Hydrogen evolution cyclic voltammogram

For comparison we also show a cyclic voltammogram of a Au(lll) electrode (see Fig. 13.4). There is no detectable hydrogen adsorption region the hydrogen evolution reaction is kinetically hindered, and sets in with a measurable rate only at potentials well below the thermodynamic value. There is a much wider double-layer region in which other... 

Figure 13.4 Cyclic voltammogram of Au(lll) in 0.1 M HCIO4 on SCE scale. Note 0 V see = 0.2415 V SHE. The arrows indicate the equilibrium potentials for hydrogen and oxygen evolution reproduced by courtesy of D. Kolb, Ulm.

Fig. 15. Ru and RuOi-coated cathodes cyclic voltammogram of (a) RuO coating, (b) Ru-metal cathode, (c) semilogarithmic cnrrenl voltage curve of the cathodic hydrogen evolution at a Ru-coated and a RuO >-coated cathode in 30 wt% KOH at 80°C.

The cyclic voltammogram of Fig. 54a is not Hilly symmetrical. The distortion probably originates from the catalytic discharge of protons and evolution of hydrogen in the solid phase. These results suggest the possibility that by using cyclic voltammetry with a single crystal, the reduction potential of solid heteropoly compounds can be measured and that the effects of constituent elements described below can be made clearer. 

Fig. 3.8 Typical cyclic voltammogram of boron doped diamond film electrode. The result was tested in 0.5 M H2SO4 solution at 0.1 V s 1 scan rate. The standard hydrogen gas and oxygen gas evolution potentials were marked with E t and Eq2, respectively (after Guo and Chen 2007b)...

Figure 13.6.1 Cyclic voltammogram for a smooth platinum electrode in 0.5 M H2SO4. Peaks formation of adsorbed hydrogen. Peaks H oxidation of adsorbed hydrogen. Peaks Oq formation of adsorbed oxygen or a platinum oxide layer. Peak Oc reduction of the oxide layer. Point 1 start of bulk hydrogen evolution. Point 2 start of bulk oxygen evolution. The shape, number, and size of the peaks for adsorbed hydrogen depend on the crystal faces of platinum exposed (62), pretreatment of electrode, solution impurities, and supporting electrolyte. See also Figure 13.4.4.

It was established that the formation of free tin phase followed by strong inhibitive adsorption is possible in this region. It is reasonable that this feature is absent in Sn(II)-free solutions. The minimum under discussion develops gradually on addition of small amounts of Sn(II), and its depth may be used as a measure of Sn(II) concentration in the presence of Sn(IV) [105]. Besides, anodic currents of Sn dissolution are observed in cyclic voltammograms at > —0.24 V, when the reverse potential scan is applied (see below). An increase in current density arising at higher cathodic polarizations E < -0.4 V) is concomitant with hydrogen evolution. 

---