Large Area Electrodes Research Articles

Research Progress of Photo-/Electro-Driven Thermochromic Smart Windows.

Thermochromic smart windows can automatically control solar radiation according to the ambient temperature. Compared with photochromic and electrochromic smart windows, they have a stronger applicability and lower energy consumption, and have a wide range of application prospects in the field of building energy efficiency. At present, aiming at the challenge of the high transition temperature of thermochromic smart windows, a large amount of innovative research has been carried out via the principle that thermochromic materials can be driven to change their optical performance by photothermal or electrothermal effects at room temperature. Based on this, the research progress of photo- and electro-driven thermochromic smart windows is summarized from VO2-based composites, hydrogels and liquid crystals, and it is pointed out that there are two main development trends of photo-/electro-driven thermochromic smart windows. One is exploring the diversified combination methods of photothermal materials and thermochromic materials, and the other is developing low-cost large-area heating electrodes.

Characterizing the Onset Potential Distribution of Pt/C Catalyst Deposition by a Total Internal Reflection Imaging Method.

A catalytic electrode with extraordinary performances for hydrogen evolution reaction (HER) should achieve a low onset potential of the bulk electrode, as well as its uniform distribution. Herein, a total internal reflection imaging (TIRi) method to characterize the onset potential distribution of the catalytic electrode surface is presented. When the potential scans toward negative in a linear sweep voltammetry, the equivalent refractive index of the electrolyte on the electrode surface will decrease due to H2 microbubbles generation, leading to the increase in optical intensity. Analysis of the relationship between the optical intensity and potential in each region results in the onset potential distribution. The TIRi method reveals poor uniformity and repeatability in the catalytic electrodes which are fabricated by depositing Pt/C catalysts on a porous carbon support with polymer binders (e.g.,Nafion). Further electrochemical stability test also shows poor durability, whose HER onset potential deteriorates from the edge to the middle of these catalytic electrodes. The present TIRi method realizes direct visualization of the activity distribution on the bulk electrode surface, which provides a powerful tool for better fabrication and evaluation of large-area HER electrodes in industrial energy devices.

Gold and silver nanocomposite-based biostable and biocompatible electronic textile for wearable electromyographic biosensors

Wearable biosensors have received significant attention due to the possibility of measuring physiological signals on demand. Particularly, the monitoring of electromyographic (EMG) signals on demand by wearable platforms has significant potential to revolutionize the diagnostics and treatment of neuromuscular diseases and for advancing human–computer interfaces. Electronic textile-based biosensors have several advantages, including the simple scale-up process and the ease of fabricating multiple large area electrodes over the whole body to obtain precise measurements. Hence, the electronic textile production requires an affordable approach to fabricate biocompatible and biostable electronic circuits on textile materials. This work explores the possibility of combining screen printing and electrodeposition techniques to produce a biostable nanocomposite-based EMG biosensor on textile. Screen printing was selected to fabricate conductive fabrics that would ultimately be a highly durable textile-based sensor. Silver paste, including microscale silver flakes, was printed on PET/cotton blended fabrics. However, the microscale silver surface was limited for EMG sensors due to low surface area and toxicity, causing low signal detection performance and skin irritation. Gold nanoparticles (Au NPs) were deposited on silver flakes to address the requirements of high-performance and biocompatible biosensors. We confirmed that the gold functionalization improved electrical and electrochemical performance. In addition, various tests were performed to determine electrochemical and biological stability under physiological conditions. The test results proved that Au NPs have successfully encapsulated the surface of silver flakes, preventing the exposure of the silver to the physiological environment. EMG signal recording was performed to confirm the functionalization effect that improved the signal to noise ratio (SNR) of 12.5 with 120 nm Au NPs. Moreover, EMG sensing from bicep workouts and finger movements showed the high sensitivity of the electronic fabrics. Although the SNR of EMG signals dropped to 7.2 after a 15-time washing test, the stabilized SNR after 5 washing cycles indicated that the Au/Ag biosensors showed washing durability. The study demonstrates that this affordable approach can be considered for large-scale production of wearable EMG biosensors.

Lithiophilic MXene‐Guided Lithium Metal Nucleation and Growth Behavior (Adv. Funct. Mater. 32/2021)

Lithium Metal Batteries In article number 2101261, Seon Joon Kim, Young Soo Yun, and co-workers study lithiophilic surface-guided lithium metal nucleation and growth behaviors using a large-area Ti3C2Tx MXene electrode containing a large number of oxygen and fluorine dual heteroatoms. The lithiophilic MXene substrate significantly affects the surface tension of the lithium metal nuclei as well as the nucleation overpotential, forming highly reversible metal clusters composed of spherical lithium nanoparticles.

On the impedance of a high-frequency capacitive discharge with different excitation methods

Consideration is given to a low-pressure ( << ) capacitive high-frequency discharge with large-area electrodes when it is excited by an electromagnetic field with a frequency from 13 to 900 MHz. General analytical formulas are obtained for the amplitudes of natural waves and the impedance of the discharge. It is taken into account that the excitation of surface waves and higher nonpropagating modes occurs both due to the axial inhomogeneity of the plasma-metal layer structure and due to edge effects at the electrode cut. The higher ampli-tude of the resonance modes in this case (in comparison with the excitation of the discharge by a TEM wave) leads to a greater irregularity in the dependence of the discharge impedance on the electron density. This conclusion is confirmed by the direct calculation of impedance using the Comsol Multiphysics® software.

Bacteria‐driven Single‐inlet Microfluidic Fuel Cell with Spiral Channel Configuration

AbstractWe present a single inlet, spiral‐shaped microfluidic microbial fuel cell (MFC) with porous Paper@Ni anode and Paper@C cathode for energy generation. In the MFC, the anode with a bacterial component is placed along the microchannel side to provide a larger electrode surface area, reduced internal resistance, and enhances mass transport of the 2 % glucose as a substrate for microbial redox reaction. The large electrode area induced by the spiral channel configuration and passive control of the boundary layer enhances the energy output from the fuel cell and eliminates the need for a two‐chambered system. The fuel cell utilizes bacteria Bacillus stratosphericus isolated from mangrove soil to generate bioenergy with an open‐circuit voltage of 0.3 V within 10 seconds. The fuel cell generates a maximum current density of 7 A m−2 and a power density of ∼ 150 mW m−2.

β-like FeOOH Nanoswords Activated by Ni Foam and Encapsulated by rGO toward High Current Densities, Durability, and Efficient Oxygen Evolution.

As an alternative to the oxygen evolution reaction (OER) electrocatalyst developed by a complex bi- or multimetal ion with layered double hydroxide (LDH) structures, we design a simple, self-supported, and single-metal-ion OER electrocatalyst having lower overpotentials and high current densities in alkaline water electrolyzers. Here, β-like FeOOH nanosword structures encapsulated by reduced graphene oxide (rGO) were cost-effectively synthesized on formable Ni foam substrates as an efficient and highly durable OER catalyst. It is revealed that the rGO uniformly covered the β-like FeOOH nanoswords to form a porous network achieving a lower overpotential of only 210 mV at 10 mA cm-2 with a stable operation for more than 40 h in alkali media. Moreover, a high current density of ∼300 mA cm-2 was achieved at less than 1.8 V. In-depth physical and electrochemical analysis indicated that the intrinsic charge transfer through activated Ni-foam, β-like phase, and nanosword morphology was evidently beneficial for enhancing the OER activity of the bare FeOOH, and its encapsulation by rGO further improved the conductivity and long-life durability. Our integrated OER electrocatalyst developed by a simple method (repeated soaking and quenching process) will aid in scaling up β-like FeOOH nanoswords for preparing uniform and large-area electrodes for industrial purposes.

Design and simulation of silicon detector cells with spiral ring electrode structures

Traditional pixel detectors are neatly arranged rectangular or square electrodes that cover almost the entire surface. Large electrode areas lead to high capacitance, and capacitance is the primary factor affecting detector noise. A large noise signal will reduce detector detection performance and the system S/N ratio. We have designed a spiral ring electrode silicon detector cell with n-type silicon bulk and systematically studied its electrical properties, including electric potential distribution, electric field distribution, electron concentration distribution, leakage current, full depletion voltage, and detector capacitance. It has been verified that the spiral ring electrode silicon detector has a smaller capacitance than the traditional detector and a smaller depletion voltage compared with the previously designed structures such as the inner circle broom-shaped structure. At the same time, high position resolution pixel detectors can be made by the array of these detector cells.

Mechanism and Optimized Process Conditions of Forming One-Dimensional ZnO Nanorods with Al-Doping by Electrodeposition Method

Textured transparent conductive electrodes for thin-film solar cells have been considered as an effective route for enhancing sunlight harvest due to light trapping. Here, we report a self-assembling electrochemical approach for preparing Al-doped ZnO nanorod arrays (NRAs) as light-trapping electrodes from a mixed aqueous solution of zinc nitrate and aluminium nitrate. The mechanism and optimized process conditions of forming one-dimensional ZnO nanorods with Al-doping were systematically investigated. The results showed that Al atoms were successfully doped into ZnO crystal lattice, and the morphologies could be controlled by adjusting the Al3+/Zn2+ ratio in the precursors and deposition time. The Al-doped ZnO films grew into well-aligned hexagonal NRAs with c-axis perpendicular to the substrates and then transited into a mixture of nanosheets and nanorods with Al3+/Zn2+ ratio increasing. They exhibited good electrical conductivity with a sheet resistance of 68-167Ω/square and appropriate visible light transmittance of 61-82%. Taking into account of desired morphology and phase purity, as well as good electrical conductivity and optical transmittance, the optimal window of Al3+/Zn2+ ratio in the precursors was determined between 1 at% and 2 at% with applied potential of -1.5V, bath temperature of 80°C, and deposition time of about 30min. The electrodeposition method provides a facile and efficient route for obtaining large-area textured transparent electrodes at a low cost.

Multi-walled vanadium oxide nanotubes modified 3D microporous bioderived carbon as novel electrodes for hybrid capacitive deionization

Herein, a promising rationally-designed, high surface area multi-walled vanadium oxide nanotubes (VOx NTs) with a large interlayer spacing (6.5 Å) has been demonstrated as a cathodic dopant for efficient hybrid capacitive deionization (c-HCDI). The VOx NTs enhanced the surface charge of the 3D microporous graphene-like carbon, derived from natural palm tree (CNPT), as verified by Raman profiles and potential of zero charge measurements. The CDI batch-fashion testing has been performed using large surface area electrodes (6 × 7 cm2) and 135 ml of saline NaCl electrolyte. Interestingly, the used c-HCDI showed high salt adsorption capacity (SAC) of 25.0 mg/g for 6 mM NaCl at 1.6 V compared to the symmetric capacitive deionization configuration (s-CDI) that is only sustaining 16.0 mg/g. Besides, the cell demonstrates efficient stable SAC regardless of the initial feed concentration (1.6–25 mM) of NaCl. The charge efficiency of the c-HCDI markedly raised by around 25% over s-CDI for 5 mM NaCl, indicating the improved permselective manner of sodium ion diffusion/intercalation at the VOx NTs/CNPT cathode. Most importantly, the c-HCDI demonstrates a superior salt adsorption retention of 94.7% after 50 successive charge/discharge cycles compared to s-CDI that showed a decline of 7% after only 15 cycles. The Improved surface charge and wettability together with the pseudocapacitive storage manner of the cathode composite illustrate the synergism obtained via the hybrid configuration..

Organism epidermis/plant-root inspired ultra-stable supercapacitor for large-scale wearable energy storage applications

Wearable energy storage system must maintain robust electrochemical performance under severe mechanical and chemical deformations. Here, we demonstrate wearable supercapacitor system assembled with electrodes composed of one-step carbonized plant epidermis and gelatin based hydrogel electrolyte which possesses high electrochemical performance and superior reliability under ambient condition. The carbonized mulberry paper (MP) was used as an electrode to achieve improved volumetric energy density as well as mechanical-chemical reliability (e.g. mechanical toughness and acid resistance). Rationally designed active materials composed of vertically grown WO 3 NRs and reduced graphene oxide (rGO) anchored on MP, were employed for developing organism epidermis based supercapacitor. Such electrode exhibits high volumetric energy and power densities of 30.28 mWh cm −3 and 7.67 W cm −3 , retaining the volumetric capacitance of 96.0% even after 110,000 charge-discharge cycles. As the final step, we employed the gelatin based electrolyte with high ionic conductivity to solve evaporation and leakage problems of conventional electrolytes. Organism epidermis based supercapacitor integrated with hydrogel electrolyte showed high electrochemical performance and long-term stability under ambient condition even after exposure to acid, demonstrating its gareat suitability as a large-scale wearable energy storage system. We demonstrate wearable supercapacitor system assembled with electrodes composed of one-step carbonized plant epidermis and gelatin based hydrogel electrolyte which possesses high electrochemical performance and superior reliability under ambient condition. Organism epidermis based supercapacitor integrated with hydrogel electrolyte showed high electrochemical performance and long-term stability under ambient condition even after exposure to acid, demonstrating its great suitability as a large-scale wearable energy storage system. • We maximized areal and volumetric electrochemical performance (energy & power densities) and mechanical/chemical toughness through carbonized mulberry paper integrated with reduced graphene oxide (rGO) layer. Mulberry fibers inherently show excellent mechanical flexibility and acid resistance, since they have lower portion of lignin cellulose (~40%) compared with conventional paper fiber. However, electrochemically inactive mulberry fiber exhibits still low areal/volumetric energy densities and electrochemical reliability. Thus, we used carbonized mulberry paper as a substrate and electrode in this study, which was maximized for volumetric energy/power densities and mechanical/chemical toughness. • We have designed the plant-root inspired active materials structure with excellent electrochemical reliability and performances. Inspired from plant-root, we synthesized active materials structure by one-step reduction heat treatment, where WO 3 nanorods (NRs) vertically grow within the spaces of rGO and are anchored as strongly as plant-root on the carbonized mulberry fibers. The anchored structure can effectively maintain electrochemical performance and flexibility of carbonized paper by preventing delamination of WO 3 NRs even without protection layer. WO 3 NRs anchored carbonized mulberry paper (thickness 110 µm) with rGO layer exhibits volumetric capacitance retention of 96% for 110,000 cycles. In addition, maximum volumetric energy and power densities were increased to 30.28 mWh cm −3 and 7.67 W cm −3 (improvement of 220%). • Conventional liquid and gel-type electrolyte have critical issues including evaporation under ambient condition and leakage under mechanical bending-twisting deformation. Such problems are main causes of rapid electrochemical performance degradation. In our work, gelatin based hydrogel electrolyte extracted from porcine skin was integrated with electrode, in order to fabricate wearable energy storage system that is capable of operating in ambient conditions. The gelatin based hydrogel electrolyte can retain water contents and high ionic conductivity under ambient condition over 2 weeks. Ionic conductivity maintained 90.3% (228 mS cm −1 ) after two weeks of exposure to ambient condition, and the moisture content was maintained 98.0%. • We further extended organism epidermis based supercapacitor to large-scale application capable of operation in ambient condition. High hydrophilicity of mulberry paper enables the uniform deposition of precursor material for growth of WO 3 , i.e, WO 3 precursor, that is dispersed in the aqueous solution. As a result, GO and WO 3 precursor were uniformly deposited on large-area electrode with 9, 25, 49 cm 2 followed by carbonization, resulting in the fabrication of large-scale organism epidermis based supercapacitor.

Plasmon-enhanced nanosoldering of silver nanoparticles for high-conductive nanowires electrodes

The silver nanowires (Ag NWs) electrodes, which consist of incompact Ag nanoparticles (NPs) formed by multi-photon photoreduction, usually have poor conductivities. An effective strategy for enhancing conductivity of the Ag NWs electrodes is plasmon-enhanced nanosoldering (PLNS) by laser irradiation. Here, plasmon-enhanced photothermal effect is used to locally solder Ag NPs and then aggregates of these NPs grow into large irregular particles in PLNS process. Finite element method (FEM) simulations indicate that the soldering process is triggered by localized surface plasmon-induced electric field enhancement at “hot-spots”. The effectiveness of PLNS for enhancing conductivity depends on laser power density and irradiation time. By optimizing the conditions of PLNS, the electrical conductivity of Ag NWs is significantly enhanced and the conductivity <em>σ</em>_s is increased to 2.45×10⁷ S/m, which is about 39% of the bulk Ag. This PLNS of Ag NWs provides an efficient and cost-effective technique to rapidly produce large-area metal nanowire electrodes and capacitors with high conductivity, excellent uniformity, and good flexibility.

Regulated iron corrosion towards fabricating large-area self-supporting electrodes for an efficient oxygen evolution reaction

Regulated iron corrosion is used to prepare an oxygen evolution electrode with OER activity of affording a low overpotential of 291 mV to reach 500 mA cm−2 and long-term durability for 100 h. The corrosion mechanisms are studied systematically.

Self-supported Cu3P nanowire electrode as an efficient electrocatalyst for the oxygen evolution reaction.

Hydrogen is an ideal energy carrier due to its abundant reserves and high energy density. Electrolyzing water is one of the carbon free technologies for hydrogen production, which is limited by the sluggish kinetics of the half reaction of the anode – the oxygen evolution reaction (OER). In this study, a self-supported Cu3P nanowire (Cu3P NWs/CF) electrode is prepared by electrodeposition of a Cu(OH)2 nanowire precursor on conductive Cu foam (Cu(OH)2 NWs/CF) with a subsequent phosphating procedure under a N2 atmosphere. When used as an OER working electrode in 1.0 M KOH solution at room temperature, Cu3P NWs/CF exhibits excellent catalytic performance with an overpotential of 327 mV that delivers a current density of 20 mA cm−2. Notably, it can run stably for 22 h at a current density of 20 mA cm−2 without obvious performance degradation. This highly efficient and stable OER catalytic performance is mainly attributed to the unique nanostructure and stable electrode construction. Interestingly, this synthesis strategy has been proved to be feasible to prepare large-area working electrodes (e.g. 40 cm−2) with unique nanowire structure. Therefore, this work has provided a good paradigm for the mass fabrication of self-supporting non-noble metal OER catalysts and effectively promoted the reaction kinetics of the anode of the electrolyzing water reaction.

Recent trends in graphene supercapacitors: from large area to microsupercapacitors

In this perspective, the recent trends in graphene supercapacitor research are shown, from the use of pseudocapacitor elements to enhance the performance of large-area electrodes, to its miniaturization driven by versatile fabrication techniques.

Features of Electromagnetic Field Excitation in a Capacitive HF Discharge. I. General Aspects. A Simple Model of Symmetric Discharge

Electrodynamic properties of a low-pressure (electron collision frequency much lower than the field frequency) capacitive high-frequency (HF) discharge with large-area electrodes maintained by an electromagnetic field with frequency higher than 13 MHz is studied analytically. The discharge is sustained by surface waves propagating along the plasma–space-charge sheath–metal interface. When describing the sheath, dispersion curves for even and odd surface waves in a three-layer structure (sheath–plasma–sheath) surrounded by metal boundaries are calculated within the framework of the matrix model. It is demonstrated that the field of the fundamental mode (the quasi-TEM mode) must be taken into account for correct discharge impedance calculation in the case of low electron densities, while the field of the surface wave must be taken into account in the case of high electron densities. An approximate expression governing the discharge impedance that is based on accounting only for one mode is derived. The expression is valid at low electron densities when the surface waves are absent, as well as high electron densities exceeding the value giving rise to a geometric resonance in the plasma–sheath system.

Highly Efficient Electrochemical Oxidation of Alcohols in a Flow Electrochemical Column Cell Modified with Au Nanoparticle Catalyst

Electrosynthesis is a powerful means for obtaining a variety of useful chemical products without employing toxic or otherwise hazardous chemical reagents and under relatively mild conditions. However, conventional batch-type cells suffer from a low productivity due to narrow two-dimensional reaction fields in the electrochemical system. To overcome this problem, we utilized continuous-flow column cell[1]. Although it was developed for a highly sensitive coulometric analysis of trace chemical substances in 1968, it is also expected to conduct rapid and quantitative bulk electrolysis due to its large electrode area and continuous-flow system. This flow cell consisted of a working electrode compartment and a counter electrode compartment, separated by an ion permeable Vycor® glass tube (Figure 1 (a)). A bundle of carbon fiber threads was tightly packed as a working electrode in the continuous-flow column cell, and a Pt spiral wire was used as a counter electrode. During several decades, the bulk gold has been considered as less active material, but at nanoscale, it exhibits surprisingly physicochemical and catalytic properties[2]. Therefore, in this work, the carbon fiber surface was also functionalized with Au nanoparticle catalyst to promote an electrochemical oxidation of alcohols.As a result, we have successfully demonstrated an efficient electrocatalytic oxidation of benzyl alcohol to provide benzaldehyde and benzoic acid with high current efficiencies in alkaline media. Moreover, it was also found that the selectivity of benzaldehyde was influenced by the added base amounts, and increased up to 97% by decreasing the amounts. We will also report the results of electrochemical oxidation of other alcohols.

Electrically compensated, tattoo-like electrodes for epidermal electrophysiology at scale.

Epidermal electrophysiology is widely carried out for disease diagnosis, performance monitoring, human-machine interaction, etc. Compared with thick, stiff, and irritating gel electrodes, emerging tattoo-like epidermal electrodes offer much better wearability and versatility. However, state-of-the-art tattoo-like electrodes are limited in size (e.g., centimeters) to perform electrophysiology at scale due to challenges including large-area fabrication, skin lamination, and electrical interference from long interconnects. Therefore, we report large-area, soft, breathable, substrate- and encapsulation-free electrodes designed into transformable filamentary serpentines that can be rapidly fabricated by cut-and-paste method. We propose a Cartan curve-inspired transfer process to minimize strain in the electrodes when laminated on nondevelopable skin surfaces. Unwanted signals picked up by the unencapsulated interconnects can be eliminated through a previously unexplored electrical compensation strategy. These tattoo-like electrodes can comfortably cover the whole chest, forearm, or neck for applications such as multichannel electrocardiography, sign language recognition, prosthetic control or mapping of neck activities.

Large-area flexible nanostripe electrodes featuring plasmon hybridization engineering

Multifunctional flexible Au electrodes based on one-dimensional (1D) arrays of plasmonic gratings are nanofabricated over large areas with an engineered variant of laser interference lithography optimized for low-cost transparent templates. Au nanostripe (NS) arrays achieve sheet resistance in the order of 20 Ohm/square on large areas (∼ cm2) and are characterized by a strong and dichroic plasmonic response which can be easily tuned across the visible (VIS) to near-infrared (NIR) spectral range by tailoring their cross-sectional morphology. Stacking vertically a second nanostripe, separated by a nanometer scale dielectric gap, we form near-field coupled Au/SiO2/Au dimers which feature hybridization of their localized plasmon resonances, strong local field-enhancements and a redshift of the resonance towards the NIR range. The possibility to combine excellent transport properties and optical transparency on the same plasmonic metasurface template is appealing in applications where low-energy photon management is mandatory like e.g., in plasmon enhanced spectroscopies or in photon harvesting for ultrathin photovoltaic devices. The remarkable lateral order of the plasmonic NS gratings provides an additional degree of freedom for tailoring the optical response of the multifunctional electrodes via the excitation of surface lattice resonances, a Fano-like coupling between the broad localised plasmonic resonances and the collective sharp Rayleigh modes.

A Novel High Q Lamé-Mode Bulk Resonator with Low Bias Voltage.

This work reports a novel silicon on insulator (SOI)-based high quality factor (Q factor) Lamé-mode bulk resonator which can be driven into vibration by a bias voltage as low as 3 V. A SOI-based fabrication process was developed to produce the resonators with 70 nm air gaps, which have a high resonance frequency of 51.3 MHz and high Q factors over 8000 in air and over 30,000 in vacuum. The high Q values, nano-scale air gaps, and large electrode area greatly improve the capacitive transduction efficiency, which decreases the bias voltage for the high-stiffness bulk mode resonators with high Q. The resonator showed the nonlinear behavior. The proposed resonator can be applied to construct a wireless communication system with low power consumption and integrated circuit (IC) integration.