Sulfur cyclic voltammogram

Figure 17.14 Cyclic voltammograms recorded at 1 V s at a PGE RDE rotating at 2500 rev min ) modified by adsorption of a submonolayer film of [NiEe]-hydrogenase from the purple photosynthetic sulfur bacterium Allochromatium vinosum in buffered aqueous solution at pH 7.0 under an atmosphere of H2 (1 bar). Reprinted with permission from Leger et al., 2002. Copyright (2002) American Chemical Society.

Figures 2-15 shows the cyclic voltammogram of Pt(lll) in 0.5 M sulfuric acid. The potential was first cycled between 60 mV and 700 mV and later was scanned up to 1500 mV and reversed.

The cyclic voltammogram of PtdlO) in 0.5 M sulfuric add is shown in Fig. 2-16. Hs drogen adsorption-desorption current consisted of a lax e peak at 150 mV and a shoulder at 200 mV. The oxidation begins at 800 mV. Unlike PtClll), the shape of the voltammogram in the hydrogen region did not change much after the reconstruction of the surface by a sweep to an anodic potential of 1550 mV. 

The cyclic voltammograms for Pt(llO) and Pt(lOO) in 0.5 M perchloric acid are shown in Fig. 2-26 and Fig. 2—27 respectively. The shapes of the voltammograms for hydrogen adsorption-desorption were significantly different from those in sulfuric add. Although these anion... 

Figure 2-31 showed the cyclic voltammogram of the platinum electrode partially covered with COad in 0.5 M sulfuric acid. The potential was held at -(-400 mV during the CO adsorbing period (10 s, 100 CO bubbled) and the COad removing period (10 min., 100% N2 bubbled). After that, the potential was swept in the cathodic direction to +50 mV first and then in the anodic direction to 1500 mV to take the voltammogram. 

Figures 2-39 are the cyclic voltammograms for a platinum electrode fully covered with COad 0.1 M perchloric add. Like in a dilute sulfuric add, the oxidation peak of COad shifted to a more negative potential by choosing a slower scan rate.

Methanol oxidation activities have been examined on a Pt-Sn electrode. Cyclic voltammograms of a smooth Pt-Sn electrode in 3 M sulfuric acid with 1 M methanol are shown and compared with pure platinum in Fig. 4-17. 

In 1992 the cyclic voltammogram feature of Pt single crystals in sulfuric acid solution was examined by CO adsorption. Figure 13 shows the effect of CO adsorption on Pt(lll) in sulfuric acid solution, " where at ads=0-08,0.3, and 05 V(RHE), CO gas was introduced and the current... 

Sulfate adsorption on Pt(lll) was investigated by thermodynamic treatment of the Gibbs excess, which is based on the Frumkin treatment.The above cyclic voltammogram feature at Pt(lll) in sulfuric acid solution was also thought to be due to the adsorbed sulfate. ... 

Figure 18. Cyclic voltammograms on Au(III) in sulfuric acid solution. (A) In O.SmAf H2SO4 at lOmAf s", (B) in 50mM H2SO4 + O.lmAf Ag at 2mA/ s, and (C) in 0.5mA/ H2SO4 + 0.1 itiA/ Ag at 2 mV s. The dotted curve of (C) represents a cyclic voltam-mogram in the gold oxidation region. (From Ref. 19.)...

Underpotential deposition of Zn on R was seen as adsorption of Zvi ions in 1970, since is as high as 1V, a value that well exceeds the one expected from previous results on various metal combinations of underpotential deposition systems. Recently, Zn underpotential deposition on R was reported in acidic solutions, and then in alkaline solutions. Zn underpotential deposition on Pd was also found in acidic and alkaline solutions. Then cyclic voltammograms of underpotential deposition on three low-index, single-crystal Rs were observed in sulfuric and perchloric acid solutions, as shown in Figs. 27 and 28. " In comparing Figs. 27 and 28, Zn underpotential deposition on R seans to take place only on Pt(llO), but not on Pt(lll) and Pt(lOO). Therefore it can be said that a cyclic voltammogram on polycrystalline R was observed on a R(110)-like surface. 

A cyclic voltammogram ofZn underpotential deposition on Pt(llO) in sulfuric acid solution is more reversible than that in perchlorie acid solution with respect to the change of potentials, as shown in Fig. 27. The was evaluated as about 1 V. Since Zn underpotential deposition in acidic solutions was observed in the adsorbed hydrogen region, the pH was increased to separate Zn underpotential deposition from the hydrogen adsorption region. At pH 4.6, Zn underpotential deposition was observed, as shown in Fig. 29. The different cyclic voltammogram appearances of Zn underpotential deposition on Pt(lll) at different pHs is discussed in Section n.4. 

Cyclic voltammograms of PtSn microelectrodes in 0.5 M sulfuric acid solution are shown in Fig. 15.6. The potential range was -200 to 800 mV (vs. SCE) and the scan rate was 100 mV/s. It can be seen clearly that hydrogen desorption from the PtSn-2 electrode is seriously inhibited compared with that from the PtSn-1 electrode. From the hydrogen desorption peak areas in the CV curves and the Pt single crystallite hydrogen desorption constant of 210 /xC/cm Pt, the electrochemical surface areas (ESA) for PtSn-1 and PtSn-2 were calculated to be 391 and 49 cm /mg, respectively. However, it is evident from XRD and TEM results that the two catalysts have similar particle size and so they should possess the similar physical surface area. The difference... 

Fig. 1 Cyclic voltammogram of Au(l 11) electrode in 0.10 M sulfuric acid containing 1.0 mM Hg + scan rate 2 mV s. Inset voltammetric profile over the potential range +1.05 to +0.70 V versus Ag/AgCl (3 M KCl) (from Ref 23).

Herrero and Abruna [25] have also studied the kinetics and mechanism of Hg UPD on Au(lll) electrodes in the presence and absence of bisulfate, chloride, and acetate ions. In the absence of the interacting anions (in perchloric acid), the Hg UPD was significantly controlled by gold-mercury surface interactions. In sulfuric acid solutions, the kinetics of the initial and final stages of mercury deposi-tion/dissolution was altered. The presence of two well-ordered structures at potentials below and above mercury deposition led to the formation of two pairs of sharp spikes in cyclic voltammograms. In the chloride medium, the voltammetric profile exhibited two sharp peaks and thus it was very similar to that obtained in sulfuric acid solution. Neither nucleation, nor growth kinetics mechanism was found to be linked to the process of formation/disruption of the mercury chloride adlayer. The transients obviously deviated from the ideal Langmuir behavior. 

Grauel and Krischer also detected similar stationary domains during the oxidation of H2 on a Pt ring electrode in sulfuric acid [182]. As can be seen in the cyclic voltammogram in Fig. 46a, in this case the homogeneous active branch coexisted with the oxide covered passive branch, and thus the homogeneous dynamics were bistable. The stationary structure displayed in Fig. 46b spontaneously formed when a... 

The [p,-S2 Fe (S4) 2] complex forms from FeCl2, S -, and elemental sulfur in boiling THF (122). It shows a different structure, but exhibits similar electronic spectra and cyclic voltammograms as [ r-S2 Ru(PPh3)(S4) 2l-... 

Figure 48. UV-Vis spectro-cyclic voltammogram corresponding to the first CV cycle for the oxidation of aniline (50 mM) in aqueous sulfuric acid (0.5 M) at v = 0.2Vs . The inserts show the voltammogram and the potential dependence of the absorbance. (From Ref. 335.)...

The electrochemical activation was carried out in successive reduction and oxidation in 1 M sulfuric acid. The corresponding potentials were -t-2.40 V (oxidation) and -0.35 V (reduction) vs. reference (Ag/AgCl). After each step 10 cyclic voltammograms were recorded followed by an impedance measurement. Both methods were initiated by an open circuit measurement for 1200 s. 

Figure 27.Cyclic voltammograms of Ni-powder modified CCE in 0.1 M NaOH Solution at scan rate lOOmVs 1. The cycle numbers are written on the voltammograms. Reprinted from Electrochimica Acta, 51 A. Salimi, M. Roushani, R. Hallaj, Micromolar determination of sulfur oxoanions and sulfide ata renewable sol-gel carbon ceramic electrode modified with nickel powder, 1954, Copyrights(2006) with permission from Elsevier.

FIGURE 11.1 Cyclic voltammograms (dashed lines) run from 0.05 to 0.80 V at 0.050 V s-1 of (a) spontaneously deposited ruthenium suhmonolayer on clean Pt(lll) (solid lines) from 120 s. 0.5 mM Ru(IH) CI3 solution in 0.1 M perchloric acid (h) spontaneously deposited osmium submonolayer on clean Pt(lll) (solid lines) from 60 s. 0.5 mM Os(III) solution in 0.2 M sulfuric acid. 

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