Pulsating overpotential

Pulsating overpotential consists of a periodic repetition of overpotential pulses of different shapes. Square-wave PO is defined in the same way as PC except that the overpotential pulsates between the amplitude value and zero instead of current density. Non-rectangular pulsating overpotential is defined by the amplitude of the overpotential, rj, frequency, and overpotential waveform [7]. 

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An experimental study of zinc electrodeposition on copper wire from 0.1 M zincate solution in 1.0 M KOH was presented by Simicic et al. [232]. A possible mechanism of the formation of spongy zinc deposits was considered. Also, it was shown that in the case of a square-wave pulsating overpotential regime, the deposit was less... 

Enhancement of the activity of Ag has been observed upon continuous potential cycling [265], as well as with more complex potential sequences including potential holding at some cathodic values [266] and pulsating overpotential [267]. The enhancement cannot be explained only in terms of surface area increase, so that the creation of especially active Ag sites has been postulated [266]. 

The formation of the smaller (and less different to each other) dendrites could be obtained by the increase of deposition overpotential. Unfortunately, the increased overpotential produces the hydrogen evolution in this system and the formation of degenerate dendrites and honeycomb-like deposits.76,77 Nevertheless, the dendritic growth in this system at larger overpotentials is possible by the application of appropriate square-wave pulsating overpotential (PO) regime. For example, the well-developed dendrites were formed with amplitude overpotential of 1,000 mV, deposition pulse of 10 ms, and pause of 100 ms (the pause to pulse ratio 10) (Fig. 26a). They can be well approximated by the cones shown in Fig. 23. Also, superficial holes due to attached hydrogen bubbles were formed between these dendrites, as can be seen from ref.78... 

Figure 26. (a) The copper dendrites formed by the pulsating overpotential (PO) regime deposition pulse of 10 ms, pause duration of 100 ms deposition time 18 min (b) The precursor of copper dendrite obtained by PO regime deposition pulse of 1 ms, pause duration of 10 ms deposition time 24 min. In both cases amplitude overpotential used was 1,000 mV. Reprinted from ref. 8 with permission of Elsevier. 

Popov Kl, Pavlovic MG, Pavlovic LjJ, Cekerevac MI, Removic GZ (1988) Electrode surface coarsening in pulsating overpotential copper electrodeposition. Surf Coat Technol 34 355-363... 

Popov KI, Stojiikovic ER, Radmiiovic V, Pavlovic MG (1997) Morphology of lead dendrites electrodeposited by square-wave pulsating overpotential. Powder Technol 93 55-61... 

Popov KI, Pavlovic MG, Jovicevic JN (1989) Morphology of tin powder particles obtained in electrodepositirm on coppr cathode by constant and square — wave pulsating overpotential from Sn(n) alkaline solutirm. Hydrometallurgy 23 127—137... 

Assuming that at sufficiently high frequencies the surface concentration in the pulsating overpotential deposition does not vaiy with time, it is easy to show that response of the current density, i, to the input overpotential ... 

However, an increase in surface coarseness in a deposition using a rectangular pulsating overpotential or pulsating current is only possible during the pulses of current or overpotential [35] and the integral form of Eq. (4.76) can be written as ... 

Fig. 4.8 Copper deposits obtained from 0.10 M CUSO4 in 0.50 M H2SO4 on a Cu wire electrode with a quantity of electricity of 20 mA h cm in (a) the constant potentiostatic regime an overpotential 210 mV initial current density 6.5 mA cm , as well as by the different pulsating overpotential (PO) regimes (b) initial average current density 6.5 mA cm = 322 mV pulse-...

Popov KI, Maksimovic MD, Zecevic SK, Stojic MR (1986) Surface roughening and dendritic growth in pulsating overpotential copper electrodeposition. Surf Coat Technol 27 117-129... 

Pavlovic MG, Maksimovic MD, Popov KI, Krsul MB (1978) The effect of pulsating overpotential on the morphology of electrodeposited silver powder particles. J Appl Electrochem 8 61-65... 

Popov KI, Maksimovic MD, Pavlovic MG, Ostojic GR (1977) Formation of powdered copper deposits by square-wave pulsating overpotential. J Appl Electrochem 7 331-337... 

Popov KI, Pavlovic MG, Stojilkovic ER, Radmilovic V (1996) Silver powder electrodeposition by constant and pulsating overpotential. J Serb Chem Soc 61 47-55... 

Fig. 5.8 (a, b) The pyramid-like and (c, d) dendritic structures of Cu obtained by the pulsating overpotential (PO) regimes with the same pause-to-pulse ratio 10, but with the different durations of deposition pulse (4) and pause (tp) (a, b) t = ms and tp = 10 ms, (c, d) = 10 ms and tp= 100 ms (Reprinted from Refs. [49, 50] with permission from Elsevier and Refs. [5, 23, 51] with kind permission from Springer)... 

Nikolic ND, Brankovic G, Pavlovic MG, Popov KI (2009) The effects of the pause to pulse ratio in the regime of pulsating overpotential on the formation of honeycomb-like structures. Electrochem Commun 11 421-424... 

Nikolic ND, Brankovic G, Maksimovic VM, Pavlovic MG, Popov KI (2010) Application of pulsating overpotential regime on the formation of copper deposits in the range of hydrogen co-deposition. J Solid State Electrochem 14 331—338... 

Powder particles with different grain size and morphology can be obtained by varying the wave of periodically changing current or overpotential [6]. In the dependence of the shape of square-wave pulsating overpotential (PO), it can be obtained either dendritic (Fig. 6.7a) or cauliflower-like (Fig. 6.7b) Cu particles... 

Effect of Regime of Pulsating Overpotential on the Shape of Silver Powder Particles... 

Typical deposits obtained by square-wave pulsating overpotential (PO) are shown in Figs. 2.8-2.10. It can be noticed by the analysis of these figures the decrease of both agglomeration and dendritic character of powder particles with the increasing off period and decreasing overpotential amplitude. 

This effect was quantitatively discussed for the regime of the square-wave pulsating overpotential [23, 31]. 

Fig. 2.8 Silver powder particles obtained by square-wave pulsating overpotential. Overpotential amplitude 300 mV. Pulse duration 5 ms. (a) Pause to pulse ratio 1, xlOO (b) pause to pulse ratio 1, xlOOO (c) pause to pulse ratio 3, x 100 and (d) pause to pulse ratio 3, x 1000 (Reprinted from [23] with permission from the Serbian Chemical Society.)...

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