decade−1 for Pt at potentials above 0.7 V vs. SHE, suggesting a change in the reaction mechanism corresponding to a change in the surface of the electrocatalyst.
      PubDate: 2016-01-01
       
  • The Effect of Rapid Thermal Annealing on Sputtered Pt and Pt 3 Pd 2 Thin
           Film Electrocatalysts for Aqueous SO 2 Electro-Oxidation
    • Abstract: Abstract Insight into the effect that rapid thermal annealing (RTA) has on the structural and electrochemical characteristics of sputtered Pt and Pt3Pd2 thin film electrocatalysts is communicated. The DC magnetron sputtered thin films were rapidly annealed at temperatures ranging from 600 to 900 °C under an Ar atmosphere. The microstructural changes and electrochemical properties (onset potential, current density and stability) induced by rapid thermal annealing were investigated towards the electro-oxidation of aqueous SO2. An increase in annealing temperature induced different degrees of crystallinity, and the surfaces changed from being smooth and granular to surfaces exhibiting defined grain boundaries. Electrochemical characterisation, employing linear polarisation (LP) and cyclic voltammetry (CV), revealed improved catalytic activity for the Pt3Pd2 thin film catalysts (compared to Pt) exhibiting lower onset potentials, competitive currents and acceptable stability. The Pt3Pd2 thin film, annealed at 800 °C, proved to be a promising contender in competing with pure Pt towards the electro-oxidation of aqueous SO2.
      PubDate: 2016-01-01
       
  • Effect of the OH − /Pt Ratio During Polyol Synthesis on Metal
           Loading and Particle Size in DMFC Catalysts
    • Abstract: Abstract A systematic variation of the molar ratio between hydroxide ions and platinum during polyol synthesis of Pt electrocatalysts supported on carbon nanotubes was conducted. The resulting materials were physically characterized by transmission electron microscopy, thermogravimetric analysis, and X-ray diffraction. It could be shown that precise control of the OH−/Pt ratio is necessary for achieving small-sized uniformly distributed Pt nanoparticles at high chemical yield. Simple adjustment of the pH value is not sufficient to control the reduction conditions since even small pH variations give rise to significant changes of the catalyst properties. The optimal OH−/Pt molar ratio was found to be 5:1 resulting in small particle size (ca. 2.5 nm in diameter) and high platinum loading (ca. 39 wt% at a nominal loading of 40 wt%). Moreover, we have shown that the developed electrocatalyst exhibits a high activity toward the oxygen reduction reaction which is confirmed by half-cell experiments in a rotating disk electrode and in single-cell experiments in direct methanol fuel cells.
      PubDate: 2016-01-01
       
  • Polymer of Intrinsic Microporosity Induces Host-Guest Substrate
           Selectivity in Heterogeneous 4-Benzoyloxy-TEMPO-Catalysed Alcohol
           Oxidations
    • Abstract: Abstract The free radical 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4B-TEMPO) is active as an electrocatalyst for primary alcohol oxidations when immobilised at an electrode surface and immersed into an aqueous carbonate buffer solution. In order to improve the catalytic process, a composite film electrode is developed based on (i) carbon microparticles of 2–12 μm diameter to enhance charge transport and (ii) a polymer of intrinsic microporosity (here PIM-EA-TB with a BET surface area of 1027 m2 g−1). The latter acts as a highly rigid molecular framework for the embedded free radical catalyst with simultaneous access to aqueous phase and substrate. The resulting mechanism for the oxidation of primary alcohols is shown to switch in reaction order from first to zeroth with increasing substrate concentration consistent with a kinetically limited process with competing diffusion of charge at the polymer layer-electrode interface (here the “LEk” case in Albery-Hillman notation). Reactivity optimisation and screening for a wider range of primary alcohols in conjunction with DFT-based relative reactivity correlation reveals substrate hydrophobicity as an important factor for enhancing catalytic currents. The PIM-EA-TB host matrix is proposed to control substrate partitioning and thereby catalyst reactivity and selectivity. Graphical Abstract The water-insoluble molecular alcohol oxidation catalyst 4-benzoyloxy-TEMPO is employed here embedded in a nano-composite film based on a hydrophobic polymer of intrinsic microporosity (PIM)
      PubDate: 2016-01-01
       
  • PtAu Electrocatalyst for Glycerol Oxidation Reaction Using a
           ATR-FTIR/Single Direct Alkaline Glycerol/Air Cell In Situ Study
    • Abstract: Abstract Different ratios of PtAu/C electrocatalysts were synthesized and assessed for their capability by glycerol electrooxidation. Electrocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), chronoamperometry, and direct glycerol/air fuel cell coupled with a ATR-FTIR setup. XRD of PtAu/C electrocatalysts showed the presence of Pt (fcc), Au (fcc), and PtAu (fcc) phases, and TEM images for PtAu/C electrocatalysts showed particle size between 5.4 and 5.8 nm. PtAu/C (50:50) presented the best result for glycerol electrooxidation by cyclic voltammetry and chronoamperommetry measurements in comparison with other electrocatalysts prepared. All PtAu/C showed better performance in comparison with Pt/C and Au/C. Moreover, the addition of gold to platinum favored glycerol by electronic effect and bifunctional mechanism. Through ATR-FTIR/direct alkaline glycerol/air cell in-situ study, it was possible to identify glycerate and tartronate as main products formed during the electrochemical glycerol oxidation.
      PubDate: 2016-01-01
       
  • Study of 2-Propanol, 1-Propanol, and Acetone Electrochemical Oxidation on
           Pt in Gelled Phosphoric Acid at 170 °C
    • Abstract: Abstract Electrochemical oxidation of acetone, 2-propanol, and 1-propanol on Pt was studied by slow scan rate voltammetry at 170 °C using fuel cell with the membrane of the H3PO4 doped polybenzimidazole. Reaction rate orders with respect to partial pressures of the aliphatic compounds and water vapors were determined at E = 0.5 V and at E = 0.9 V, which correspond to low and high surface oxide coverages on Pt. At E = 0.5 V close to zero reaction rate orders in respect to vapor pressures of aliphatic reactants were found. At E = 0.5 V reaction, rate orders with respect to water vapor pressure were slightly higher than unity in all cases. At E = 0.9 V oxidation, reaction rate orders with respect to aliphatic reactant vapor pressure ranged within 0.6–1. Close to zero reaction rate orders with respect to water vapor pressure were found in all cases at E = 0.9 V.
      PubDate: 2016-01-01
       
  • Analysis of the Corrosion Kinetic of Pt/C Catalysts Prepared on Different
           Carbon Supports Under the “Start-Stop” Cycling
    • Abstract: Abstract A series of 50 wt% Pt/C catalysts based on carbon blacks with different specific surface areas and morphologies was synthesized and investigated using “start-stop” protocol (triangular scan in the 1.0–1.5 V vs. reversible hydrogen electrode (RHE) potential range with a scan rate of 500 mV s−1). The commercial 40 wt% Pt/Vulcan XC-72 and 50 wt% Pt/TEC were used for comparison. The oxygen reduction reaction (ORR) activities and electrochemically active surface area (ECSA) of Pt were obtained at 25 °C in 0.1 M HClO4 electrolyte after every 4000 cycles. All synthesized Pt/C catalysts were characterized by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), low-temperature nitrogen sorption, CO pulse chemisorption methods, and cycling voltammetry including a rotating disc electrode (RDE) method for analysis of the ORR kinetics. Dependences of the ORR activities, ECSA, and values of Tafel slopes on the number of oxidative cycles were obtained and analyzed in detail. It was shown that the initial values of Tafel slopes of the Pt/C catalysts decrease with increase of the surface area of carbon blacks. The increase in the values of Tafel slopes in the high-current density region with cycling was associated with the degradation of carbon support. The reciprocal ratios of the ECSA to initial values were found to grow linearly on the number of cycles. The ORR surface activity was significantly decreased in the first 8000–10,000 oxidation cycles as the result of changes of the active component and carbon support degradation. The following slight increase in the ORR surface activities with cycling was related to the increase in the Pt particle sizes in the Pt/C catalysts. Modification of Ketjen black EC 600 DJ through pyrocarbon deposition (KB600-C sample) led to appreciable increase of the stability of the Pt/KB600-C sample.
      PubDate: 2015-12-22
       
  • The Electrooxidation of Formic Acid on Pd Nanoparticles: an Investigation
           of Size-Dependent Performance
    • Abstract: Abstract Palladium nanoparticles (Pd NPs) were deposited on highly oriented pyrolytic graphite (HOPG) substrates by using a potentiostatic double-pulse technique. The NPs possessed a narrow size distribution and wide dispersion. The particle density was in the order of 109 cm−2. The average height of Pd NPs was controlled in a range of 3 to 50 nm by adjusting the duration of growth pulse. The carbon monoxide (CO) stripping at Pd NPs smaller than 14 nm occurred predominantly at a potential above 1.1 V, which is around 0.2 V more positive than that at bulk Pd and larger Pd NPs, due to the small Pd NPs tending to possess well-ordered (111) facets and a high ratio of edge and corner atoms. The high coverage of adsorbed CO (COads) at small Pd NPs can block the formation of adsorbed hydroxyl (OHads) and drive up the oxidation potential. During formic acid oxidation (FAO), small Pd NPs were quickly poisoned by CO, which was formed initially at edges and corner atoms by electrochemical reduction of FAO product CO2 at low potentials. Based on the overall consideration of the low CO tolerance and the high difficulty to remove CO, it must be stated that Pd NPs smaller than 15 nm without strict shape control are not well suited for FAO.
      PubDate: 2015-12-10
       
  • Electrochemical Evaluation of Pt-Based Binary Catalysts on Various
           Supports for the Direct Methanol Fuel Cell
    • Abstract: Abstract Multi-walled carbon nanotubes (MWCNTs), TiO2, MoO2, and carbon black Vulcan XC-72 were investigated as supports for PtRu and PtSn catalysts. X-ray diffraction (XRD) confirmed that all electrocatalysts examined display characteristic patterns similar to that of the Pt/C electrocatalyst, an indication that the catalysts have predominantly the Pt face-centered cubic (fcc) crystal structure. High-resolution transmission electron microscopy (HRTEM) images showed spherical PtRu and PtSn nanoparticles with a narrow particle size distribution, dispersed on the support materials. The metal loading for the prepared electrocatalyst was estimated using energy-dispersive X-ray spectroscopy (EDS), and it was observed to be closest to that of the catalysts supported on Vulcan XC-72. Cyclic voltammograms showed PtSn/C to be the most active, as it possessed a higher electroactive surface area than that of the other catalysts, followed by Pt/C > PtRu/MWCNT > PtRu/C > PtSn/MWCNT > PtSn/MoO2 > PtRu/MoO2 > PtSn/TiO2 > PtRu/TiO2. It was also observed that catalysts supported on MWCNTs were more active than those supported on metal oxides. Furthermore, catalysts supported on MWCNTs proved to be more stable than all the other supported catalysts examined. Therefore, MWCNTs have been proven in this study to be the best material for supporting electrocatalysts for direct methanol fuel cells.
      PubDate: 2015-11-05
       
  • In Situ IR Studies on the Electro-Oxidation of Cyanide on Ni, Cu and Au
           Electrodes Electrically Polarized in Dimethyl Sulfoxide (DMSO) Electrolyte
           Media
    • Abstract: Abstract Subtractively normalised Fourier transform infrared spectroscopy (SNIFTIRS) studies are reported on the electrical polarisation of nickel (Ni), copper (Cu) and gold (Au) electrodes in KCN dissolved in the polar aprotic solvent, dimethyl sulfoxide (DMSO) with tetrabutyl ammonium perchlorate (TBAP) (0.1 mol L−1) as supporting electrolyte. These studies have shown clearly that each of the metal electrodes investigated oxidised (as the applied potential was adjusted in an anodic direction) to form Ni(II), Cu(I) and Au(I)-cyano complex ions of [Ni(CN)4]2−, [Cu(CN)3]2−, [Cu(CN)2]− and [Au(CN)2]−. The distribution of other electro-oxidation products of cyanide observed, namely KOCN(s) and CO2 depended on the electrode under consideration. For Ni electrodes, DMSO-solvated CO2 and solid KOCN were observed together as the oxidation products while on Cu and Au electrodes CN− was oxidised to DMSO-solvated CO2 exclusively without any solid cyanate salt film deposition being simultaneously observed. Cu was found to be particularly electrocatalytic towards the electro-oxidation of CN− ion to CO2 with high current density values being observed. It is proposed that the metal-cyano complex ion species observed in SNIFTIRS experiments are implicated in the oxidation mechanism of CN− to KOCN and/or CO2 on these electrodes, particularly on the Cu and Au electrodes. This resembled the electrochemistry observed in similar systems involving the electrochemical oxidation of cyanide on Cu electrodes in aqueous media.
      PubDate: 2015-10-12
       
  • Electrochemical Reduction of CO 2 on Ni- and Pt-Epitaxially Grown Cu(111)
           Surfaces
    • Abstract: Abstract The electroreduction of CO2 on well-defined M/Cu(111) (M = Ni and Pt) bimetallic surface systems fabricated using molecular beam epitaxy was studied. The total faradic efficiency for CO2 reduction using one-monolayer (ML)-thick Pt epitaxially grown on a Cu(111) substrate (1-ML Pt/Cu(111)) was nearly the same as that for clean Pt(111). In contrast, the 1-ML-thick Ni/Cu(111) system exhibited increased selectivity for CH4 production compared with that of clean Ni(111), which may stem from the geometric tensile strain induced by the underlying Cu(111) substrate. Notably, bimetallic surfaces consisting of 0.1-ML-thick Ni or Pt grown on Cu(111) exhibited significantly different reduction behaviors compared with those of Cu because of the presence of the a small amount of epitaxially grown metal. For the 0.1-ML-thick Ni/Cu(111) system, the total faradaic efficiency for CO2 reduction and the production rate for CO were enhanced compared with those for clean Cu(111), whereas the production of CH4 decreased. In contrast, the total faradaic efficiency was significantly suppressed for the 0.1-ML-thick Pt/Cu(111) bimetallic substrate, with only a very small amount of CH4 production. The difference in the catalytic properties is attributed to the difference in the adsorption energies for CO, which is an intermediate in the electrochemical production of CH4 and C2H4.
      PubDate: 2015-10-07
       
  • Evaluating Activity for Hydrogen-Evolving Cobalt and Nickel Complexes at
           Elevated Pressures of Hydrogen and Carbon Monoxide
    • Abstract: Abstract Molecular cobalt and nickel complexes are among the most promising homogeneous systems for electrocatalytic hydrogen evolution. However, there has been little exploration into the effect of gaseous co-additives such as CO and H2, which may be present in operating hydrogen-evolving or carbon-dioxide reduction systems, on the performance of these molecular electrocatalysts. In this report, we investigate the electrocatalytic activity of six cobalt and nickel complexes supported by tetraazamacrocyclic or diazadiphosphacyclooctane ligands for the reduction of p-toluenesulfonic acid to hydrogen in acetonitrile under inert atmosphere and in the presence of CO and H2. We present an elevated-pressure electrochemical apparatus capable of reaching CO and H2 pressures of ca. 15–520 pounds per square inch (psia) (∼1–35 atm), and we use this apparatus to determine binding constants for CO addition for each catalyst and study the inhibition of the electrocatalysis as a function of CO and H2 pressure. In the case of CO, the extent of catalytic inhibition is correlated to the binding constant, with the cobalt complexes showing a greater degree of catalyst inhibition compared to the nickel complexes. In the case of H2, no complex showed appreciable electrocatalytic inhibition even at H2 pressures of ca. 500 psia.
      PubDate: 2015-10-05
       
  • Effect of Gold Modification with 3-Mercaptopropionic Acid, Cysteamine and
           Gold Nanoparticles on Monoethanolamine Electrooxidation
    • Abstract: Abstract In this work, a gold electrode modified with self-assembled layers (SAMs) composed of 3-mercaptopropionic acid, cysteamine and gold nanoparticles was prepared. The electrode with SAMs endowed with gold nanoparticles gave the high catalytic effect for monoethanolamine (MEA) electrooxidation in solution at pH 7. For this novel sensor, a linear relationship between the current response of MEA at the potential of peak maximum (j p) and the concentration of this compound in solution (c MEA) was found, over the range 0.1 μM to 0.8 M with the detection sensitivity equal to about 5 A cm−2 mol−1 dm3 (at v = 0.1 V s−1) and the detection limit of 0.046 μM.
      PubDate: 2015-10-02
       
 
 
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