Determination of Surface Intrinsic Resilience against Bubble Coverage Using Localized Electrochemical Impedance Spectroscopy Time Domain Information

Abstract

Bubble coverage on electrode surfaces presents challenges for the wide application of water electrolysis technology. Earlier experimental studies on superaerophobic electrode surfaces indicated that surface roughness of microscale morphologies can greatly increase the surface’s resilience against bubble coverage at high current densities. Localized electrochemical impedance spectroscopy (LEIS) is used in this paper to assess this surface conductance under bubbles. The local impedance of the bubble-shielded area and the contour around the bubble were investigated on polished nickel and dynamic hydrogen bubble templating (DHBT) nickel surfaces with different porosities and pore distributions. This study demonstrated that porosity could reduce the resistivity caused by bubble coverage, and an evenly distributed porous surface is more resilient to bubble coverage.

Study on Bubble Dynamics in Photoelectrochemical Water Splitting with Low-Rate Flow Fields

“…Therefore, it is necessary to use various methods to avoid the prolonged attachment of bubbles and reduce their effect on efficiency. Wang et al 14 found that bubbles mainly caused the increase in impedance of the bilayer by using localized electrochemical impedance spectroscopy. Moreover, the use of electrodes with a large porosity and a uniform distribution of voids can effectively reduce the impedance of bubbles.…”

Revealing the Role of the Ionomer at the Triple-Phase Boundary in a Proton-Exchange Membrane Water Electrolyzer

“…At 2.5 V, the Ionomer-Ir electrode shows a current density (2278 mA cm –2 ) 23.2% lower than that of the pristine Ir electrode (2966 mA cm –2 ). Through measurement of the EIS at 1.7 and 2.0 V, the difference in the fitted first semicircles indicated that the ionomer coverage does not decrease but rather significantly enhances the charge transfer on the Ir surface (Figure b,c) . This indicates the substantial performance loss derived from the increased transport resistance due to the barrier effect of the ionomer.…”

“…In general, a larger bubble on the catalyst surface brings higher charge transfer resistance, 29,30 and in this kind of microelectrode system, it is embodied as a larger first semicircle. 25 However, although the ionomer significantly increases the size of the bubbles on the Ionomer-Ir surface, as the voltage increases, the existence of an ionomer significantly reduces the charge transfer resistance (Figure 2b,c). This suggests that the ionomer film may decouple the bubble evolution sites from the OER reaction sites and provides additional proton transport paths to the catalyst surface rather than limited transfer through the EDL on the bubble contour and the substrate surface (Figure 4a,b).…”

“…This suggests that the ionomer film may decouple the bubble evolution sites from the OER reaction sites and provides additional proton transport paths to the catalyst surface rather than limited transfer through the EDL on the bubble contour and the substrate surface (Figure 4a,b). 25 This allows the ionomer network to act as a buffer between the catalyst surface and bubbles, substantially weakening the effect of bubble coverage on ion transport through its internal ion transport routes. However, with lower charge transfer resistance, the Ionomer-Ir electrode still experiences greater potential fluctuations in the CP measurement due to bubble evolution (Figure 3b).…”

“…Through measurement of the EIS at 1.7 and 2.0 V, the difference in the fitted first semicircles indicated that the ionomer coverage does not decrease but rather significantly enhances the charge transfer on the Ir surface (Figure 2b,c). 25 This indicates the substantial performance loss derived from the increased transport resistance due to the barrier effect of the ionomer. The prolonged oxygen transport distance and oxygen barrier nature of the Nafion ionomer limit the rate of oxygen leaving the catalytic surface.…”