Fig. 3: Design optimization of a gauge-like EC module.
a Optical and SEM images (inset) of paste-type EC layer. b Cyclic voltammograms of paste-type EC layer (blue) and thin-film EC layer (red) in 1 M NaClO4 in propylene carbonate (PC) (scan rate: 50 mV s−1). c Schematic illustration of gauge-like EC layer structure and the mechanism of EC reaction propagation. The upper panel shows the overall architecture, in which the EC layer, composed of WO3 nanoparticles (NPs)/UV-treated carbon (UV-CB)/ xanthan gum (XG), is positioned laterally adjacent to the W current collector. Electrons initially flow along the W current collector, initiating the EC reaction first at the region near the W current collector. The lower panel shows a magnified view of the propagating EC front within the gauge-like EC layer. As the WO3 NPs undergo EC reaction, their electrical conductivity increases, enabling electron transfer to neighboring unreacted WO3 NPs. Simultaneously, Na+ ions intercalate, driven by the electrical field between the EC layer and the counter electrode, supporting lateral propagation of the EC reaction across the layer. d EC reaction propagation images of the gauge-like EC layer under an applied potential of –1.6 V versus the Prussian Blue (PB) counter electrode. Images were captured at 20 min intervals over 1 h. e Amperometric profiles of the gauge-like EC layer (blue) and a layered EC layer (red) measured 1 mm-thick CA-PMDA organogel electrolyte containing 1 M NaClO4 in PC, under an applied potential of −1.6 V versus the Prussian Blue (PB) counter electrode. f Cumulative reaction charge (blue) and corresponding EC propagation distance (red) of the gauge-like EC layer under an applied potential of −1.6 V. g Correlation between cumulative reaction charge and EC propagation distance of the gauge-like EC layer under applied potentials of −1.6 V (red) and −1.4 V (blue).
