Charge-balanced waveforms

Asymmetric charge balanced waveforms in which the anodic pulse is delivered at a lower current but a longer pulse length compared to the cathodic one were found to allow higher values of anodic bias voltages, thus maximizing the iridium oxide charge injection capacity [28],... 

Fig. 16 Current and voltage waveforms of a PEDOT-coated Pt electrode under pulse stimulation (a). The electrode was stimulated in PBS under a charge-balanced, cathodic-first, biphasic pulse current at 1 mC/cm at 50 Hz (b). Voltage excursion was measured under pulse stimulation currents to evaluate the PEDOT electrode charge injection capacity...

It is stated in [3] that even completely symmetrical bi-phasic current waveforms would not result in charge balance and will cause a residual voltage and charge build-up on the electrodes. The reason is the presence of a faradaic resistor Rfw parallel to the electrode-electrolyte interface capacitor. This resistor models the electron transfer across the electrode-electrolyte surface. The resulting electrode model which is called Randles model is shown in Fig. 3.2. For example in [3], for sputtered iridium oxide electrodes with 400 p,m diameter in saline solution, Rp f = 17.12 kQ, Rs = 2.1 and Chw = 909nF were extracted using the step response of the electrode voltage to an input current. 

Fig. 11 Electrochemical Processes and Potential Waveforms During Chaise-Balanced Stimulation (a) capacitive charging only (b) reversible hydrogen plating (c) irreversible hydrogen evolution...

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