Ultrafast switching of an electrochromic device based on layered double hydroxide/Prussian blue multilayered films

Electrochromic-Induced Rechargeable Aqueous Batteries: An Integrated Multifunctional System for Cross-Domain Applications

Multifunctional electrochromic-induced rechargeable aqueous batteries (MERABs) integrate electrochromism and aqueous ion batteries into one platform, which is able to deliver the conversion and storage of photo-thermal-electrochemical sources. Aqueous ion batteries compensate for the drawbacks of slow kinetic reactions and unsatisfied storage capacities of electrochromic devices. On the other hand, electrochromic technology can enable dynamically regulation of solar light and heat radiation. However, MERABs still face several technical issues, including a trade-off between electrochromic and electrochemical performance, low conversion efficiency and poor service life. In this connection, novel device configuration and electrode materials, and an optimized compatibility need to be considered for multidisciplinary applications. In this review, the unique advantages, key challenges and advanced applications are elucidated in a timely and comprehensive manner. Firstly, the prerequisites for effective integration of the working mechanism and device configuration, as well as the choice of electrode materials are examined. Secondly, the latest advances in the applications of MERABs are discussed, including wearable, self-powered, integrated systems and multisystem conversion. Finally, perspectives on the current challenges and future development are outlined, highlighting the giant leap required from laboratory prototypes to large-scale production and eventual commercialization.

Novel Prussian White@MnO2-Based Inorganic Electrochromic Energy Storage Devices with Integrated Flexibility, Multicolor, and Long Life

Flexible electrochromic devices have attracted considerable attention in recent years due to their great potential in smart multifunction electrochromic energy storage devices and wearable intelligent electronics. Herein, we present an inorganic flexible Li-based electrochromic energy storage device (EESD) by combining a Prussian white@MnO₂-composited electrode (PWM) and sputtering-made WO₃ electrode. The synergistic effect of Prussian white and MnO₂ plays a positive role both in energy storage and electrochromic property of the EESD. Its energy level can be quantified by the transmittance spectrum and chrominance difference, and its charging-discharging process can be monitored in real time by optical modulation at special wavelength. Specifically, the EESD can endure a 10,000 times cyclic voltammetry cycle without obvious degradation at wide voltage windows (-2 to 2.5 V) and realize a high coloration efficiency (77.6 cm²/C) with 35% optical modulation at 510 nm. In terms of energy storage performance, the EESD demonstrates excellent volumetric energy/power density (1.25 W cm^-3/13.2 mWh cm^-3) and remarkable stability with close to 98.3% capacitance retention and 99.4% coulombic efficiency after more than 4000 cycles. Its charging and discharging degree can be visualized in different spectral regions. There are 40% transmittance change for charging in the blue light region (450-480 nm) and 45% transmittance change for discharging in the red light region (620-750 nm). Based on its multicolor property, a quantitative indicator of charge state is achieved by the linear dependence of real-time chrominance change as stored or released charge. The ∼11 mC/cm² stored charge capacity can cause an ∼11 increase in chrominance difference ΔE value, while ∼7 mC/cm² discharge capacity can cause a ΔE value increase of ∼4. This work provides an efficient strategy to develop portable multicolor-integrated EESDs toward high performance and long stability.

Emerging Electrochromic Materials and Devices for Future Displays

With the rapid development of optoelectronic fields, electrochromic (EC) materials and devices have received remarkable attention and have shown attractive potential for use in emerging wearable and portable electronics, electronic papers/billboards, see-through displays, and other new-generation displays, due to the advantages of low power consumption, easy viewing, flexibility, stretchability, etc. Despite continuous progress in related fields, determining how to make electrochromics truly meet the requirements of mature displays (e.g., ideal overall performance) has been a long-term problem. Therefore, the commercialization of relevant high-quality products is still in its infancy. In this review, we will focus on the progress in emerging EC materials and devices for potential displays, including two mainstream EC display prototypes (segmented displays and pixel displays) and their commercial applications. Among these topics, the related materials/devices, EC performance, construction approaches, and processing techniques are comprehensively disscussed and reviewed. We also outline the current barriers with possible solutions and discuss the future of this field.

Synthesis of two-Dimensional layered double hydroxide: A systematic overview

Two-dimensional (2D) layered double hydroxides (LDH) are classic materials in fundamental research and practical application. 2D LDH have unique structural features, such as high aspect ratio, high specific surface area,...

Boosting Transport Kinetics of Ions and Electrons Simultaneously by Ti3C2Tx (MXene) Addition for Enhanced Electrochromic Performance

Electrochromic technology plays a significant role in energy conservation, while its performance is greatly limited by the transport behavior of ions and electrons. Hence, an electrochromic system with overall excellent performances still need to be explored. Initially motivated by the high ionic and electronic conductivity of transition metal carbide or nitride (MXene), we design a feasible procedure to synthesize the MXene/WO_3-x composite electrochromic film. The consequently boosted electrochromic performances prove that the addition of MXene is an effective strategy for simultaneously enhancing electrons and ions transport behavior in electrochromic layer. The MXene/WO_3-x electrochromic device exhibits enhanced transmittance modulation and coloration efficiency (60.4%, 69.1 cm² C^-1), higher diffusion coefficient of Li⁺ and excellent cycling stability (200 cycles) over the pure WO_3-x device. Meanwhile, numerical stimulation theoretically explores the mechanism and kinetics of the lithium ion diffusion, and proves the spatial and time distributions of higher Li⁺ concentration in MXene/WO_3-x composite electrochromic layer. Both experiments and theoretical data reveal that the addition of MXene is effective to promote the transport kinetics of ions and electrons simultaneously and thus realizing a high-performance electrochromic device. This work opens new avenues for electrochromic materials design and deepens the study of kinetics mechanism of ion diffusion in electrochromic devices.

Optical Sensing with a Potentiometric Sensing Array by Prussian Blue Film Integrated Closed Bipolar Electrodes

The simultaneous optical readout of a potentiometric sensor array of ion-selective electrodes (ISEs) based on PVC membranes is described here for the first time. The optical array consists of electrochromic Prussian Blue (PB) films in multiple closed ion-selective bipolar electrodes (BPEs), which gives a physical separation between the optical detection and sample compartments. The potential-dependent turnover of PB generates Prussian White (PW). A near-Nernstian response of the PB film is confirmed by colorimetric absorbance experiments as a function of applied potential. In the combined bipolar electrode cell, the overall potential is kept constant with a single potentiostat over the entire array where each PB spot indicates the potential change of an individual connected potentiometric probe. For cation-selective electrodes, the absorbance or blue intensity of the connected PB film is enhanced with increasing target cation activity. The colorimetric absorbance changes are simultaneously followed by a digital camera and analyzed by Mathematica software. A multiple cation-BPE array allows one to achieve simultaneous quantitative analysis of potassium, sodium, and calcium ions, demonstrated here in highly colored fruit juices. Mass transport at the PB thin film is shown not to be rate-limiting. The measuring ranges can be tuned in a wide range by potential control. The PB film exhibits greatly improved reproducibility and stability as compared to previous work with a ferroin redox probe confined in a thin solution layer.

A fast-switching electrochromic device with a surface-confined 3D metallo-organic coordination assembly

Demonstrated herein is a fast (<1 s)-switching solid-state electrochromic device (t = 0.49 s for coloration and 0.90 s for bleaching), fabricated with a novel imidazolium-linked [Fe(terpyridine)2]2+ chromophore-based surface-confined three dimensional metallo-organic coordination assembly. The device also exhibits promising electrochromic attributes such as high coloration efficiency (η = 275 cm2 C-1), moderate operating voltage (from -2 V to +3.2 V) and transmittance contrast (ΔT = 40%), and high cycling stability (up to 4500 cycles).

Self-Limiting Assembly Approaches for Nanoadditive Manufacturing of Electronic Thin Films and Devices

Most electronics consist of functional thin films with tens of nanometer thicknesses. It is usually challenging to control the growth of these thin films using conventional solution-based approaches. Nanoadditive manufacturing, a method to deposit electronically desired molecules, polymers, or nanomaterials in a layer-by-layer (LbL) fashion, has emerged as a promising technique for the precise control of film growth and device fabrication. Here, basic principles of nanoadditive manufacturing approaches with self-limiting characteristics are summarized with a particular focus on Langmuir-Blodgett assembly and LbL assembly. Additively manufactured electronic thin films with properties of conductors, semiconductors, and dielectrics are reviewed, followed by a discussion of their application in various electronics, such as field-effect transistors, sensors, memory devices, photodetectors, light-emitting diodes, and electrochromic devices. Finally, challenges and future developments of these approaches are proposed. The resulting analysis reveals promising opportunities of nanoadditive manufacturing for the solution-based fabrication of electronic devices.

Enzymeless electrochemical determination of hydrogen peroxide at a heteropolyanion-based composite film electrode

For the first time, a sensitive and efficient composite film of [PB/WV–Pt@Pd]₆was constructed for H₂O₂detection.

Two-Dimensional WO3 Nanosheets Chemically Converted from Layered WS2 for High-Performance Electrochromic Devices

Two-dimensional (2D) transitional metal oxides (TMOs) are an attractive class of materials due to the combined advantages of high active surface area, enhanced electrochemical properties, and stability. Among the 2D TMOs, 2D tungsten oxide (WO₃) nanosheets possess great potential in electrochemical applications, particularly in electrochromic (EC) devices. However, feasible production of 2D WO₃ nanosheets is challenging due to the innate 3D crystallographic structure of WO₃. Here we report a novel solution-phase synthesis of 2D WO₃ nanosheets through simple oxidation from 2D tungsten disulfide (WS₂) nanosheets exfoliated from bulk WS₂ powder. The complete conversion from WS₂ into WO₃ was confirmed through crystallographic and elemental analyses, followed by validation of the 2D WO₃ nanosheets applied in the EC device. The EC device showed color modulation of 62.57% at 700 nm wavelength, which is 3.43 times higher than the value of the conventional device using bulk WO₃ powder, while also showing enhancement of ∼46.62% and ∼62.71% in switching response-time (coloration and bleaching). The mechanism of enhancement was rationalized through comparative analysis based on the thickness of the WO₃ components. In the future, 2D WO₃ nanosheets could also be used for other promising applications such as sensors, catalysis, thermoelectric, and energy conversion.

Moisture-Permeable, Humidity-Enhanced Gas Barrier Films Based on Organic/Inorganic Multilayers

Gas barrier films with water-vapor-permeability have exhibited broad application prospects in gas separation and dehumidification. Herein, multilayer films comprised of layered double hydroxides (LDH) nanosheets and carboxymethyl cellulose sodium (CMC) were fabricated via layer-by-layer assembly. The resulting (LDH/CMC) _n films show excellent gas barrier properties, which are ascribed to the significantly increased pathway for gas permeation originating from the large aspect ratio and high orientation of two-dimensional LDH nanosheets. Unlike traditional gas barrier films with nonselective blocking effect for various gases (including water vapor), the (LDH/CMC) _n films exhibit an unusual moisture permselective property. The moisture-permeable property was related to the hygroscopicity of CMC and hydrophilicity of LDH, which can enrich the water molecules from the surroundings and aggrandize the osmotic pressure for water vapor, resulting in an uncommon improvement of water vapor transmission. It is interesting to find that the (LDH/CMC) _n films exhibit enhanced gas (O₂, CO₂, CH₄, and N₂) barrier properties upon treatment in a humid environment, due to the formation of hydrogen bonds between the infiltrated water molecules and hydrophilic groups in CMC, thus padding the interstitial space of the CMC molecular chains and increasing the gas transmission path. The reduction of free volume and extension of the gas transmission path further enhance the gas barrier properties of (LDH/CMC) _n films. Moreover, the (LDH/CMC) _n films represent the water vapor permselective property in mixed gas (including O₂, CO₂, CH₄, N₂, and water vapor), while maintaining the barrier for other gases, which can be potentially applied in air dehydration and dehumidification of natural gas.

Large-Scale Multifunctional Electrochromic-Energy Storage Device Based on Tungsten Trioxide Monohydrate Nanosheets and Prussian White

A high-performance electrochromic-energy storage device (EESD) is developed, which successfully realizes the multifunctional combination of electrochromism and energy storage by constructing tungsten trioxide monohydrate (WO₃·H₂O) nanosheets and Prussian white (PW) film as asymmetric electrodes. The EESD presents excellent electrochromic properties of broad optical modulation (61.7%), ultrafast response speed (1.84/1.95 s), and great coloration efficiency (139.4 cm² C^-1). In particular, remarkable cyclic stability (sustaining 82.5% of its initial optical modulation after 2500 cycles as an electrochromic device, almost fully maintaining its capacitance after 1000 cycles as an energy storage device) is achieved. The EESD is also able to visually detect the energy storage level via reversible and fast color changes. Moreover, the EESD can be combined with commercial solar cells to constitute an intelligent operating system in the architectures, which would realize the adjustment of indoor sunlight and the improvement of physical comfort totally by the rational utilization of solar energy without additional electricity. Besides, a scaled-up EESD (10 × 11 cm²) is further fabricated as a prototype. Such promising EESD shows huge potential in practically serving as electrochromic smart windows and energy storage devices.

Substrate-Friendly Growth of Large-Sized Ni(OH)2 Nanosheets for Flexible Electrochromic Films

Large-area, 2D, anisotropic, direct growth of nanostructures is considered an effective and straightforward way to readily fulfill transparent, flexible technology requirements. In addition, formation of thin hybrid structures by combining with another 2D material brings about dimensional advantages, such as intimate heterostructure functionalities, large specific area, and optical transparency. Here, we demonstrate 2D planar growth of thin Ni(OH)₂ nanosheets on arbitrary rigid and soft supports, by exploiting the growth strategies of oriented attachment induced by interfacial chemistry and the intrinsic driving force of layered structure constitution. Moreover, large-scale 2D heterohybrids have successfully been prepared by direct conformal growth of Ni(OH)₂ nanosheets overlying MoO₃ nanobelts. Unlike the exfoliation and transfer of 2D materials technique, this approach minimizes multiple process contamination and physical-handling structural defects. Accordingly, proof-of-concept flexible electrochromism is demonstrated in view of its prerequisite to the access of a large homogeneous material coating. The as-synthesized 2D layered structure affirms its optical and electrochemical superiority through the display of wide optical modulation, high coloration efficiency, good cyclic stability, and flexibility.

Rich surface Co(iii) ions-enhanced Co nanocatalyst benzene/toluene oxidation performance derived from Co(II)Co(III) layered double hydroxide

A hierarchical CoCo layered double hydroxide (LDH) nanostructure was constructed through a facile topochemical transformation route under a dynamic oxygen atmosphere. Self-assembled coral-like CoAl LDH nanostructures via the homogeneous precipitation method were also inspected under different ammonia-releasing reagents and solvents. Benzene and toluene were chosen as probe molecules to evaluate their catalytic performance over the metal oxide CoCoO and CoAlO calcined from their corresponding LDH precursors. Nanocatalyst of trivalent Co ions replaced Al(3+) ions in the bruited-like layer had a higher catalytic activity (T99(benzene) = 210 °C and T99(toluene) = 220 °C at a space velocity = 60 000 mL g(-1) h(-1)). Raman spectroscopy, XPS and H2-TPR demonstrated the existence of abundant high valence Co ions that serve as active sites. TPD verified the types of active oxygen species and surface acid properties. It was concluded that the high valence Co ions induced excellent low-temperature reducibility. Surface Lewis acid sites and the surface Oads/Olatt molar ratio (0.61) played relevant roles in determining its catalytic oxidation performance. Our design in this work provides a promising approach for the development of nanocatalysts with exposed desirable defects.

Inkjet-printed all solid-state electrochromic devices based on NiO/WO3 nanoparticle complementary electrodes

Nanostructured thin films are important in the fields of energy conversion and storage. In particular, multi-layered nanostructured films play an important role as a part of the energy system for energy saving applications in buildings. Inkjet printing is a low-cost and attractive technology for patterning and deposition of multi-layered nanostructured materials on various substrates. However, it requires the development of a suitable ink formulation with optimum viscosity, surface tension and evaporation rate for various materials. In this study, a versatile ink formulation was successfully developed to prepare NiO and WO3 nanostructured films with strong adhesion to ITO coated glass using inkjet printing for energy saving electrochromic applications. We achieved a high performance electrochromic electrode, producing porous and continuous electrochromic films without aggregation. The NiO film with 9 printed layers exhibits an optical modulation of 64.2% at 550 nm and a coloration efficiency (CE) of 136.7 cm(2) C(-1). An inkjet-printed complementary all solid-state device was assembled, delivering a larger optical modulation of 75.4% at 633 nm and a higher CE of 131.9 cm(2) C(-1) among all solid-state devices. The enhanced contrast is due to the printed NiO film that not only performs as an ion storage layer, but also as a complementary electrochromic layer.

Electrodeposition of Prussian blue films on Ni3Si2O5(OH)4 hollow nanospheres and their enhanced electrochromic properties

Porous PB films were electrodeposited on Ni₃Si₂O₅(OH)₄ hollow nanospheres, resulting in enhanced electrochromic properties due to the coarse substrate.