Reversible Metal Electrodeposition Research Articles

Transparent, High‐Charge Capacity Metal Mesh Electrode for Reversible Metal Electrodeposition Dynamic Windows with Dark‐State Transmission <0.1%

AbstractDynamic windows allow user control over light and heat flow to save energy and maximize comfort. Reversible metal electrodeposition (RME) dynamic windows can uniquely tint to a color‐neutral privacy state (0.1% visible light transmission). The design parameters of transparent metal mesh counter electrodes for high‐contrast RME dynamic windows: high transparency, charge capacity and surface area with low haze, sheet resistance and cost are discussed, concluding that woven metal meshes meet these design parameters. Electroplated current is measured on an indium tin oxide electrode and two meshes with different wire spacings, showing the meshes’ cylindrical geometry enable them to draw more current per square area. The mesh material composition is analyzed to ensure cycling durability in a CuBi electrolyte by developing a transparent mesh with an inert core (stainless steel, SS), a thin Au coating, and a high charge‐capacity (1.5 C cm−2) CuBi outer coating. The study demonstrates that the films maintain a consistent Cu:Bi ratio and optical properties after 250 privacy cycles or 1500 cycles to 10% transmission, showing that the Cu and Bi coating is effective in keeping the films from becoming Cu rich with cycling. Finally, a 100 cm2 device with excellent uniformity and color neutrality is demonstrated.

Multicolor electrochromic device based on reversible metal electrodeposition of Bi-Cu with controlled morphology and composition ratio

Reversible metal electrodeposition (RME) devices with optical tunability in multiple optical states are exciting alternatives to conventional electrochromic (EC) smart windows. In this work, we studied Bi-Cu electrodeposition carefully by applying the step-potential method and constant-potential method. Five optical states—transparent, purple transparent, purple mirror, yellow transparent and yellow mirror—are achieved, which is firstly reported in Bi-Cu RME devices. The acquisition of polychromatic states could be attributed mainly to the localized surface plasmon resonance (LSPR) effect, which is related to morphologies and composition ratios of the electrodeposited bimetal films. Our device exhibits excellent cycling stability switched between purple transparent state and transparent state, maintaining 80% transmittance window after 2500 cycles. The yellow mirror state generated by the step-potential method shows superior color retention stability and heat blocking ability than the purple mirror state generated by the constant-potential method, meaning that the more uniform and denser metal film deposited by the step-potential method is more suitable to the EC applications. In brief, Our RME device exhibits multiple optical states, competitive switching speeds, superior cycling stability, color retention stability and heat blocking ability, making it promising for use in light modulating devices, such as smart windows and information displays.

Constructing Low N/P Ratio Sodium-Based Batteries by Reversible Na Metal Electrodeposition on Sodiophilic Zinc-Metal-Decorated Hard Carbons

Constructing Low N/P Ratio Sodium-Based Batteries by Reversible Na Metal Electrodeposition on Sodiophilic Zinc-Metal-Decorated Hard Carbons

A Solar Water-Heating Smart Window by Integration of the Water Flow System and the Electrochromic Window Based on Reversible Metal Electrodeposition.

Various smart windows with dynamic modulation of the light transmittance have been developed rapidly in recent years. However, current design of the smart windows can only modulate the indoor solar irradiation instead of effectively utilize them. Here, a solar water‐heating (SWH) smart window is proposed by the integration of the traditional electrochromic window and the water flow system, which can not only provide dynamic daylight modulation but also harvest the solar energy and store them by heating water. In the SWH window, the reversible metal electrodeposition (RME) not only provides daylight modulation but also provides metal layer working as a flat‐plate solar collector for energy harvesting. Compared with traditional electrochromic windows, the SWH window with a water flow system can more effectively modulate the indoor temperature, owing to the significantly enhanced tunability of the thermal irradiation from the window. Compared with water‐flow windows, the RME provide a metallic layer for efficient light harvesting, up to 42% solar energy can be effectively harvested and stored as hot water. Such an SWH smart window is promising to reduce the heating, lighting, and air conditioning energy consumption, which may bring new insights in the design of the next‐generation green buildings.

Robust Trioptical-State Electrochromic Energy Storage Device Enabled by Reversible Metal Electrodeposition

Reversible electrochemical mirror (REM) electrochromic devices based on reversible metal electrodeposition are exciting alternatives compared with conventional electrochromic because they offer electrochemical tunability in multiple optical states, long durability, and high contrast. Different from conventional electrochromic materials, of which the color change depends on the intercalation/deintercalation of ions into electrochromic films, the change in the optical states of REMs is based on the reversible electrodeposition and dissolution of metal. In this study, a REM electrochromic device with a Cu hybrid electrolyte composed of aqueous and nonaqueous components is proposed, which serves as an electrolyte reservoir that hosts Cu ions for reversible electrodeposition/dissolution. The hybrid electrolyte promotes the electrochemical reversibility of the Cu redox, an enhanced electrochromic performance, and a robust cycling stability of 5000 cycles (minor degradation of 4.71%). The investigation of the discharging/charging of the Cu hybrid REM device reveals that the Cl–/ClO– redox mechanism occurs at the cathode. Finally, an unprecedented dual-functional Cu hybrid REM energy storage device has been realized.

Reversible Electrodeposition of Ni and Cu for Dynamic Windows

Reversible metal electrodeposition is a promising method for constructing dynamic windows with electronically switchable transparency. Through the reduction of lighting, heating, and cooling costs, these windows reduce energy consumption. Here, we design new electrolytes for reversible metal electrodeposition on tin-doped indium oxide electrodes based on the co-electrodeposition of Ni and Cu. We determined that synergistic effects between Ni and Cu facilitate spectroelectrochemical reversibility in contrast to the individual electrodeposition of these metals. The most reversible electrolytes contain chloride to improve electrodeposition kinetics and sulfamate ions to prevent the formation of dendrites. In addition to improving the color neutrality of the electrodeposits, nickel sulfamate in the electrolytes serves as a source of sulfamate ions that is soluble without added acid. After investigating the functions of the different electrolyte components, we then evaluated the performance of 25 cm2 two-electrode Ni-Cu dynamic windows.

Ionic Liquid Electrolyte-Based Switchable Mirror with Fast Response and Improved Durability.

Electrochemically tunable devices based on reversible metal electrodeposition have attracted extensive attention for energy-saving smart windows, information displays, digital signage, and variable reflectance mirrors, owing to their excellent optical modulation characteristics, low operation voltage, and superb electrochemical stability. Here, we study the effects of ionic liquid (IL)-based electrolytes on electrodeposition of the reversible electrochemical mirrors (REMs) by changing the organic cations of the ILs to obtain devices with the desired spectroelectrochemical and electrodeposited properties. Spectroelectrochemical measurements and scanning electron microscopy images show that organic cations drastically affect the switching speed and cycling durability, which we proposed on the basis of the difference in the absorption energies between cations and Ag(111) surfaces. Higher adsorption energy indicates strong adhesion between organic cations and Ag(111) surfaces, and this strong adsorption would prevent aggregation and agglomeration during the nucleation of Ag nanoparticles (AgNPs), leading to a denser and more compact electrodeposited Ag film and faster switching speeds (3.3 s for coloring and 14.3 s for bleaching). These findings allow us to fabricate dynamic devices that exhibit reversibly switchable light modulation at fast switching speeds and excellent cycling stability over thousands of cycles without attenuation. The combination of rapid switching and durable cycling stability enables tunable windows, which are based on reversible electrodeposition of metal Ag and IL-based electrolytes, make REM devices a competitive and promising alternative to traditional intelligent response materials.

Polymer inhibitors enable >900 cm2 dynamic windows based on reversible metal electrodeposition with high solar modulation

Dynamic windows with adjustable tint give users control over the flow of light and heat to decrease the carbon footprint of buildings and improve the occupants’ comfort. Despite the benefits of dynamic windows, they are rarely deployed in buildings because the existing technology cannot achieve fast and colour-neutral tinting at an agreeable cost. Reversible metal electrodeposition is a promising approach to solve these problems. Here, we demonstrate the use of polymer inhibitors to reversibly deposit metal films with controlled morphology in dynamic windows. The windows that employ the polymer inhibitor can readily tint to below 0.001% visible transmittance in less than 3 min and exhibit high infrared reflectance (>70%), colour-neutral transmittance (C* < 5) and an ultrawide range of optical and solar modulation (ΔTvis = 0.76 and ΔSHGC = 0.56). The polymer inhibitors also increase the efficiency and improve the durability of the windows and enable construction of >900 cm2 dynamic windows with fast response and excellent uniformity.

Reversible Metal Electrodeposition Devices: An Emerging Approach to Effective Light Modulation and Thermal Management

AbstractThe reversible metal electrodeposition device (RMED) is a novel electrochromic application that utilizes the appearance and disappearance of a metal layer to achieve spectrum control. A thin metal film with a thickness of a few tens of nanometers would be highly reflective in the visible and infrared region, making it an ideal material to achieve light and heat modulation. Because of their outstanding spectrum control ability, RMEDs can be applied to displays, smart windows, and thermal camouflage. However, as is the case with many other electrochromic devices, difficulties in device enlargement pose significant challenges to the application of RMEDs. Herein, an overview of the milestone advances of RMEDs is provided, with a focus on their application as smart windows, which is the most extensively studied topic. Recent attempts to improve their open‐circuit stability and designs for device enlargement are highlighted. Finally, insight into the remaining challenges and future prospects in this field is provided.

Electrolytes for reversible zinc electrodeposition for dynamic windows

Reversible Zn electrodeposition electrolytes enable dynamic window with electronically tuneable transmission.

Hybrid Dynamic Windows with Color Neutrality and Fast Switching Using Reversible Metal Electrodeposition and Cobalt Hexacyanoferrate Electrochromism.

Dynamic windows, which electronically switch between clear and dark states on demand, save energy in buildings and automobiles by minimizing the lighting, heating, and cooling costs. In this study, we design dynamic windows by combining reversible metal electrodeposition (RME) and electrochromism, two promising approaches for optoelectronics. These hybrid dynamic windows tint on both electrodes. Reversible Bi and Cu electrodeposition is elicited on the working electrode, while an electrochromic cobalt hexacyanoferrate thin film darkens on the counter electrode. By facilitating plane parallel ion diffusion and dual tinting, this architecture enables dynamic windows to switch more rapidly than devices based on traditional RME schemes. We demonstrate that 25 cm2 devices switch with 58% optical contrast between a transparent and a color-neutral dark state in 20 s. Moreover, these hybrid dynamic windows switch 1000 times without significant degradation in optical performance.

Synthesis dynamics of silver nanowires galvanically displaced by platinum salts: a fabrication route for oxygen reduction electrocatalysts and metal electrodeposition electrodes

The advancement of conductive and flexible thin films is relevant to an assortment of energy applications ranging from organic photovoltaics, fuel cells, lithium ion batteries, and dynamic windows. Here, we develop an inexpensive, fast, and adjustable method to yield nanowire arrays on flexible polyethylene terephthalate substrates for the alkaline oxygen reduction reaction and for reversible metal electrodeposition. Ag nanowires serve as a non-sacrificial template for Pt deposition and allow for the synthesis of bimetallic Pt/Ag nanowires. When not properly controlled, the galvanic displacement reaction occurring at the solid–liquid interface between Ag nanowires and aqueous Pt ions results in nonuniform nucleation and growth profiles, which creates micron-sized gaps in the nanowire arrays. These gaps, which result in poorly conducting thin films, increase in prevalence when immersion length and Pt concentration are increased. Multiple cycles of 10-min immersions in 10 mM K2PtCl4 yield bimetallic Pt/Ag nanowires that maintain the high aspect ratios and conductivities of the initial Ag nanowires, while the added Pt improves electrocatalytic performance and electrochemical durability.

Electrolyte for Improved Durability of Dynamic Windows Based on Reversible Metal Electrodeposition

Summary Electrochromic, “smart” windows allow users to control light and heat flow into and out of buildings or vehicles without sacrificing their view. Despite the appeal of dynamic windows, they have yet to achieve extensive commercialization due to their inability to simultaneously achieve fast, color-neutral tinting over a wide optical dynamic range at a low cost. Reversible metal electrodeposition (RME) is a promising alternative that addresses the drawbacks of existing technologies. Here, we study several possible RME electrolytes at various pHs with different supporting anions. We identify that acidic perchlorate electrolytes permit fully reversible metal electrodeposition without harming the substrate or introducing irreversible side reactions, which was not seen among all other electrolytic compositions. This perchlorate electrolyte shows promising long-term durability, demonstrating 10,000 stable cycles with no evidence of electrode etching. In addition, we construct 15 × 15 cm2 dynamic windows that tint uniformly with fast, color-neutral switching (>60% contrast in

Aqueous alkaline electrolytes for dynamic windows based on reversible metal electrodeposition with improved durability

Dynamic windows based on reversible bismuth and copper electrodeposition switch between clear and opaque states using alkaline aqueous electrolytes enabled by a chelating ligand.

Graphene-based reversible metal electrodeposition for dynamic infrared modulation

Graphene-based dynamic infrared modulation devices were fabricated by reversibly electrodepositing metals on infrared-transparent graphene electrodes.

Controlling the Optical Properties of Dynamic Windows Based on Reversible Metal Electrodeposition

We describe physicochemical strategies that allow for control of the transmission and color of dynamic windows based on reversible metal electrodeposition. The electrolyte composition and voltage profile used for Bi and Cu electrodeposition significantly affect the color of the devices as quantified by La*b* space colorimetry (L = lightness, a* = red/green coordinate, b* = yellow/blue coordinate). First, in terms of electrolyte composition, we find that although increasing the Cu ion concentration improves the maximum attainable opacity of the devices, it decreases the color neutrality of the windows. Second, we demonstrate that altering the electrodeposition voltage profile affects the average size of the metal electrodeposits, which in turn dictates device color during tinting. Through a combination of SEM-EDX imaging and Mie theory calculations, we develop a model that satisfactorily predicts the relationship between electrodeposit morphology and color neutrality. By using pulsed electrodeposition to f...

Dual Tinting Dynamic Windows Using Reversible Metal Electrodeposition and Prussian Blue.

Electronically tintable windows based on reversible metal electrodeposition are a promising alternative to electrochromic materials due to the high optical contrast imparted by the opacity of thin metal films. While traditional metal-based dynamic windows utilize a metal counter electrode frame, metal electrodeposition on the working electrode must be paired with a plane-parallel counter electrode that facilitates transverse ion migration to enable uniform metal electrodeposition on a large scale. In this manuscript, we develop dynamic windows that combine reversible Bi electrodeposition on the working electrode with a Prussian blue counter electrode that acts as both a charge storage layer that intercalates K+ ions and an anodically coloring material. Since both electrodes darken during window tinting, 25 cm2 devices switch with an optical contrast of ∼67.5% at 700 nm in only 3 s, making them the fastest dynamic windows using reversible metal electrodeposition reported on this scale.

Design of Reversible Electroplating Cells for Energy-Saving Windows

Dynamic windows, which allow electronic control over visible light and solar irradiation, enable responsive environments free of glare and unwanted heat. Electronic control over visible light transmittance and solar heat gain coefficients will allow dynamic windows to be integrated with algorithms to optimize for energy efficiency and comfort. The implementation of this technology increases building energy efficiency by 10% compared to traditional, static low-emissivity windows. Dynamic windows based on reversible metal electrodeposition (RME) represent an exciting, new class of electrochromic devices. These RME windows function like a battery by electrochemical movement of metallic ions between a transparent conducting working electrode and a metal mesh or ion-intercalation counter electrode. Metals are ideal light-modulators for dynamic windows because they can be color neutral, inert, photostable, and opaque at 20-30 nanometer thicknesses. Our team has demonstrated metal-based dynamic windows that boast cheap processing, fast switching (<1 minute), and stable performance over thousands of cycles on the 100 cm2 scale. Our current RME windows use an acidic, aqueous halide-based liquid electrolyte that presents technical barriers to device scalability. Due to the inherent voltage drop across the indium tin oxide (ITO) electrode under operating conditions, the electrolyte must exhibit a wide voltage range for uniform metal deposition without undesired side reactions. In an acidic aqueous system, the hydrogen evolution reaction (HER) and ITO oxidation potential set a firm boundary on the voltage range in which the windows can operate. Finally, a liquid electrolyte limits the size of the window due to hydrostatic pressure build up in a vertically oriented window. These design constraints set parameters for developing an electrolyte for RME windows with improved scale and durability. We explore a non-aqueous, non-halide electrolyte that meets these design constraints and is capable of reversibly depositing metals (e.g. Ag and Cu) for RME dynamic windows. The addition of various gel-inducing polymers and electrolyte additives allows us to design windows with reduced hydrostatic pressure build up and improved durability. Utilizing a combination of electrochemical and materials characterization techniques, we present a detailed study of the kinetic and transport properties as well as the morphological and optical effects of this electrolytic system. From these results, we successfully engineered a 400 cm2 window demonstrating fast, uniform transmission change with high optical contrast (~60%), color neutrality, and high cycle life. Developing a strong understanding of reversibly electroplating metals using multivalent metallic ions with variable sizes yields valuable insight to batteries where reversible plating is critical for operation and durability. Further, insights gained from electrolyte-electrode interfaces and interactions in these RME windows can be used to improve fuel cell and battery performance. Reversible Metal Electrodeposition Operating Principle and Schematic: Figure 1

Hybrid dynamic windows using reversible metal electrodeposition and ion insertion

Dynamic windows with electronically controlled transmission reduce glare without obstructing views while increasing the energy efficiency of buildings and automobiles via lighting, heating and cooling savings. Electrochromic materials, which change colour with voltage, are widely explored for use in dynamic windows, but they have not been extensively commercialized due to problems associated with colour, cost, switching speed and durability. Here, we develop a class of dynamic windows that combines reversible metal electrodeposition with ion insertion chemistry. These devices function through the reversible electroplating of Bi and Cu at the working electrode and Li+ insertion in a nickel oxide counter electrode. In one minute, 100 cm2 windows uniformly switch between a clear state with 75% transmission and a colour-neutral black state possessing 10% transmission, which represents a significant improvement over previous metal-based architectures. We demonstrate that these hybrid windows cycle at least 4,000 times without degradation and are compatible with flexible substrates. Lastly, we discuss how this approach can be used to design practical large-scale windows. Metal-based smart windows allow for light and heat transmission control but suffer from poor metal ion diffusion over large areas. Here, the authors demonstrate a 100 cm2 window that is uniformly switchable from clear to black in 60 s by combining reversible metal electrodeposition with ion insertion.

Dynamic Windows Based on Reversible Metal Electrodeposition with Enhanced Functionality

Electronically tintable windows increase the energy efficiency and comfort of buildings and automobiles. Recently, dynamic windows harnessing reversible metal electrodeposition have been explored as a viable alternative to electrochromic materials. In this manuscript, we first construct 25 cm2 dynamic windows with two tin-doped indium oxide (ITO) working electrodes, a metal frame counter electrode, and an aqueous-based electrolyte containing metal ions. This arrangement allows metal electrodeposition to occur simultaneously on both window panes and increases switching speed such that devices switch to ∼30% transmission in 10 s compared to analogous windows with one working electrode which take 30 s to reach the same transmission value. Windows with two working electrodes switch between clear (∼82% transmission at 600 nm) and black (∼8% transmission at 600 nm) states within 30 s, making them among the fastest metal-based dynamic windows reported on this scale. Second, we elicit selective metal electrodeposition on Pt nanoparticles that are attached to ITO substrates via a self-assembled monolayer (SAM). By patterning the SAM of Pt nanoparticles, metal electrodeposition can be spatially controlled on both the macroscale and microscale. Taken together, these results demonstrate the versatility of the reversible metal electrodeposition architecture for dynamic windows.