Fronts and stationary domains during electrochemical H2 oxidation on Pt: The impact of the position of the reference electrode on the spatiotemporal behaviour

Abstract

We studied the local potential distribution in front of a rotating Pt ring-electrode during hydrogen oxidation in sulfuric acid for three different positions of the reference electrode. The potential distribution was measured with a potential micro-probe. The experiments were carried out in the bistable region of the system. For large and medium distances between the reference (RE) and the working electrode (WE), transitions between the two homogeneous states occurred through nucleation and growth of the globally stable state from the initially metastable one. The transition time was considerably longer for the intermediate distance between the RE and the WE. For the closest distance used, stationary patterns formed, consisting of two domains with high and low current densities, respectively. The difference in the double layer potential of the two domains amounted to more than 1 V. The low-current density domain was covered with Pt-O whereas in the high current density domain the electrode surface consisted of 'bare' Pt. The existence of these stationary non-equilibrium structures as well as the difference of the front behaviour for the other two electrode arrangements can be traced back to the existence of a negative global coupling for intermediate and close distances between the WE and the RE

Experimental and Model Spatiotemporal and Spatial Patterns in Electrochemical Systems

“…I), in this section we shall discuss the formation of spatiotemporal patterns in this process, as described by Krischer, Varela et al in a series of papers [37][38][39][40][41]. In most experiments the specially designed setup was used, which included the ring Pt electrode as the working electrode, at which electrooxidation of H 2 occurred, while the series of microprobes located along this ring allowed to measure the actual spatial distribution of the electric potential (Fig.…”

“…[37]. In the presence of poisoning, electrosorbing ions (i.e., after addition of 0.1 mM HCl and 0.025 M CuSO 4 to the 0.5 mM H 2 SO 4 solution saturated with H 2 ), and under potentiostatic conditions, the system's dynamics was studied again for the three positions of the RE with respect to WE, corresponding to zero, intermediate, and maximum global coupling.…”

Trapping Electrochemical Oscillations between Self‐Organized Potential Walls

“…Conspicuous is that the NDR branch exhibits a shoulder (region 1 in curve i). This shoulder is due to spatial domains that develop owing to the NGC 10. The domains are stationary when fixing the voltage in the range of the shoulder.…”

“…The domains are stationary when fixing the voltage in the range of the shoulder. A typical position time plot is depicted in Figure 1 b 10. The data were obtained using a thin ring electrode, and hence the spatial coordinate here as well as in all other spatio‐temporal plots presents the angular variable along the ring electrode.…”

“…Compensated resistance (by means of a negative impedance device) in curve ii: 350 Ω. b) Example of stationary potential domains which typically develop when fixing the voltage in region 1 (curve i) (see ref. 10 ). c) Example of a travelling pulse which is typically found at a constant value of U in region 2 (curve ii) (see ref.…”