Electrochemical Impedance Imaging on Conductive Surfaces

Abstract

Electrochemical impedance spectroscopy (EIS) is a powerful tool to measure and quantify the system impedance. However, EIS only provides an average result from the entire electrode surface. Here, we demonstrated a reflection impedance microscope (RIM) that allows us to image and quantify the localized impedance on conductive surfaces. The RIM is based on the sensitive dependence between the materials' optical properties, such as permittivity, and their local surface charge densities. The localized charge density variations introduced by the impedance measurements will lead to optical reflectivity changes on electrode surfaces. Our experiments demonstrated that reflectivity modulations are linearly proportional to the surface charge density on the electrode and the measurements show good agreement with the simple free electron gas model. The localized impedance distribution was successfully extracted from the reflectivity measurements together with the Randles equivalent circuit model. In addition, RIM is used to quantify the impedance on different conductive surfaces, such as indium tin oxide, gold film, and stainless steel electrodes. A polydimethylsiloxane-patterned electrode surface was used to demonstrate the impedance imaging capability of RIM. In the end, a single-cell impedance imaging was obtained by RIM.

Imaging solid–electrolyte interphase dynamics using operando reflection interference microscopy

“…On the other hand, the accumulation of charges on the electrode surface will change the permittivity of the metal electrode surface and accordingly induce a decrease in the reflected optical intensity. Such EDL-effects have been previously observed by RIM in our previous work 44,45 . Zhou et al also reported the EDL established at the solid/liquid interface when the Cu electrode was charged to 1 V 33 .…”

Visualization of working electrode reactivity from an electrochromic counter electrode

“…This is why we did not test higher voltage. However, the latter could be questionable as the optical properties of Au surface were reported to vary under applied potential [28]. Fig.…”

Optical mapping of the evolution of water content during the swelling of hydrophilic polymers

“…Recently, magnetic resonance imaging (MRI) has been employed to map the distribution of the water content within polymers, providing vivid information on the transport of water molecules in hydrogels. 18,19 In recent years, advanced optical imaging techniques have been rapidly developed to successfully image the physical and chemical properties of nanofilms, 20,21 single nanoparticles 22 and even single molecules due to their excellent sensitivity and high spatiotemporal resolution. 23 For example, Lu et al monitored the dynamic evolution of polymer-aging by specifically lighting up the aging products with a fluorescence microscope.…”