Nanowire Network Electrodes Research Articles

Active Site Implantation for Ni(OH)2 Nanowire Network Achieves Superior Hybrid Seawater Electrolysis at 1 A cm−2 with Record‐Low Cell Voltage

AbstractDirect seawater electrolysis provides a grand blueprint for green hydrogen (H2) technology, while the high energy consumption has severely hindered its industrialization. Herein, a promising active site implantation strategy is reported for Ni(OH)2 nanowire network electrode on nickel foam substrate by Ru doping (denoted as RuNi(OH)2 NW2/NF), which can act as a dual‐function catalyst for hydrazine oxidation and hydrogen evolution, achieving an ultralow working potential of 114.6 mV to reach 1000 mA cm−2 and a small overpotential of 30 mV at 10 mA cm−2, respectively. Importantly, using the two‐electrode hydrazine oxidation assisted seawater electrolysis, it can drive a large current density of 500 mA cm−2 at 0.736 V with over 200 h stability. To demonstrate the practicability, a home‐made flow electrolyzer is constructed, which can realize the industry‐level rate of 1 A cm−2 with a record‐low voltage of 1.051 V. Theoretical calculations reveal that the Ru doping activates Ni(OH)2 by upgrading d‐band centers, which raises anti‐bonding energy states and thus strengthens the interaction between adsorbates and catalysts. This study not only provides a novel rationale for catalyst design, but also proposes a feasible strategy for direct alkaline seawater splitting toward sustainable, yet energy‐saving H2 production.

First-principles study of mercaptoundecanoic acid molecule adsorption and gas molecule penetration onto silver surface: an insight for corrosion protection.

Recently, 11-mercaptoundecanoic acid (MUA) molecule has attracted attention as a promising passivation agent of Ag nanowire (NW) network electrode for corrosion inhibition, but the underneath mechanism has not been elaborated. In this work, we investigate adsorption of MUA molecule on Ag(1 0 0) and Ag(1 1 1) surface, adsorption of air gas molecules of H2O, H2S and O2 on MUA molecular end surface, and their penetrations into the Ag surface using the first-principles calculations. Our calculations reveal that the MUA molecule is strongly bound to the Ag surface with the binding energies ranging from -0.47 to -2.06 eV and the Ag-S bond lengths of 2.68-2.97 Å by Lewis acid-base reaction. Furthermore, we find attractive interactions between the gas molecules and the MUA@Ag complexes upon their adsorptions and calculate activation barriers for their migrations from the outermost end of the complexes to the top of Ag surface. It is found that the penetrations of H2O and H2S are more difficult than the O2 penetration due to their higher activation barriers, while the O2 penetration is still difficult, confirming the corrosion protection of Ag NW network by adsorbing the uniform monolayer of MUA. With these findings, this work can contribute to finding a better passivation agent in the strategy of corrosion protection of Ag NW network electrode.

Electroplated core\u2013shell nanowire network electrodes for highly efficient organic light-emitting diodes

In this study, we performed metal (Ag, Ni, Cu, or Pd) electroplating of core–shell metallic Ag nanowire (AgNW) networks intended for use as the anode electrode in organic light-emitting diodes (OLEDs) to modify the work function (WF) and conductivity of the AgNW networks. This low-cost and facile electroplating method enabled the precise deposition of metal onto the AgNW surface and at the nanowire (NW) junctions. AgNWs coated onto a transparent glass substrate were immersed in four different metal electroplating baths: those containing AgNO3 for Ag electroplating, NiSO4 for Ni electroplating, Cu2P2O7 for Cu electroplating, and PdCl2 for Pd electroplating. The solvated metal ions (Ag+, Ni2+, Cu2+, and Pd2+) in the respective electroplating baths were reduced to the corresponding metals on the AgNW surface in the galvanostatic mode under a constant electric current achieved by linear sweep voltammetry via an external circuit between the AgNW networks (cathode) and a Pt mesh (anode). The amount of electroplated metal was systematically controlled by varying the electroplating time. Scanning electron microscopy images showed that the four different metals (shells) were successfully electroplated on the AgNWs (core), and the nanosize-controlled electroplating process produced metal NWs with varying diameters, conductivities, optical transmittances, and WFs. The metal-electroplated AgNWs were successfully employed as the anode electrodes of the OLEDs. This facile and low-cost method of metal electroplating of AgNWs to increase their WFs and conductivities is a promising development for the fabrication of next-generation OLEDs.

Stretchable electrochromic devices based on embedded WO3@AgNW Core-Shell nanowire elastic conductors

Stretchable electrochromic devices (SECDs) have steadily attracted widespread attention in wearable devices. However, the delamination of device architectures (electrochromic layer, conductive layer and substrate) and poor chemical stability of conductive layer (silver nanowires (AgNWs)) are the key issues to be resolved to ensure the practical applications of flexible electrochromic devices. Herein, we designed a flexible and stretchable WO3@AgNW-PrePDMS (Pre-cured Polydimethylsiloxane) electrode, through integrated and embedded design, to build a high-performance electrochromic device. The integration of electrochromic layer and conductive layer in the electrode is fabricated via a WO3@AgNW core–shell structure. And embed the core–shell structure into the flexible substrate PDMS to form WO3@AgNW-PrePDMS electrode. This electrode architecture can prevent the delamination of the stretchable electrode during bending tests. Moreover, WO3 as a shell structure protects the conductive material AgNW to prevent its oxidation and improve the stability of the conductive substrate. The WO3@AgNW-PrePDMS electrode displays outstanding electrochemical stabilities and excellent bi-functionalities (flexible conductive film and electrochromic electrode): high conductivity (12 Ω/sq) as flexible transparent conductive film and wide optical modulation range (ΔT = 72% at 550 nm) as electrochromic electrode. The stretchable WO3@AgNW-PrePDMS electrode can still maintain stable electrical conductivity (ΔR/R≈8.3% and 14%) and electrochromic performance (90% and 92% retention) after 20,000 bending cycles and stretching to 70%, indicating the excellent mechanical flexibility. The WO3@AgNW core–shell nanowire network electrodes with embedded structures can be a strong candidate for wearable electrochemical energy devices in the future.

Effect of macroscale mesh design of metal nanowire networks on the conductive properties for stretchable electrodes

Elastic, deformable electrodes have attracted substantial interest owing to their applicability in unconventional stretchable devices. In this study, we investigate the effect of tensile strain on the conductive properties of gold nanowire (AuNW) network electrodes with macroscale mesh structures (mesh-shaped AuNW network electrodes) and the mechanism by which the mesh structure affects its conductivity, with the aim of maintaining a stable conductivity as the electrodes are stretched. At 150% elongation, the proposed AuNW macroscale mesh exhibited a relative resistance change (ΔR/R0) of 11, as opposed to 30 for AuNW network electrodes without a mesh structure. Microstructural analysis revealed that resistance changes in the mesh-shaped AuNW network electrodes depend on the electrode stretching direction and the current direction within the network. Our experimental and analytical results provide a basis for optimizing the mesh design for metal nanowire networks used in stretchable electrodes.

Superstable copper nanowire network electrodes by single-crystal graphene covering and their applications in flexible nanogenerator and light-emitting diode

Copper nanowires (CuNWs), with excellent electronic properties and high cost-effectiveness, have tremendous potential in the field of transparent conductive electrodes for flexible electronics, large touch screen display and triboelectric energy harvesters, while their vulnerability to oxidation in air has impeded possible practical applications. Fortunately, it has been recognized that graphene encapsulation of CuNWs is capable of protecting CuNWs. However, neither self-assembled reduced graphene oxide nor chemical vapor deposition-grown polycrystalline graphene coatings can guarantee full protection to CuNWs, due to their ubiquitous voids, grain boundaries and wrinkles that allow water and oxygen molecules to pass through and result in the accelerated electrochemical corrosion at the graphene-copper interface, especially under folding conditions. Herein, we demonstrate a sandwich-structured single-crystal graphene/copper nanowire network/UV-curable resin (SCG/CuNW/UVR) composite film with ultrahigh electronic performance stability. The SCG/CuNW/UVR electrode exhibits a good optical and electrical performance (~19 Ω sq−1 under 84.3% transmittance), excellent mechanical robust and remarkably high oxidation resistance (ΔR/R0 < 0.2 within 180 days), in sharp contrast with the bare CuNWs (ΔR/R0 > 1 after 1 day) and polycrystalline graphene-covered CuNWs counterparts (ΔR/R0 > 1 after 7 days). Furthermore, the SCG/CuNW/UVR electrodes can replace indium tin oxide (ITO) electrodes to construct the triboelectric nanogenerators (TENG) and quantum dot light emitting diodes (QLED), comparable to the flexible commercial ITO counterparts. The fabrication of such high-performance SCG/CuNW/UVR electrode is facile to be scaled-up with low cost, providing the feasibility for industrial applications of flexible ITO-free electronic and optoelectronic devices.

Improving thermal and electrical stability of silver nanowire network electrodes through integrating graphene oxide intermediate layers

Silver nanowire (Ag NW)-based flexible and transparent electrodes are a promising candidate for various electronic and optoelectronic applications. However, thermal and electrical instabilities of Ag NW networks during operation and post treatments need to be improved for practical applications. In this work, Ag NW/Graphene Oxide (GO) hybrid films with a multilayer structure were developed, in which transparent GO sheets were inserted between Ag NWs. For the pristine Ag NW networks, contacted NWs exhibited poorer thermal stability than individual NWs as faster Ag diffusion between NWs led to the breakage of the junctions at working temperatures, hence leading to the overall device failure. In contrast, the GO intermediate layers hindered the Ag diffusion between NWs in the Ag NW/Graphene Oxide hybrid films and maintained the junction structure, giving rise to enhanced thermal stability compared to the pristine networks and the GO-covered samples. For electrical tests, unlike the network degradation under annealing treatments, a local deterioration perpendicular to the current flow was directly observed after electrical breakdown, which was attributed to high local temperature under large applied voltage. The electrical failure of the devices was related to the network structure and defects. Furthermore, the pristine devices showed notable variation of failure voltage, which in the hybrid devices is more uniform and improved in general.

A facile way for scalable fabrication of silver nanowire network electrodes for high-performance and foldable smart windows

Ag NW TCE based SPDs show high performance (optical modulation 60.2%; switching time 21 s) and excellent flexibility (folded 180°).

ORGANIC SOLAR CELL WITH SPDA: AG NANOWIRE NETWORK

In this study, Sulfonated poly (diphenylamine): Ag nanowire network transparent conductive electrode was prepared that is expected to have high transparency and low resistance for organic solar cells. The resistance value was 10 Ωsq-1 and the optical permeability value was 88% with Sulfonated poly (diphenylamine): Ag nanowire network electrode. By using the electrode in organic solar cell, the solar cell efficiency was obtained 2.7%. The prepared Sulfonated poly (diphenylamine): Ag nanowire network electrode is an alternative to Indium tin oxide for use in organic electronic devices as a promising electrode and can also be used in flexible electronic applications.

Study on the oxidation of copper nanowire network electrodes for skin mountable flexible, stretchable and wearable electronics applications

Copper nanowires (Cu NWs) are suitable material as an electrode for flexible, stretchable and wearable devices due to their excellent mechanical properties, high transparency, good conductivity, and low cost, but oxidation problem limits their practical use and application. In order to use Cu NWs as an electrode for advanced flexible, stretchable and wearable devices attached directly to the skin, the influence of the body temperature on the oxidation of Cu NWs needs to be investigated. In this paper, the oxidation behavior of Cu NWs at high temperature (more than 80 °C) as well as body temperature is studied which has been remained largely questionable to date, and an effective encapsulation method is proposed to prevent the oxidation of Cu NWs electrode in the range of body temperatures.

Effective passivation of Ag nanowire network by transparent tetrahedral amorphous carbon film for flexible and transparent thin film heaters

We developed effective passivation method of flexible Ag nanowire (NW) network electrodes using transparent tetrahedral amorphous carbon (ta-C) film prepared by filtered cathode vacuum arc (FCVA) coating. Even at room temperature process of FCVA, the ta-C passivation layer effectively protect Ag NW network electrode and improved the ambient stability of Ag NW network without change of sheet resistance of Ag NW network. In addition, ta-C coated Ag NW electrode showed identical critical inner and outer bending radius to bare Ag NW due to the thin thickness of ta-C passivation layer. The time-temperature profiles demonstrate that the performance of the transparent and flexible thin film heater (TFH) with the ta-C/Ag NW network is better than that of a TFH with Ag NW electrodes due to thermal stability of FCVA grown ta-C layer. In addition, the transparent and flexible TFHs with ta-C/Ag NW showed robustness against external force due to its high hardness and wear resistance. This indicates that the FCVA coated ta-C is promising passivation and protective layer for chemically weak Ag NW network electrodes against sulfur in ambient.

Ambient-Stable and Durable Conductive Ag-Nanowire-Network 2-D Films Decorated with a Ti Layer

Highly stable and durable conductive silver nanowire (Ag NW) network electrode films were prepared through decoration with a 5-nm-thick Ti layer. The Ag NW network 2-D films showed sheet resistance values as low as 32 ohm/sq at 88% transparency when decorated with Ti. These 2-D films exhibited a 30% increase in electrical conductivity while maintaining good stability of the films through enhanced resistance to moisture and oxygen penetration as a result of the protective effect of the Ti layer.

Epitaxial-Growth-Induced Junction Welding of Silver Nanowire Network Electrodes.

In this study, we developed a roll-to-roll Ag electroplating process for metallic nanowire electrodes using a galvanostatic mode. Electroplating is a low-cost and facile method for deposition of metal onto a target surface with precise control of both the composition and the thickness. Metallic nanowire networks [silver nanowires (AgNWs) and copper nanowires (CuNWs)] coated onto a polyethylene terephthalate (PET) film were immersed directly in an electroplating bath containing AgNO3. Solvated silver ions (Ag+ ions) were deposited onto the nanowire surface through application of a constant current via an external circuit between the nanowire networks (cathode) and a Ag plate (anode). The amount of electroplated Ag was systematically controlled by changing both the applied current density and the electroplating time, which enabled precise control of the sheet resistance and optical transmittance of the metallic nanowire networks. The optimized Ag-electroplated AgNW (Ag-AgNW) films exhibited a sheet resistance of ∼19 Ω/sq at an optical transmittance of 90% (550 nm). A transmission electron microscopy study confirmed that Ag grew epitaxially on the AgNW surface, but a polycrystalline Ag structure was formed on the CuNW surface. The Ag-electroplated metallic nanowire electrodes were successfully applied to various electronic devices such as organic light-emitting diodes, triboelectric nanogenerators, and a resistive touch panel. The proposed roll-to-roll Ag electroplating process provides a simple, low-cost, and scalable method for the fabrication of enhanced transparent conductive electrode materials for next-generation electronic devices.

Fabrication of a Combustion-Reacted High-Performance ZnO Electron Transport Layer with Silver Nanowire Electrodes for Organic Solar Cells.

Herein, a new methodology for solution-processed ZnO fabrication on Ag nanowire network electrode via combustion reaction is reported, where the amount of heat emitted during combustion was minimized by controlling the reaction temperature to avoid damaging the underlying Ag nanowires. The degree of participation of acetylacetones, which are volatile fuels in the combustion reaction, was found to vary with the reaction temperature, as revealed by thermogravimetric and compositional analyses. An optimized processing temperature of 180 °C was chosen to successfully fabricate a combustion-reacted ZnO and Ag nanowire hybrid electrode with a sheet resistance of 30 Ω/sq and transmittance of 87%. A combustion-reacted ZnO on Ag nanowire hybrid structure was demonstrated as an efficient transparent electrode and electron transport layer for the PTB7-Th-based polymer solar cells. The superior electrical conductivity of combustion-reacted ZnO, compared to that of conventional sol-gel ZnO, increased the external quantum efficiency over the entire absorption range, whereas a unique light scattering effect due to the presence of nanopores in the combustion-derived ZnO further enhanced the external quantum efficiency in the 450-550 nm wavelength range. A power conversion efficiency of 8.48% was demonstrated for the PTB7-Th-based polymer solar cell with the use of a combustion-reacted ZnO/Ag NW hybrid transparent electrode.

Roll-to-roll redox-welding and embedding for silver nanowire network electrodes.

We developed a continuous roll-to-roll redox-welding and embedding method for the fabrication of electrodes of silver nanowire (AgNWs) networks. The roll-to-roll welding method involved a sequence of oxidation and reduction reactions in an aqueous solution. The redox-welding significantly decreased the sheet resistance of the AgNW film owing to the strong fusion and interlocking at the nanowire junction, while the optical transmittance was maintained. The first oxidation step using HNO3 generated ionized silver (Ag+) which got re-deposited onto the nanowire junctions via an autocatalytic reaction. The oxide layers, which formed on the nanowire surface by both air exposure and the first step of oxidation, were removed by the second reduction step using NaBH4. The redox-welded AgNW electrodes exhibited a sheet resistance of 11.3 Ω sq-1 at the optical transmittance of 90.5% at 550 nm. Furthermore, redox-welding of the AgNWs significantly enhanced their mechanical robustness compared to that of the as-coated AgNWs. The redox-welded AgNWs embedded in a UV curable resin, using a roll-to-roll embedding process, were successfully applied as anode electrodes for large-area and flexible organic light emitting diodes (OLEDs). The device performance is superior to that of a device based on the as-coated AgNW electrode, and is also comparable to that of a device using commercial ITO as the electrode. The redox-welding and embedding processes provide a facile and reliable method for fabricating large-area transparent flexible electrodes for next-generation flexible optoelectronic devices.

Hydrophobic and stretchable Ag nanowire network electrode passivated by a sputtered PTFE layer for self-cleaning transparent thin film heaters.

We demonstrated hydrophobic, flexible/stretchable, and transparent electrodes made up of Ag nanowire (NW) networks passivated by a sputtered polytetrafluoroethylene (PTFE) layer to produce self-cleaning transparent thin film heaters (TFHs). Using carbon nanotubes and a PTFE mixed conducting target, we successfully sputtered a transparent PTFE layer on the Ag NW network using mid-frequency magnetron sputtering. The hydrophobic surface of the PTFE/Ag NW electrodes led to water-repelling and self-cleaning transparent Ag NW electrodes, which are beneficial for transparent TFH-based smart windows. Furthermore, hydrophobic PTFE/Ag NW electrodes coated on polyethylene terephthalate (PET) and polyurethane (PU) substrates showed outstanding flexibility and stretchability, respectively, due to the capping effect of the PTFE layer. Based on outer/inner bending and stretching test results, we demonstrated the superior mechanical properties of the PTFE/Ag NW electrode compared to a bare Ag NW electrode. Finally, we investigated the feasibility of the PTFE/Ag NW film coated on a PU substrate as a transparent and stretchable electrode for stretchable and self-cleaning transparent TFHs. The effective heat generation of the stretchable PTFE/Ag NW electrode indicates the potential for energy-efficient multi-functional PTFE/Ag NW-based TFHs attached to automobile windows.

A new high‐performance blue to transmissive electrochromic material and use of silver nanowire network electrodes as substrates

ABSTRACTSynthesis of a novel, high‐performance blue to transmissive switching electrochromic material is described. The polymer (P1) was prepared by both electrochemical (P1E) and chemical (P1C) means from the corresponding monomer. The electrochemically synthesized polymer (P1E) revealed 64% optical contrast change (on ITO) in the visible region and very fast switching times of 0.32 s (coloration) and 0.90 s (bleaching). On the other hand, the chemically synthesized, solution processable polymer (P1C) also showed a high optical contrast value (49%, on ITO) with very fast switching times of 0.86 s for coloration and 0.57 s for bleaching. These high optical contrast values coupled with fast switching times place these materials along with high‐performance blue to transmissive electrochromic polymers. Significantly, these improved characteristics were achieved by side chain engineering of a known, inferior blue to transmissive polymer, PBEBT. Towards fabrication of flexible electrochromic devices, the performance of P1C was also tested on silver nanowire network electrodes. Even though the full potential of the material could not be demonstrated, a good optical contrast of 24% was achieved using these electrodes. Under the same potential range allowed by silver nanowire network electrodes, P1C on ITO showed an optical contrast of 30%. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1680–1686

Blue Laser Annealing of Ag Nanowire Electrodes for Flexible Thin Film Heaters

A blue laser annealing process was investigated to improve the connectivity of slot die-coated Ag nanowire (NW) network electrodes intended for use in flexible and transparent thin film heaters (TFHs). The electrical, optical, and morphological properties of blue-laser-irradiated Ag NW network electrodes were investigated as functions of the scanning speed apllied during annealing. Due to effective welding of Ag NWs that were formerly under only physical contact, and due to complete removal of the polyvinylpyrrolidone on the surface of each Ag NW, the blue laser annealing yielded Ag NW networks that exhibited decreased sheet resistance with no change of optical transmittance. Because the laser annealing decreased the Ag NW network's sheet resistance, the TFH based on the blue-laser-irradiated Ag NW electrodes showed higher saturation temperature at lower input DC voltage compared to the control device.

Silver Nanowire/Conducting Polymer Nanocomposite Electrochromic Supercapacitor Electrodes

Color-changing energy storage devices that can easily communicate with the user carry the potential to be integrated into smart electronics. In this work, nanocomposite electrochromic supercapacitor electrodes were fabricated with silver nanowire (Ag NW) network electrodes and a green to transmissive electrochromic polymer, PDOPEQ. High transparency and conductivity of Ag NW network current collectors allowed the fabrication of electrochromic supercapacitors and investigation of the spectroelectrochemical and electrochemical properties of the PDOPEQ. Previously reported electrochromic properties such as long term electrochromic switching stability and vibrant color change for PDOPEQ were well transferred into electrochromic capacitors. Investigated electrochromic supercapacitors changed their color from vibrant green to transparent with superior characteristics. Specific capacitance of the fabricated nanocomposite electrodes was calculated as 61.5 F g−1 at a current density of 0.1 A g−1 and to the best of our knowledge, one of the highest capacity retention value was obtained upon 20000 galvanostatic charge-discharge cycles. With these color options and electrochemical performance, investigated conducting polymer (CP) holds strong promise to be used in electrochromic supercapacitors.

Templated electrodeposition of vertically aligned copper oxide nanowire arrays on 3D Ni foam substrates for determination of glucosamine in pharmaceutical caplet samples

A copper oxide nanowire network electrode has been fabricated through an electrodeposition procedure using mesoporous silica film as the template on Ni foam.