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Journal Cover   Electrocatalysis
  [SJR: 0.883]   [H-I: 10]   Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1868-2529 - ISSN (Online) 1868-5994
   Published by Springer-Verlag Homepage  [2291 journals]
  • The Formation of Surface Oxides on Nickel in Oxalate-Containing Alkaline
    • Abstract: Abstract The electrochemical formation of α-Ni(OH)2 and NiOOH in the presence of adsorbed oxalate in alkaline media is studied under well-controlled experimental conditions that include the variation of the system temperature (T = −10 to 20 °C), the scan rate (v = 20, 150, and 200 mV s−1), and the concentration of supporting electrolyte (0.10 and 0.50 M KOH). The studies are carried out using cyclic voltammetry (CV) with polycrystalline bulk nickel and nickel foams. In situ infrared spectroscopy with voltammetry confirms the adsorption of oxalate to the surface of nickel in the 0.10 to 0.30 V potential window, concurrent with the formation of the α-Ni(OH)2 species. The presence of oxalate in the system increases the charge density (Q) for the formation of both the α-Ni(OH)2 and NiOOH surface oxides. The Q values calculated under various conditions indicate that the presence of oxalate in the system encourages the formation of a full single monolayer (ML) of NiOOH in the first CV scan. Measurements carried out at room temperature demonstrate that an increase in v decreases the Q values for NiOOH in the presence of oxalate to minimum values achieved at v ≥150 mV s−1. An increase of KOH concentration results in the formation of a thicker layer of NiOOH both in the presence and absence of oxalate. The Q values of NiOOH reduction in conditions that favor the formation of one complete monolayer of NiOOH are used to calculate the specific surface areas of open-cell nickel foams. The calculation of electrochemical surface area using this method is discussed and evaluated with respect to calculations based on the charge of α-Ni(OH)2 formation.
      PubDate: 2015-07-30
  • Ordered Intermetallic Nanostructured PtSb/C for Production of Energy and
    • Abstract: Abstract This paper has evaluated ordered intermetallic nanostructured PtSb/C as anode for glycerol electrochemical oxidation in both acidic and alkaline media. Nanostructured PtSb/C performed as well as and 50 % better than commercially available Pt/C nanoparticles in acidic and basic media, respectively. The presence of Sb atoms in the material structure enhanced C-C bond cleavage activation in alkaline medium. Spectroelectrochemical studies confirmed that the reactions conducted in acidic and alkaline solutions produced high-value chemicals. Depending on the nature of the employed electrolyte, the nanostructured PtSb/C material can potentially afford interesting compounds for the chemical industry or even generate electrical energy.
      PubDate: 2015-07-28
  • Enhanced Oxygen Reduction Reaction Activity with Electrodeposited Ag on
           Manganese Oxide–Graphene Supported Electrocatalyst
    • Abstract: Abstract Manganese oxide-modified graphene nanosheet-supported silver nanocatalyst (Ag-MnOx/G) was prepared via two-step chemical and electrochemical deposition. Surface characterization of the prepared Ag-MnOx/G catalyst was performed by X-ray photoelectron spectroscopy, scanning electron microscopy, as well as X-ray fluorescence techniques, and the electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline media was studied using cyclic voltammetry and the rotating disk electrode (RDE) method. The onset potential of the ORR of the prepared catalyst material shifted positive about 40 mV, and the half-wave potential 20 mV compared to those of the bulk Ag electrode. After 1000 potential cycles between 0.05 and 1.1 V for accelerated aging tests, high stability of the Ag-MnOx/G catalyst in the ORR was observed with the half-wave potential of the ORR shifting negatively only about 0.04 V. RDE studies displayed unconditional improvement of electrochemical activity and long-term durability for the Ag-MnOx/G composite material.
      PubDate: 2015-07-23
  • Influence of Vanadium Ions on the Degradation Behavior of Platinum
           Catalysts for Oxygen Reduction Reaction
    • Abstract: Abstract The vanadium air redox flow battery is a combination of a redox flow battery and a reversible fuel cell. For the oxygen reduction during discharge, platinum (Pt) catalysts are common. During operation, vanadium (V) cations can penetrate through a proton exchange membrane into the water/air half-cell. The aim of the present work is to study whether V compounds are deposited on the Pt surface under operation conditions or whether the V ions influence the stability of Pt in any other way. Thereby, bulk platinum electrodes are compared as a simple model system to carbon-supported Pt nanoparticles via cyclic voltammetry. In the case of bulk platinum, electrochemical quartz crystal microbalance measurements showed no deposition of vanadium compounds but indicated the decrease of the (hydr)oxide layer on Pt above V3+ and VO2+ redox potentials. Cycling 100 times between oxygen reduction and oxygen evolution potentials with and without a heavy V contamination did not lead to significant degradation of the model catalyst and shows no influence of V ions. On the contrary, the nanoparticle-based catalyst significantly degraded during the same stability protocol. The V contamination lowered the degradation in this case.
      PubDate: 2015-07-15
  • Influence of CeO 2 on Pt-Pd/CeO 2 -OMC Catalysts for Formic Acid Oxidation
    • Abstract: Abstract This article deals with the promotional effects of CeO2 on PtPd/CeO2-OMC electrocatalysts. The synthesized catalysts are characterized using different physicochemical techniques and evaluated in a formic acid oxidation fuel cell. N2 adsorption/desorption analysis shows that CeO2 modification increases the surface area of OMC from 1005 to 1119 m2/g. SEM, XRD, and TEM analysis reveal that the presence of CeO2 enhances the active metal(s) dispersion on the CeO2-OMC surface. The average particle size of the dispersed metal decreases with the increase of Pt/Pd ratio on CeO2-OMC support. Cyclic voltametry measurement of Pd/CeO2-OMC gives 12 % higher anodic current activity with 83-mV negative shift of the peak E as compared to unmodified Pd/OMC. In bimetallic catalysts, the addition of Pt improves the activity and stability of the catalysts significantly. Among the bimetallic samples, Pd3Pt1/CeO2-OMC displays superior current density (74.6 mA/cm2), which is 28.3 times higher than that of Pt/CeO2-OMC. It also shows higher stability (on 32.8 mA/cm2) for an extended period of time (30 min) with least indication of CO poisoning effects.
      PubDate: 2015-07-01
  • Nickel Complexes Based on Thiophosphorylated Calix[4]Resorcinols as
           Effective Catalysts for Hydrogen Evolution
    • Abstract: Abstract Nickel complexes of thiophosphorylated calix[4]resorcinols showed high catalytic activity for hydrogen evolution from acidic solutions and stability in the electro-assisted catalysis at the surface of both glassy carbon and Hg-pool electrodes. The conformation of the macrocyclic ligand determines the dimensionality and shape of the catalytically active species generated on the electrode.
      PubDate: 2015-07-01
  • Electrochemical Fabrication of Well-Defined Spherical Iridium
           Nanoparticles and Electrocatalytic Activity towards Carbon Monoxide
           Adlayer Oxidation
    • Abstract: Abstract This study outlines the methodology to electrodeposit well-defined iridium nanospheres onto glassy carbon (GC) electrodes at room temperature, using a square wave potential (SWP) technique. Similar work has recently been carried out for other noble metal nanoparticles, in particular platinum and palladium. In this study, particle size and Ir loading can be controlled by altering two key parameters in the electrodeposition process; the nucleation potential and the growth duration. Ir nanoparticles were characterized using cyclic voltammetry (CV) and scanning electron microscopy (SEM). It was found that the nucleation potential and time influence not only the nucleation density but also the particle size. In addition, the electrochemical activity of the particles towards carbon monoxide (CO) adlayer oxidation was investigated as a surface test reaction. The results showed that surface morphology of the deposited particles, which could be altered using potential cycling, plays a pivotal role in determining the activity of the particles. Particles that were treated by potential cycling showed a significantly lower overpotential, in contrast to particles of similar size that were untreated. This indicates an enhancement in electrocatalytic activity due to the enrichment of surface defects.
      PubDate: 2015-07-01
  • Direct Electrochemistry of Glucose Oxidase on a Three-Dimensional Porous
           Zirconium Phosphate–Carbon Aerogel Composite
    • Abstract: Abstract Biocompatible materials with large specific surface areas can play a crucial role in direct electron transfer between redox proteins and an electrode surface. Here, we report zirconium phosphate–carbon aerogel (ZrP-CA) composites with a large specific surface area and uniform nanopore distributions as matrix for glucose oxidase immobilization. The immobilized glucose oxidase displays two stable, well-defined redox peaks with an electron transfer rate constant of 9.34 s−1 in nitrogen-saturated phosphate-buffered saline (PBS) solution (0.1 M, pH 7.0), at a scan rate of 100 mV s−1. The modified electrode was also used as a glucose biosensor, which was found to exhibit a linear calibration range of 0.12–2.0 mM, sensitivity of 5.56 μA mM−1 cm−2 at an applied potential of −0.5 V, and detection limit of 34 μM based on a signal-to-noise ratio of 3. After 80 scan cycles, the decreases in the peak current were less than 8 %, indicating good stability of the as-prepared ZrP-CA. The unique characteristics of the ZrP-CA nanocomposite make it a good matrix for protein immobilization and biosensor preparation.
      PubDate: 2015-07-01
  • Kinetic Investigations of Glycerol Oxidation Reaction on Ni/C
    • Abstract: Abstract This study evaluates the electrochemical oxidation of glycerol using a nickel-supported catalyst under several well-defined experimental conditions. The influence of scan rate, temperature, glycerol, and NaOH concentrations were systematically investigated. The slope of the log-log relationship of the anodic peak current for glycerol oxidation as a function of the scan rate indicates that the electrochemical glycerol oxidation is a complex mechanism partially limited by diffusion-controlled process. This is in agreement with the temperature effect on glycerol oxidation, since the slope value associated with the relationship between the logarithm of the current density of the anodic peak and the inverse of temperature also indicates a diffusion process. When the glycerol concentration increases, the peak associated to its oxidation also increases, but it seems to reach a limit. This behavior was associated with two main effects, i.e., the saturation of the active catalytic sites on the electrode surface and the change in the glycerol oxidation mechanism as demonstrated by FTIR spectroscopic measurements.
      PubDate: 2015-06-05
  • Achievements and Trends in Photoelectrocatalysis: from Environmental to
           Energy Applications
    • Abstract: Abstract The great versatility of semiconductor materials and the possibility of generation of electrons, holes, hydroxyl radicals, and/or superoxide radicals have increased the applicability of photoelectrocatalysis dramatically in the contemporary world. Photoelectrocatalysis takes advantage of the heterogeneous photocatalytic process by applying a biased potential on a photoelectrode in which the catalyst is supported. This configuration allows more effectiveness of the separation of photogenerated charges due to light irradiation with energy being higher compared to that of the band gap energy of the semiconductor, which thereby leads to an increase in the lifetime of the electron-hole pairs. This work presents a compiled and critical review of photoelectrocatalysis, trends and future prospects of the technique applied in environmental protection studies, hydrogen generation, and water disinfection. Special attention will be focused on the applications of TiO2 and the production of nanometric morphologies with a great improvement in the photocatalyst properties useful for the degradation of organic pollutants, the reduction of inorganic contaminants, the conversion of CO2, microorganism inactivation, and water splitting for hydrogen generation.
      PubDate: 2015-06-04
  • PdAu/C Electrocatalysts as Anodes for Direct Formate Fuel Cell
    • Abstract: Abstract PdAu/C electrocatalysts in different atomic ratios (90:10, 80:20, 70:30, and 50:50) supported on Vulcan XC72 carbon were evaluated toward formate oxidation in alkaline media. The materials were prepared by the borohydride process. X-ray diffraction (XRD) patterns of PdAu materials showed peak characteristic of Pd and Au face-centered-cubic (fcc) structures while transmission electron micrographs (TEM) showed the nanoparticles with particle size between 4 and 10 nm for all electrocatalysts. Experiments considering single cell suggested the PdAu/C (90:10) and PdAu/C (80:20) as promisors for formate oxidation. The best result obtained was attributed to the presence of Au in small quantities that contributes to the formate adsorption.
      PubDate: 2015-05-31
  • Co 3 O 4 Nanorods—Efficient Non-noble Metal Electrocatalyst for
           Oxygen Evolution at Neutral pH
    • PubDate: 2015-05-31
  • Electrocatalytic Reduction of Carbon Dioxide using Sol-gel Processed
           Copper Indium Sulfide (CIS) Immobilized on ITO-Coated Glass Electrode
    • Abstract: Abstract Sol-gel processed copper indium sulfide (CIS) films have been processed on glass and transparent indium doped tin oxide (ITO)-coated glass electrodes by a straightforward layer by layer spin coating route yielding excellent film qualities with subsequent thermal annealing. Resulting films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-vis spectroscopy. We apply these films in an electrochemical cell as a working electrode and take a view on the reduction of carbon dioxide (CO2) to its energy richer carbon monoxide (CO) in acetonitrile solution containing 0.1 M (C4H9)4NPF6 supporting electrolyte saturated with CO2. CIS films exhibit pronounced electrochemical and photoelectrochemical activities. Concomitantly, we quantify the generation of CO, which starts to evolve at a threshold potential of −0.60 V vs normal hydrogen electrode (NHE). The calculated faradaic efficiency of the electrochemical reduction of CO2 into CO exceeds 20 (±1) % in an optimized thin-film structure. Graphical Abstract Sol-gel processed copper indium sulfide (CIS) thin films have been processed on glass and indium doped tin oxide (ITO)-coated glass electrodes using layer by layer spin coating route yielding excellent film qualities with subsequent thermal annealing. Electrochemical and photoelectrochemical experiments performed in N2 and CO2 saturated acetonitrile solutions containing 0.1 M (C4H9)4NPF6 as an electrolyte and CIS-modified ITO as working electrode showed promising electrocatalytic and photoelectrocatalytic activity for the reduction of carbon dioxide (CO2) to its energy richer carbon monoxide (CO) with faradaic efficiency of about 20 (±1) %.
      PubDate: 2015-05-20
  • Structure and Surface Reactivity of Ultra-Thin Pt/W(111) Films
    • Abstract: Abstract We report on the structure, the chemisorption and the electrocatalytic properties of multilayer (2.2, 3.3 and 5.5 physical monolayers) Pt films deposited on W(111) elaborated by molecular beam epitaxy. The Pt/W(111) surfaces were characterized by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Pronounced changes of the surface reactivity were noticed as the Pt coverage is decreased. In particular, the affinity for under-potentially deposited hydrogen (Hupd) and hydroxyl (OHads) species and the ability to electrooxidize a monolayer of COads were depreciated in agreement with strain and ligand effects.
      PubDate: 2015-05-19
  • Synthesis, Characterization, and Application of Exfoliated
           Graphite/Zirconium Nanocomposite Electrode for the Photoelectrochemical
           Degradation of Organic Dye in Water
    • Abstract: Abstract We report the synthesis and application of a novel exfoliated graphite–zirconium oxide nanocomposite photoanode for the photoelectrochemical degradation of eosin yellowish dye in water. Zirconium oxide nanoparticle was synthesized by sol–gel, method and EG–ZrO2 nanocomposite was synthesized by wet solution method. The materials were characterized by scanning electron microscopy, thermogravimetry and differential thermal analysis (TGA-DTA), Brunauer–Emmett–Teller (BET) surface area analysis, and X-ray diffraction (XRD). Applicability of the EG–ZrO2 as photoanode material was investigated by the photoelectrochemical degradation of eosin yellow as a model for organic pollutants in 0.1 M Na2SO4 (pH 7) solution at a current density of 5 mA cm−2 after optimizing the EG–ZrO2 loading. The FTIR, XRD, and Raman data showed the formation of the nanocomposite. The XRD patterns show that the ZrO2 nanoparticle contains mainly the monoclinic phase as complemented by Raman spectroscopy. Photoelectrochemical studies with the EG–ZrO2 nanocomposite showed a significant decrease in the initial dye concentration (20 ppm) compared with the bare exfoliated graphite (EG) and zirconium oxide (ZrO2) only. The results indicate that the ZrO2 nanoparticle in the EG–ZrO2 composite enhanced the degradation efficiency of the EG substrate. Thus, EG–ZrO2 composite can be used for the photoelectrochemical oxidation of organic pollutants, especially organic dyes.
      PubDate: 2015-05-08
  • The Effect of Reducing Agents on the Electronic, Magnetic and
    • Abstract: Abstract The electronic, magnetic and electrocatalytic properties of bimetallic thiol-capped Pt/Co and Pt/Ni nanoparticles were synthesised using two reducing agents, NaBH4 and N2H4. X-ray diffraction analysis of the nanoparticles showed Pt lattice contraction upon the addition of Co or Ni to Pt indicating the formation of an alloy structure, more apparent when N2H4 was used. XPS data analysis revealed Pt metal and Pt(II) (assigned to PtO) and a higher concentration of surface metallic Ni and Co for the NaBH4-reduced samples. Both the NaBH4- and N2H4-reduced catalysts were active for the methanol oxidation reaction (MOR), with the Pt-Co-N2H4 catalyst revealing the highest activity. The N2H4 significantly affected the magnetic properties of Pt/Co and Pt/Ni particles by controlling the morphology and crystalline structure of the nanoparticles. In general, the type of reducing agent affected the final properties of the nanoparticles.
      PubDate: 2015-05-01
  • Electro-Oxidation of Nitrite Using an Oxidized Glassy Carbon Electrode as
           Amperometric Sensor
    • Abstract: Abstract In this work, a simple and innovative method is proposed to get an active glassy carbon electrode (GC) toward nitrite oxidation. The oxidation method was based on an anodic treatment, through a time- and potential-controlled electrolysis, in NaOH 0.1 M. This treatment increased the activity in all pH values that were studied, being the pH 8.0 as the best one. It was possible to calculate the kinetic parameters, where the number of transferred electrons calculated was one, and Tafel slope was 70 mV per decade. With these values, a reaction mechanism was postulated. At the best experimental conditions, the electrode has a good behavior as an amperometric sensor versus nitrite oxidation. The system follows linearity in all the range of concentrations and allowed the calculation of analytical parameters such as detection limit, quantification limit, accuracy, and exactitude. Good results were obtained at this point, so the system might be considered a good method for nitrite determination and quantification in aqueous solutions.
      PubDate: 2015-05-01
  • The Influence of Protonation on the Electroreduction of Bi (III) Ions in
           Chlorates (VII) Solutions of Different Water Activity
    • Abstract: Abstract We examined the electroreduction of Bi (III) ions in chlorate (VII) solutions under varied protonation conditions of the depolariser using voltammetric and impedance methods. The results of the kinetic parameter correlation lead to the statement that the changes in the amount of chloric (VII) acid against the amount of its sodium salt in the supporting electrolytes of the low water activity have a significant influence on the rate of Bi (III) ion electroreduction. The increase of the concentration of chloric acid sodium salt, as well as the chloric (VII) acid alone within the particular concentration of the supporting electrolyte, inhibits the process of Bi (III) ion electroreduction. It should be associated with the reorganisation of the structure of the double layer connected with the slow dehydration inhibited by ClO 4 − ions. The standard rate constants k s values with the increase of the chlorate (VII) concentrations for all the solutions examined of chlorates (VII) confirms the catalytic influence of the decrease of water activity on the process of Bi (III) ion electroreduction. The multistage process is confirmed by the non-rectilinear 1nk f = f(E) dependences.
      PubDate: 2015-05-01
  • Electrochemical Quartz Crystal Microbalance Determination of Nickel Formal
           Partial Charge Number as a Function of the Electrode Potential upon Nickel
           Underpotential Deposition on Platinum in Sulfuric Medium
    • Abstract: Abstract Although nickel underpotential deposition (UPD) on platinum surfaces has been demonstrated in sodium sulfate media, there is no consensus regarding the value of nickel formal partial charge number (ι Ni) upon adsorption on platinum. Moreover, in most studies, nickel formal partial charge number is determined as an average, calculated on the whole Ni-UPD potential range (i.e., for NiUPD coverage values varying between approximately 0 and 1). In the present contribution, the electrochemical quartz crystal microbalance technique is employed to go beyond this average ι Ni determination. A simple method is proposed to evaluate the electrode-potential-dependent (i) variations of the surface coverages of the specifically adsorbed species and (ii) corresponding nickel formal partial charge number upon adsorption on platinum. From the values of the surface coverage of the adsorbing species, one can recalculate the current densities during the anodic sweep of the cyclic voltammogram. These recalculated current densities agree with the experimental data, which validates the method. The value of the nickel formal partial charge number (ι Ni) decreases upon electrode potential increase, suggesting enhanced sulfate co-adsorption at high Ni-UPD potential. This further enables to determine the potential of zero total charge (PZTC) of the platinum electrode in the considered sulfate-containing electrolyte solutions: The presence of nickel shifts the PZTC of platinum positively by ∼100 mV compared to supporting electrolyte, in agreement with the presence of specifically adsorbed cations.
      PubDate: 2015-04-17
  • One-Pot Hydrothermal Synthesis of Reduced Graphene Oxide–Multiwalled
           Carbon Nanotubes Composite Material on Nickel Foam for Efficient
           Supercapacitor Electrode
    • Abstract: Abstract The reduced graphene oxide/multiwalled carbon nanotubes deposited on nickel foam (rGO/MWCNTs/NF) composite material was successfully prepared using one-pot hydrothermal method. The prepared rGO/MWCNTs/NF composite material was characterized using scanning electron microscopy, electron dispersive spectroscopy, and Raman spectroscopy. The results show that MWCNTs were successfully incorporated into the graphene sheets uniformly. The rGO/MWCNTs/NF composite material was fabricated as electrode for supercapacitor application. The capacitive properties of the rGO/MWCNTs/NF composite material were studied using electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge in 1 M KOH aqueous electrolyte solution. The rGO/MWCNTs/NF electrode showed enhanced capacitance compared to rGO/NF, MWCNTs/NF, and bare NF electrodes due to high surface area and more accessibility of electrolyte after the addition of MWCNTs to the rGO/NF electrode. The rGO/MWCNTs/NF composite material shows specific capacitance of 81.14 F g−1 at current density of 1 A g−1 and excellent cycling stability with 83 % of its initial capacitance after 1000 charge/discharge cycles.
      PubDate: 2015-04-11
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