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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  [2302 journals]
  • 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
       
  • CeO 2 Nanotubes Supported Pd Electrocatalysts for Formic Acid Oxidation
    • Abstract: Abstract CeO2 nanotubes with well-defined hollow interiors are employed as support material for Pd electrocatalysts towards formic acid oxidation (FAO). Pd nanoparticles are deposited both on the outer surfaces and inside interiors of CeO2 nanotubes. The as-prepared Pd catalysts possess a large electrochemical surface area (ESA) and exhibit improved electrocatalytic performance towards FAO in comparison with the Vulcan XC-72 carbon black and the commercial CeO2 powder supported Pd catalysts.
      PubDate: 2015-05-01
       
  • The Hydrogen Evolution Reaction on Rhenium Metallic Electrodes: A Selected
           Review and New Experimental Evidence
    • Abstract: Abstract The volcano plots reported in the field of electrocatalysis utilize data with a difference of three orders of magnitude between the worst and the best rhenium electrocatalytic activity toward the hydrogen evolution reaction (HER). However, the commonly used mean value of the exchange density current (j 0) of the HER on rhenium is log j 0 = −2.9 A cm−2, which is higher than the value used for platinum (log j 0 = −3.3 A cm−2). This fact seems to contradict Sabatier’s principle and points to the possibility that this value corresponds more to rhenized surfaces than to metallic rhenium. Rhenized surfaces are primarily composed of a mixture of oxides; therefore, the electrocatalytic behavior is attributed to these thin films rather than to metallic rhenium. In addition, a selected review of rhenized electrodes is included herein because these issues have not been considered in the electrocatalysis literature at the present time. We initially believed that the kinetic parameters might have been overestimated due to the formation of rhenide ion or rhenium hydride species; however, no evidence of the formation of these species was found. Our experimental mean value of the exchange current density of the HER on metallic rhenium is 7 × 10−5 A cm−2 in acidic solution. Therefore, our results are in accordance with Sabatier’s principle, which states that a weak adsorption energy of hydrogen on rhenium (energy, 6.9 kJ mol−1) results in a slow rate of reaction (log j 0 = −4.2 A cm−2), whereas an intermediate adsorption energy of hydrogen on platinum (12 kJ mol−1) produces a fast reaction (log j 0 = −3.3 A cm−2).
      PubDate: 2015-05-01
       
  • Electrochemical Synthesis of Ammonia Based on Co 3 Mo 3 N Catalyst and
           LiAlO 2 –(Li,Na,K) 2 CO 3 Composite Electrolyte
    • Abstract: Abstract Cobalt molybdenum nitride (Co3Mo3N) catalyst was synthesised through ammonolysis of the corresponding precursors by flowing pure ammonia gas. The catalyst was characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ammonia was successfully synthesised from wet hydrogen and dry nitrogen at atmospheric pressure using Co3Mo3N–Ag composite as cathode, Ag–Pd alloy as anode and LiAlO2–(Li/Na/K)2CO3 composite as an electrolyte. Ammonia formation was investigated at 400, 425 and 450 °C, and the maximum observed ammonia formation rate was 3.27×10−10 mol s−1 cm−2 at 450 °C when applied at 0.8 V. The catalytic activity of Co3Mo3N for electrochemical ammonia synthesis is lower than that of Pd. The successful synthesis of ammonia demonstrates that LiAlO2–(Li/Na/K)2CO3 composite exhibits protonic or/and oxygen ion conduction.
      PubDate: 2015-05-01
       
  • Infrared Reflection Absorption Spectroscopy of OH Adsorption on the Low
           Index Planes of Pt
    • Abstract: Abstract The adsorption of hydroxide (OHad) on Pt has been studied on the low index planes of Pt using infrared reflection absorption spectroscopy (IRAS) in electrochemical environments. We discuss the correlation between the integrated band intensity of the bending mode of OH of Pt–OH (δ PtOH) and the charge density of the oxide formation of Pt. The band of δ PtOH is observed around 1100 cm−1, and the onset potential depends on the surface structure. The onset potential of δ PtOH on Pt(110) and Pt(100) overlaps with the hydrogen adsorption/desorption potential region. The order of the integrated band intensity of δ PtOH at 0.9 V vs RHE is opposite to the order of the oxygen reduction reaction (ORR) activity. This finding supports that the OHad is one of the species deactivating the ORR.
      PubDate: 2015-05-01
       
  • Combinatorial Synthesis of Gold-Based Thin Films for Improved
           Electrocatalytic Conversion of CO 2 to CO
    • Abstract: Abstract Carbon dioxide electroreduction (CO2ER) was studied on 35 gold-based thin film catalysts sputtered on glassy carbon disks. A sputter-down setup was used for the deposition of these thin films in a combinatorial manner. Zinc and silver were employed in combination with gold in order to obtain new catalysts. Linear sweep voltammetry was employed to obtain the selectivity profile of each catalyst. Among the 35 catalysts, three ternary combinations (Au14Ag34Zn52, Au32Ag51Zn17, and Au16Ag10Zn74) and one binary combination (Au80Zn20) were identified as being active catalysts, reducing the dissolved CO2 in favor of proton reduction. Two ternary catalysts (Au16Ag10Zn74 and Au32Ag51Zn17) exhibited higher selectivity and lower overpotential for CO2ER than the pure metals. The Au80Zn20 binary catalyst exhibited the longest potential range where the selectivity for CO2ER remains constant. A decrease of the gold loading between 18 and 88 % was obtained for these catalysts, suggesting that they are promising candidates for an industrial application of CO2ER. Electrochemical impedance spectroscopy proved that the mechanism of CO2ER, involving two successive one-electron transfers, is identical on pure metals and combined sputtered catalysts.
      PubDate: 2015-05-01
       
  • 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
       
  • Effect of Platinum Nanoparticle Loading on Oxygen Reduction at a Pt
           Nanocluster-Activated Microporous–Mesoporous Carbon Support
    • Abstract: Abstract Very high surface area carbon-supported Pt nanoparticle catalysts have been applied to the oxygen reduction reaction in alkaline solution. The distribution effect of deposited Pt nanoparticles onto the carbon support on the oxygen reduction reaction kinetics has been established by comparing the various carbon-supported Pt (20 and 60 wt% metal) catalysts. The various Pt catalysts were prepared by using a sodium borohydride reduction method. All the catalysts showed a face-centered cubic crystal structure as determined by X-ray diffraction method; the average platinum particle sizes were ∼4.2, ∼4.8, ∼5.4, and ∼27.2 nm for 20 wt% Pt–C(Mo2C), 60 wt% Pt–C(Mo2C)-I, 60 wt% Pt–Vulcan XC72, and 60 wt% Pt–C(Mo2C)-II catalysts, respectively. The X-ray photoelectron spectra for all the catalysts indicated that most of the platinum nanoparticles have an oxidation state of 0. The low-temperature N2 sorption, time-of-flight mass spectrometry, scanning electron microscopy, and transmission electron microscopy experiments have been carried out to characterize the structure of prepared materials. The cyclic voltammetry and rotating disk electrode techniques were used to study the oxygen electroreduction kinetics.
      PubDate: 2015-05-01
       
  • The Effect of the Voltage Scan Rate on the Determination of the Oxygen
           Reduction Activity of Pt/C Fuel Cell Catalyst
    • PubDate: 2015-04-19
       
  • 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
       
  • Combinatorial Plasma Sputtering of Pt x Pd y Thin Film Electrocatalysts
           for Aqueous SO 2 Electro-oxidation
    • Abstract: Abstract A combinatorial sputtering system, based on magnetron enhanced plasma sputtering, was employed in the syntheses of PtxPdy thin film catalysts, and a multi-channel potentiostat allowed for high-throughput parallel screening of the deposited electrocatalysts towards the electro-oxidation of aqueous sulphur dioxide (SO2). Employing onset potential as the screening criterion, it was found that three PtxPdy bimetallic combinations exhibited satisfactory performance with the best compositions being that of Pt3Pd2 and PtPd4. Both these combinations exhibited the same lower onset potential of 0.587 ± 0.004 V, SHE compared to that of pure Pt (0.598 ± 0.011 V, SHE), and in addition contain less Pt in achieving these onset potentials.
      PubDate: 2015-04-08
       
  • 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: 2015-04-08
       
  • 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: 2015-04-07
       
  • 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: 2015-03-27
       
  • On the Temperature Performance of Ethanol Oxidation Reaction at
           Palladium-Activated Nickel Foam
    • Abstract: Abstract The present paper reports on ethanol oxidation reaction (EOR) investigated at catalytically modified nickel foam material. The EOR was studied in 0.1 M NaOH supporting electrolyte on Pd-activated nickel foam catalyst material, obtained by a spontaneous deposition method. Catalytic modification of Ni foam resulted in a composite material having superior EOR kinetics, as elucidated through corresponding values of a.c. impedance-derived charge-transfer resistance parameter (including temperature-dependence of the EOR over the temperature range 20–60 °C). The presence of a catalytic additive was disclosed from SEM and XRD analyses.
      PubDate: 2015-03-01
       
 
 
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