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Articles by Zekerya DURSUN
Total Records ( 5 ) for Zekerya DURSUN
  Zekerya DURSUN , Sami BEN AOUN and Isao TANIGUCHI
  Au(111) single crystal electrodes were modified by underpotential deposition (UPD) of Cd ad-atoms with different coverages, which were used for the electrocatalytic oxidation of glucose in alkaline media. The catalytic activity of the electrodes was dependent on how the Cd ad-atoms covered the surface. Under the presented experimental conditions the monolayer (ML) Cd ad-atom-covered Au(111) electrode had the best catalytic activity on D-glucose oxidation, in terms of both potential shifts and peak current increases, as compared to the 0.11, 0.5, and 2 ML covered and bare Au(111) electrodes. Double layer capacity measurements revealed that the shifts of the potential of zero charge (pzc) were dependent on the different surface coverages of the Cd ad-atom-modified Au(111) electrodes, which is in good agreement with cyclic voltammetric results, as the current flow was initiated for glucose oxidation after a slightly more positive potential of pzc in all Cd ad-atom-modified Au(111) and bare Au(111) electrodes.
  Zekerya DURSUN , Levent PELIT and Isao TANIGUCHI
  A single-crystal Au(111) electrode was used for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) in a phosphate buffer solution at pH 6.9. The single-crystal Au(111) electrode displayed excellent electrocatalytic activity for DA and AA oxidation in comparison to a Au disk electrode. Although the anodic peaks of both reagents overlapped on the Au disk electrode, the anodic peak potentials of DA and AA in their mixture were well separated since the peak potential of AA was shifted to more negative values by cyclic and differential pulse voltammetry. The oxidation peak current increased linearly with the concentration of DA in the range of 5 x 10-6-5 x 10-4 mol/L in the presence of 5 x 10-4 mol/L AA. The detection limit of DA was 5 x 10-7 mol/L. The peak current also linearly increased with increasing AA concentration in the presence of 5 x 10-4 mol/L DA in the range of 1 x 10-6-5 x 10-4 mol/L. The detection limit of AA was 5 x 10-8 mol/L (s/n = 3). The single-crystal Au(111) electrode showed excellent electrocatalytic activity to both AA and DA, probably because hydrogen flame treatment made the single-crystal electrode surface a well-defined atomic structure.
  Zekerya DURSUN , Sukriye ULUBAY KARABİBEROGLU , Buket GELMEZ and Fatma Nil ERTAS
  Electrocatalytic reduction of oxygen at electrochemically deposited Pt ad-layer modified Au(111) electrodes was studied in an O2-saturated NaOH (0.1 M) solution. The results were compared with those obtained by using a polycrystalline Pt electrode and another Pt-deposited electrode prepared by replacement with Cu on bare Au(111). Linear sweep voltammetry displayed a positive shift of the oxygen reduction potential by about 0.14 V compared to the bare Au(111) electrode. This shift was about 0.06 V compared to a Pt disk electrode. Tafel slopes gradually changed between 0.06 and 0.1 V/dec, from 0.075 to -0.10 V/dec, from lower to higher current density region. The Pt ad-layer clearly served as a catalyst for oxygen reduction via 4-electron transfer. In terms of the desired shift in reduction potential and increased current density, the best electrocatalytic activity was obtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.
  Ethanol oxidation was studied on single-crystal Au(111) electrodes that were modified by platinum, palladium, and cadmium metal ad-layers. The metal ad-layer modification was carried out by the underpotential deposition process, in which controlled amounts of Pt, Pd, and Cd were electrodeposited onto the substrate as submonolayer or monolayer coverage. The activity of the metal ad-layer modified Au(111) electrodes toward ethanol oxidation was studied in alkaline media, and recorded voltammograms were compared to those of bare single crystal Au(111) and polycrystalline gold and platinum disk electrodes. In terms of the desired shift in reduction potential and increased current density, the best electrocatalytic activity was obtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.
  Suleyman KOCAK , Zekerya DURSUN and Fatma Nil ERTAS
  The electrochemical oxidation of methanol was investigated by using various ad-layer modified Au(111) electrodes in alkaline media in comparison to Au(111), polycrystalline Pd, and polycrystalline Pt electrodes. Catalytic activity of gold toward methanol oxidation has tended to increase in more alkaline media, as reflected in the oxidation peak in the concentration range of NaOH (0.1-3.0 M) studied here. The oxidation peak potential of methanol shifted to more negative potentials, indicating a pH-dependent surface reaction. Among the electrodes studied, single-crystal gold electrode surfaces modified with Pd and Pt ad-layers displayed the highest catalytic activity for methanol oxidation. Additional shifts of about 350 mV in the oxidation peak potential of methanol was observed for both ad-layer modified electrodes to more negative potentials compared to that of bare electrodes. The Pd and Pt ad-layer modified Au(111) electrode surfaces did not only supply a superior electrical contact, but also accelerated electron transfer, as shown by the increase in peak current and the positive shift in peak potential. This effect was supported by the doublelayer capacitance measurements of bare Au(111) and Pd ad-layer modified singlecrystal electrodes where the potential of zero charge changed from 15 to 5 mV.
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