Electrochemical and Spectroelectrochemical Properties of SnO2 and SnO2 / Mo Transparent Electrodes with High Ion‐Storage Capacity

Abstract

Thin solid and (10%, 2:1 and 1:1) films with an ion‐storage capacity of 20 to 30 mC/cm2 and weakly expressed cathodic electrochromism were deposited using the dip‐coating technique. The films were deposited from peroxo sols prepared by reacting and a metallic molybdenum precursor with . Thermogravimetric, surface area [Brunauer, Emmett, and Teller (BET)], x‐ray diffraction, and IR spectroscopic measurements of films heat‐treated at 500°C (5 min) revealed a nanocrystalline (grain size ∼30 Å) cassiterite structure with a large surface area (∼60 to 70 m2/g). The electrochemical properties of the films were studied in a 1 M /propylene carbonate electrolyte using cyclic voltammetry (CV) at different scanning rates (0.1 to 200 mV/s). Electrochromic properties, measured in situ with ultraviolet‐visible measurements, revealed that the coloring/bleaching changes accompanying insertion/extraction of ion processes are 10 to 15% for (1:1) films but decrease to a few percent with decreasing Mo content. Low‐scan‐rate CV measurements confirmed the presence of two different redox processes: and . This was confirmed from the ex situ IR spectroelectrochemical measurements of films charged/discharged to different extents. IR spectra of films heat‐treated at 500°C in a vacuum also showed that (2:1) films contain Brønsted acidic protons. These films, because of their low coloration efficiency (2 to 10 cm2/C), are promising counterelectrodes for electrochromic devices with light reflection modulation.