Surface-Enhanced Counter Electrode Materials for the Fabrication of Ultradurable Electrochromic Devices

Abstract

Electrochromic devices (ECDs) and especially electrochromic supercapacitors, where the real-time state of charge is indicated by the color, have a wide range of applications. However, to meet modern challenges, these devices should demonstrate exceptional charge–discharge durability. In this work, we demonstrate that electrochemical cycling stability of ECDs based on a monolayer of 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine–iron­(II) complex that was covalently linked to the working electrode (WE) can be drastically enhanced by a proper design of the counter electrode (CE). Enhancing the surface area of the flat indium tin oxide (ITO) CE by a layer of screen-printed ITO nanoparticles results in an ECD that upon continuous spectro-electrochemical switching for 600 cycles demonstrates negligible deterioration of the change in optical density. The enhanced surface area of the CE significantly diminishes the electrode and gel electrolyte degradation and allows us to gain fundamental insight into the pathway of degradation of the electrochromic molecules at the WE. During prolonged cycling (20,000 and 50,000 cycles), the overall total resistance of ECDs remains fairly unchanged, while the capacitance decreases due to a loss of the pseudocapacitive component associated with electrochromic molecules. X-ray photoelectron spectroscopy (XPS) suggests that this loss is likely due to the cleavage of the linkage C–N+ bond followed by the dissolution of the entire metal complex molecule into the electrolyte.

Nonconventional Symmetric Double-Side Electrochromic Devices Employing a Nafion Conductive Layer to Unlock Superior Durability

“…Previously, we have demonstrated that ECDs of the basic configuration (Figure 1A) often suffer from polarization of the CE leading to decomposition of the Li + gel electrolyte on the interface with CE. 25,26 Utilization of high surface area CE allows one to drastically slow down the rate of the decomposition of the solid-state EDCs during electrochemical cycling and, thus, provides access to ultradurable devices. 25,26 In this work, we examined and compared the long-term cycling durability performance of the double-side ECDs, ds-Fe4′T-S-ECD and ds-Nf-Fe4′T-S-ECD.…”

“…The enhanced cycling stability, in this case, comes from the higher surface area of the CE that allows better ion distribution upon the formation of a double layer and reduces cell polarization by compensating for the charge at the WE. 25,26 Sealing together two Fe4′T/ITO NPs ECMs the way that they face each other using the gel electrolyte gives a symmetrical device. Because Fe4′T/ITO NPs ECM is colored in its native state, the traditional symmetric device architecture does not show a significant change in optical density.…”

“…Nevertheless, the device showed superior electrochemical durability for over 50,000 cycles. 26 As a result, a symmetric device architecture may be ideal for the development of highly durable double-side ECDs if the color-bleed from identically colored CEs can be minimized. Taking this into account, we propose here a nonconventional symmetric ECD design that contains an ion conductive opaque spacer able to reflect the light back.…”

Elemental and molecular characterization of degrading blood pools

“…These values are typical for the ferrous (Fe 2+ ) oxidation state. 24 It should be mentioned that even though the C 1s spectrum of the fresh bulk sample contains the same features as the initial bloodstain, the ratio of the (C-C) : (C-O and C-N) : (CvO and OvC-N) is equal to 47.8 : 13.6 : 10.3. The increase of the aliphatic carbon content on the surface of the bulk compared to the surface of the initial bloodstain indicates a different Paper Analyst protein content.…”

Dual Redox-Responsive Os/Ru-Based Alternated Heterobimetallic Supramolecular Polymer as a Multicolor Electrochromic Material for Camouflage Devices

“…Electrochromic (EC) materials and electrochromic devices (ECDs) that show reversible color change upon application of a voltage have been widely used in a number of commercial and military applications, including energy-saving smart windows, − flexible displays, , e-papers, , protective eyewear, , security, , energy storage devices, − camouflage, − and so on. In the past few decades, various types of materials have been established as EC materials, which can be classified into inorganic EC materials (various transition-metal oxides), organic EC materials (organic small molecules and polymers), and organic–inorganic hybrid EC materials (various metal–organic systems). − Metallo-supramolecular polymers (MSPs) are generally considered as organic–inorganic hybrid EC materials because these polymers are typically synthesized by 1:1 complexation between organic ligands and metal ions. ,, Since Higuchi et al demonstrated the EC color change of MSP prepared from 1,4-bis­(2,2′:6′,2″-terpyridine-4′-yl)-benzene as a ditopic ligand and the Fe­(II) ion as the metal ion, many MSPs have been developed using bisterpyridine ligands and various metal ions like Fe 2+ , Co 2+ , Ru 2+ , Os 2+ , Cu 2+ , and so forth. ,− These monometallic MSPs have attracted great research attention for EC applications because of their interesting physical and optoelectronic properties like solution processability, high color contrast, fast response times, good coloration efficiency, and high durability.…”