Thin Electrodes Research Articles

Synthesis, characterization, and implementation of BaNiO3 perovskite nanoparticles as thin film supercapacitor electrode

AbstractThis work is the first attempt to explore the supercapacitor applications of Barium nickelate (BaNiO3) perovskite nanoparticles. The nanoparticles are synthesized using a simple combustion method and their morphology, elemental composition, and so forth are studied using standard characterization methods such as x‐ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and so forth. The nanoparticles were found to be hexagonal in shape, with an average particle size of 16 nm, and the elemental analysis confirms the successful synthesis of the BaNiO3 perovskite nanoparticles. For electrochemical studies, the electrodes are fabricated over a wearable and flexible conductive fabric (CF) substrate. A slurry paste of the synthesized BaNiO3 nanoparticles is applied over CF and dried overnight, thereby forming a thin film electrode. The fabricated electrode acts as a positive electrode with a high specific capacitance of 508.64 F g−1 at 2.2 A g−1 current density. Upon increasing the current density, the electrode maintains 60% of its specific capacitance and displays 97% cyclic stability over 5000 cycles. The electrochemical impedance spectroscopy (EIS) study indicates excellent conductivity of the electrode, with a bulk resistance of 3.2 Ohms. The electrochemical performance of the fabricated electrode is also compared with various previously reported works and the electrode displays higher specific capacitance and better cyclic stability. These findings suggest that the BaNiO3 perovskite nanoparticles‐based electrode holds promise for utilization as an anode material in supercapacitor applications.

Layer-by-layer assembling redox wood electrodes for efficient energy storage

The exploration of redox-active organic materials and low tortuous thick-electrodes is attractive for energy storage. The in-situ valorized lignin on raw wood surface accompanied by layer-by-layer deposition of electro-active materials endow such spatially distributed wood electrodes with high specific capacitance. Here, we report a layer-by-layer assembled ca.1.5 mm-thick redox wood hybrid electrode with 20 mg cm-2 electro-active mass loading for efficient energy storage. The in-situ modified surface lignin in treated wood (TrW) holds promise as redox-active material with enriched nanoporosity, carbonyl functionalities, and multi-phase ionic transport structure. The carbon nanotubes (CNTs) networking with in-situ polymerized polypyrrole (PPy) nanorods three-dimensionally in the lumen of TrW afford a wool-like, highly porous nanostructure. Such a hierarchical structured PPy@CNTs@TrW electrode offers a high areal capacitance of 1.46 F cm-2 with an extraordinary energy density of 0.983 mWh cm-3 (3.68 Wh kg-1) and power density of 5.4 mW cm-3 (20.25 W kg-1). Here, the valorized surface lignin contributes contributes to electrochemical energy storage accompanied by spatially distributed PPy@CNTs in low tortuous electrodes. The electrode offers extremely low electrochemical impedance of 0.61 Ω electrode resistance and 1.57 Ω electrolyte resistance. The hybrid wood electrode showcases even higher conductivity and energy/power density than thin carbonized wood and other state-of-the-art thin electrodes made of highly conductive three-dimensional networks. This work highlights the potential of in-situ valorized lignin in developing high-performance eco-friendly thick-electrodes for electrochemical energy storage applications.

Fabrication of microfluidic pH sensing chip based on sputtered Sb2O3/Sb thin film working electrode and AgIO3/Ag thin film reference electrode for detection of A549 cells

In this study, we present the fabrication and characterization of a microfluidic pH sensing chip designed to detect human lung cancer (A549) cells. The chip utilizes a Sb2O3/Sb thin film as the working electrode and an AgIO3/Ag thin film as the reference electrode, both deposited using the radio frequency (RF) sputtering technique. The PDMS microfluidic channel was prepared using a 3D-printed mold, followed by curing of PDMS within the mold. The fabricated sensing chip demonstrated excellent linear response (R2 ∼ 0.99) and appreciable Nernstian sensitivity (average = -57.02 ± 1.23 mV/pH, n = 4) in a wide pH range of 1.68–10.01. It exhibited good stability over a 48-hour duration with acceptable drift voltage and negligible temperature impact on the sensing performance. Further, in-vitro pH testing of human lung cancer (A549) cells was performed to investigate the real-time pH measurement ability of the developed microfluidic pH sensing chip.

Functionalized interfacial cover design toward pure silicon anode for high power density lithium–ion capacitor

A lithium–ion capacitor, comprising a capacitor–type cathode and battery–type anode, exhibits high power and energy density; however, the integration of different charge storage mechanisms in one cell naturally leads to a kinetic mismatch between the two electrodes, reducing the power density and cycle stability. To solve this problem, high–capacity anode materials with thinner electrodes are required. Silicon, with its high specific capacity, is considered a promising anode material with high energy and power density; however, pure Si anodes undergo rapid capacity fading and exhibit increased internal resistance owing to volume changes during cycling. In this study, both sides of the electrode are covered with functional layers consisting of functionalized herringbone–type carbon nanofibers to protect the Si electrode from degradation. The polar functional groups on the nanofibers weakly interact with the native oxide layer of the Si surface and the carboxyl groups of the binder, ensuring stable contact between electrode materials over repeated cycles. Moreover, the conductive functional cover promotes uniform lithium ion fluxes, aiding the formation of a stable solid electrolyte interphase layer. This study investigates the effects of this strategy on pure Si electrodes by surface morphology analysis, assessment of chemical interactions, and electrochemical testing. This approach has the potential to overcome the degradation of Si electrodes and significantly improve the power and energy density of lithium–ion capacitors.

Tuning the electrochemical performance of graphite electrodes in lithium-ion batteries: Thermodynamics versus kinetics

Improving the energy density of lithium-ion batteries is a goal pursued in state-of-the-art batteries, and the use of thick electrodes is one of the most direct and effective methods. However, thick electrodes are often accompanied by severe deterioration in electrochemical performance. Graphite is a widely used anode material and great efforts are made from kinetic parameters to improve the performance of thick electrodes, while the thermodynamic effects are ignored for a long time. Herein, this work focuses on elucidating the thermodynamic effects on electrode processes and revealing regulatory effects of the equilibrium potential on reaction. Kinetics can cause electrodes to react nonuniformly, while thermodynamics can rectify electrodes reacting nonuniformly, leading to fluctuations in the reaction rate. The competitive relationship between kinetics and thermodynamics is explored in detail. The results demonstrate that the electrode process is still dominated by thermodynamics at high rates for thin graphite electrodes, while thick graphite electrodes quickly tend to be dominated by kinetics as the rate increases. Finally, a favorable performance enhancement can be obtained by optimizing the thermodynamic properties of graphite. This work illustrates that the alleviation of kinetic constraints is limited, providing a completely new guideline for future electrode design of lithium-ion batteries.

Direct electrochemical reduction of graphene oxide thin film for aptamer-based selective and highly sensitive detection of matrix metalloproteinase 2

Simple and low-cost biosensing solutions are suitable for point-of-care applications aiming to overcome the gap between scientific concepts and technological production. To compete with sensitivity and selectivity of golden standards, such as liquid chromatography, the functionalization of biosensors is continuously optimized to enhance the signal and improve their performance, often leading to complex chemical assay development. In this research, the efforts are made on optimizing the methodology for electrochemical reduction of graphene oxide to produce thin film-modified gold electrodes. Under the employed specific conditions, 20 cycles of cyclic voltammetry (CV) are shown to be optimal for superior electrical activation of graphene oxide into electrochemically reduced graphene oxide (ERGO). This platform is further used to develop a matrix metalloproteinase 2 (MMP-2) biosensor, where specific anti-MMP2 aptamers are utilized as a biorecognition element. MMP-2 is a protein which is typically overexpressed in tumor tissues, with important roles in tumor invasion, metastasis as well as in tumor angiogenesis. Based on impedimetric measurements, we were able to detect as low as 3.32 pg mL−1 of MMP-2 in PBS with a dynamic range of 10 pg mL−1 – 10 ng mL−1. Further experiments with real blood samples revealed a promising potential of the developed sensor for direct measurement of MMP-2 in complex media. High specificity of detection is demonstrated – even to the closely related enzyme MMP-9. Finally, the potential of reuse was demonstrated by signal restoration after experimental detection of MMP-2.

Sensitivity of chitosan/reduced graphene oxide/manganese dioxide modified electrodes for cholesterol detection using cyclic voltammetry

Cholesterol detection needs to be carried out to detect early symptoms of dangerous diseases such as heart disease. The process of detecting cholesterol in the human blood requires a sensitive detection tool in order to produce accurate values. This paper reports the performance of chitosan thin films modified with reduced graphene oxide (rGO) and manganese dioxide (MnO2) as the sensitive layer of working electrodes in detecting cholesterol. The electrode substrate is a copper-screen printed electrode (copper-SPE) which was patterned into 5 mm of sensitive area. The chitosan and chitosan-reduced graphene oxide (rGO) matrices were deposited on the top of working electrodes. The characterization of chitosan, chitosan/rGO, and chitosan/rGO/MnO2 thin films was performed using AFM, FE-SEM, and FTIR. The electrochemical sensing properties of modified working electrode were observed using an electrochemical method of cyclic voltammetry (CV). The novelty of this research is the utilization of chitosan/rGO/MnO2 thin film-based working electrode for detecting cholesterol. The testing results indicated that the sensitivity of the modified working electrodes increased when working electrodes based on chitosan/rGO/MnO2 thin film were used for cholesterol detection compared to the working electrodes based on the chitosan thin film. It was proven from the sensitivity of working electrodes based on chitosan/rGO/MnO2 thin film which gave the lowest value of 3.21 × 10−5 µA/µM as well as the ability of working electrodes based on chitosan/rGO/MnO2 thin film which worked at limit of detection (LoD) 0.26 µM/L and limit of quantification (LoQ) 0.87 µM/L. Based on the sensitivity, LoD, and LoQ values, the chitosan/rGO/MnO2 modified electrodes can be used as working electrodes to measure cholesterol concentration in blood.

The readout panels for the BI-RPC project for ATLAS Phase-II upgrade

To take full advantage from the LHC upgrade to high luminosity in 2029, the ATLAS community has approved an intensive detector upgrade program that includes the construction of an additional trigger layer positioned close to the BI MDT chambers of the muon spectrometer. These chambers are RPC with thin gas gap, thin High Pressure Laminate electrodes coated with graphite on one side, and only use strips orthogonal to the beam-axis to reconstruct the eta and phi coordinates of the detector point where an ionizing particle passes. A detailed description of the construction and validation of these strip panels in China and Italy assembly sites, is presented here.

Ultrasonic non-destructive evaluation study of molecular diffusion bonding of thin copper-aluminum electrode sheets

The weld quality of copper and aluminum thin electrode sheets in molecular diffusion bonding was non-destructively evaluated using ultrasonic resonance techniques. During the welding process, the intermediate layer material nickel diffuses into the molecules of both the copper sheet and aluminum sheet, resulting in the formation of a solid solution phase layer. This leads to a 5-layer structure in the welded body. If there are defects in this solid solution phase layer, it can cause mutations in the ultrasonic resonance signals within the weld body. In order to characterize the weld quality between copper and aluminum sheets, an acoustic attenuation coefficient was introduced. The ultrasonic resonance signals within the weld body of copper and aluminum thin electrode sheets were analyzed under four different welding states. Experimental testing revealed significant differences in acoustic attenuation coefficients among these different welding states. A smaller acoustic attenuation coefficient indicates better welding quality. Therefore, by setting a reasonable threshold for this coefficient, it is possible to effectively evaluate the welding quality of molecular diffusion bonding between copper and aluminum thin electrode sheets.

Design of Compact Multiple-test Machine for Evaluation of Electrical and Mechanical Properties of Flexible Thin Electrode

Design of Compact Multiple-test Machine for Evaluation of Electrical and Mechanical Properties of Flexible Thin Electrode

Investigation of interfacial thermal resistance between Bi2Te3 thin films and metal electrodes via TDTR

A challenge on promoting thermoelectric application is the low energy conversion efficiency of thermoelectric devices. Reducing the contact thermal resistance of a thermoelectric device can improve efficiency effectively. However, study on interfacial thermal transport is lack due to the difficulty on contact thermal resistance measurement. Herein, a study on contact thermal resistance between thermoelectric and electrode materials was reported. We prepared various heterostructures of Bi2Te3–Cu and Bi2Te3–Ni via magnetron sputtering, and measured the contact thermal resistance using a time-domain thermoreflectance technique. Our results show that the contact thermal resistance is affected by both chemical and physical properties of interface. The chemical and physical stability of interfaces, the surface roughness and porosity of films, as well as electrical properties of Bi2Te3, are all related to the contact thermal resistance. The contact thermal resistance of Bi2Te3–Ni prepared at 400 °C can be reduced to 3.96 × 10−7 m2KW−1. Our work provides important experimental data and theoretical basis for optimizing the interlayer between thermoelectric materials and electrodes, and improving energy conversion efficiency of thermoelectric devices.

Full-epitaxial ScAlN and MgZnO solidly mounted resonators based on epitaxial acoustic Bragg reflector

A full-epitaxial bulk acoustic wave (BAW) resonator is attractive because of its high Q and high-power handling capability. An epitaxial technique is difficult to be employed due to the amorphous SiO2 low acoustic impedance layer in the solidly mounted resonator (SMR), which consists of a piezoelectric thin film on an acoustic Bragg reflector. In this study, we report a full-epitaxial ScAlN or MgZnO SMR based on an epitaxial Ti/Pt or ZnO/Pt acoustic Bragg reflector. The pole figure of epitaxial ScAlN and MgZnO piezoelectric layers showed clear sixfold symmetry. The epitaxial Sc0.43Al0.57N SMR exhibits keff2 of 13.6%. Moreover, the full-epitaxial metal Bragg reflector can act as a thick bottom electrode. This thick electrode is attractive for high frequency operation above 10 GHz in which BAW filter suffers from Q degradation due to the increase in the resistivity of extremely thin electrode.

Development of an ultra-thin electrode for the oxygen evolution reaction in proton exchange membrane water electrolyzers

Noble metal electrocatalysts are highly preferred for the oxygen evolution reaction (OER) in a proton exchange membrane water electrolysis cell (PEMWE) due to their exceptional catalytic activity and stability. This study proposes a novel thin electrode (NTE) design to enhance the performance of noble metal electrocatalysts for the OER in PEMWE. The NTE utilizes a thin porous transport layer for the direct deposition of Iridium (Ir). Unlike conventional gas diffusion electrodes with deep porous structures that underutilize the catalyst due to limited triple-phase boundary conditions, the flat NTEs with straight-through pores overcome this restriction. The paper compares two deposition methods, electroplating and sputter coating. The in-situ electrochemical properties of NTEs with varying Ir loadings (0.06–1.01 mg cm−2) are investigated. The electroplated NTE demonstrates excellent mass activity, achieving 5.05 A mg−1 at 1.6 V and 80 °C. The NTE exhibits a simple fabrication process and low cost while significantly improving catalyst mass activity. Additionally, the NTE reduces electrode thickness from hundreds of micrometers to only 25 μm. This concept holds great promise for the future advancement of compact and high-efficiency PEMWE electrodes, resulting in reduced cost, volume, and mass of both the electrode itself and the overall system.

Evaluating 3D printed mesh geometries in ceramic LiB electrodes

Additive manufacturing techniques have the potential to promote a paradigmatic change in the electrode fabrication processes for lithium-ion batteries (LiBs) as they may offer alternative component designs to boost their performance or to customise the application. The present research work explores the use of low-cost fused filament fabrication (FFF) 3D printing to fabricate Li4Ti5O12 (LTO) mesh electrodes in the search for enlarged electrochemically active areas. Using different nozzle diameters (ND), we have 3D printed several mesh electrodes that after sintering allow an increase in the surface to volume ratio by up to ≈290% compared to conventional flat cylindrical geometries. As the conventional route to produce 3D printed meshes, i.e. stacking of consecutive layers with a 90° rotation, leads to problems of vertical misalignment that may affect the electrical contact, we have developed a new compact design that maximises the contact between layers. All the 3D printed mesh electrodes with thicknesses of 400 and 800 μm, exhibit electrochemical performance very close to those of thin (70 μm) electrodes, e.g. 175 mAh g−1 at C/2 in the case of ND = 100 μm, which is the theoretical capacity value for LTO. At higher C-rates, 800 μm-thick mesh electrodes with larger ND exhibit a marked drop in the reversible capacity (28 mAh g−1 at 8 C), although the values obtained improve notably those of the equivalent thick solid electrode (almost null at 8 C). The compact design demonstrated superior performance at high C-rates, improving by ≈70% the results of the best conventional mesh electrode at 8 C for 800 μm electrodes. These results highlight the potential of FFF-3D printing to generate novel high aspect ratio geometries and the impact of design and printing parameters on the performance of LiB electrode materials. Exploring alternative efficient geometries may facilitate the integration of thick electrodes in high energy density LiBs.

The Utilization of Candlenut Shell-Based Activated Charcoal as the Electrode of Capacitive Deionization (CDI) for Seawater Desalination

Activated carbon or activated charcoal is one of the best materials that can be used as a constituent of CDI electrodes, not only because of its various advantageous properties but also because it can be sourced abundantly from plant waste. This research aims to determine the effect of the thickness of the candlenut shell activated charcoal electrode and the particle size of the activated carbon used on the capacitive deionization (CDI) performance in seawater desalination. Candlenut shell-based activated charcoal is obtained in three stages, namely preparation, carbonization, and activation. The carbonization stage was done by using a pyrolysis reactor at a temperature of 400°C for 8 hours. The activation was done with the activator of H3PO4 67%. The variation of thickness was 6 mm, 8 mm, 10 mm, and 15 mm while the variation of particle size was 60 mesh, 80 mesh, 100 mesh, and 200 mesh. The results showed that the higher capacitance was obtained with the thinner electrodes, where the best value was the thinnest electrode, 6 mm, which produced the highest capacitance, 122.96 nF. For the desalination of seawater, it is shown that the finest particle/smallest particle size will result in the best desalination performance, where 200 mesh particle size will result in the decrease of salinity from 34% to 4%. That is 88.23% decrease in salinity. Therefore, the using of candlenut shell-based activated carbon as the electrode in CDI is proven to be able to obtain good performance in seawater desalination.

Morphology-correlated optical dispersion and pseudocapacitive charge storage of α-MnO2 electrodes towards simultaneous enhancement of optical transparency and areal capacitance

Herein, we presented the fabrication of α-MnO2 thin film pseudocapacitive electrodes with enhanced optical transparency and areal capacitance. The optimized electrodes were achieved through a low-energy, binder-free, hexamethylenetetramine-assisted electrodeposition. Before this, attempts to increase the optical transparency of MnO2 electrodes had only been successful by reducing its mass load and thickness, which compromised its storage capacity. In this study, analysis of the optical dispersion properties of MnO2 was combined with the electrochemical investigation to demonstrate a nexus between nano-morphology, transparency and storage capacity.

Numerical Evaluation of the Frequency-Dependent Impedance of Hemispherical Ground Electrodes through Finite Element Analysis

Metallic electrodes are widely used in many applications, the analysis of their frequency-domain behavior is an important subject, particularly in applications related to earthing/grounding systems, from dc up into the MHz range. In this paper, a numerical evaluation of the frequency-dependent complex impedance of the hemispherical ground electrode is implemented. A closed-form solution for non-zero frequencies is still a difficult task to achieve as evidenced in a previous paper dedicated to the subject and, therefore, numerical approaches should be an alternative option. The aim of this article is to present a solution based on a numerical method using finite element analysis. In typical commercial FE tools, electric currents exhibit azimuthal orientation and, as such, the magnetic field has a null azimuthal component but non-null axial and radial components. On the contrary, a dual problem is considered in this work, with a purely azimuthal magnetic field. To overcome the difficulty of directly using a commercial FE tool, a novel formulation is developed. An innovative 2D formulation, the ι-form, is developed as a modification of the H-formulation applied to axisymmetric magnetic field problems. The results are validated using a classical 3D H-formulation; comparisons showed very good agreement. The electrode complex impedance is analyzed considering two different cases. Firstly, the grounding system is constituted by a hemispherical electrode surrounded by a remote concentric electrode; in the second case, the grounding system is constituted by two identical thin hemispherical electrodes. Computed results are presented and discussed, showing how the grounding impedance depends on the frequency and, also, on the radius of the remote concentric electrode (first case) or on the distance between the two hemispherical electrodes (second case).

Enhancing the sensitivity of polymeric membrane polycation-sensitive electrodes by surface modification of a polydopamine nanolayer

In this work, a potentiometric polyion sensing strategy based on the surface layer-enhanced transmembrane ion transfer is demonstrated. A polydopamine (PDA) nanolayer with negative charges is modified onto the surface of the polycation-sensitive electrode membrane and used to increase the ion fluxes from the sample phase to the membrane phase. Such modification can significantly improve the detection sensitivity of potentiometric polyion sensors through electrostatic interactions between the cationic targets and anionic PDA groups, which can effectively promote the accumulation of the targets in the boundary layer of the organic membrane phase. By using a thin membrane protamine-sensitive electrode as a model, the detection sensitivity of the PDA-coated electrode (55 mV/μg·mL−1) is nearly five times higher than that of the unmodified electrode (12 mV/μg·mL−1). Moreover, the proposed surface PDA-modified polyion sensor can also be utilized as a general tool for sensitive detection of other polycationic targets and polyanionic species (e.g., the new cancer biomarker cell-free DNA). The proposed potentiometric sensing platform based on surface enhancement of ion transfer offers great potential for sensitive detection of various polyionic targets.

Sputtered vanadium carbon nitride (VCN) thin films: a potential electrode for supercapacitors

The preparation of efficient thin film-based electrode materials is a vital prerequisite for practical energy storage devices. Herein, we have prepared unique vanadium carbon nitride (VCN) thin films on FTO substrates by pulsed DC magnetron sputtering technique for competent supercapacitor electrodes. XRD analysis confirmed the crystalline nature of VCN thin films. SEM and AFM revealed a smooth morphology with an average grain size of 30 nm. Raman spectra showed two broad peaks around 1346 and 1589 cm−1, belonging to the D-band and G-band of VCN. The surface electronic states of VCN were investigated by XPS analysis, which confirmed the formation of pure VCN films without any impurities. The electrochemical performance of the thin film electrode was evaluated using cyclic voltammetry (CV), Galvanostatic charge–discharge (GCD), and Electrochemical impedance analysis (EIS). The electrochemical results showed the VCN thin films exhibited super capacitive behaviours. The maximum specific capacitance (Cs) value of 78.2 F g−1 was obtained from GCD studies. A variation in charge transfer resistance is detected from the EIS study, which arises due to the partial oxidation of the active nitride component. The VCN electrode showed good cycling stability, retaining 87% of its capacitance at a current density of 5 A g−1 even after 2000 cycles. The sputtered VCN films have been demonstrated as potential thin film electrodes for electrochemical supercapacitors for practical energy storage devices.

Hetero Acoustic Layer Surface Acoustic Wave Resonator Composed of LiNbO3 and Quartz.

In this work, a shear-horizontal (SH) mode surface acoustic wave (SAW) resonator based on LiNbO3 (LN)/Quartz (Qz) hetero acoustic layer (HAL) structure was studied by simulation and experiment. By this HAL structure, the displacement and electric displacement are well confined in the piezoelectric layer. A lower mechanical loss of Qz than that of lossy amorphous SiO2 further enhances the quality ( Q ) factor. In addition, a negative temperature coefficient of frequency (TCF) of LN is compensated by selecting the crystalline orientation of Qz with a positive TCF. According to simulation results, the Euler angles of (0°, 101°, and 0°) and the normalized thickness of 0.2-0.3 λ (wavelength) for LN are selected to obtain a higher impedance ratio ( Z -ratio) and bandwidth (BW). The Euler angles of (0°, 160°, and 90°) for Qz are selected to obtain the positive maximum TCF. The fabricated resonator exhibits a Z -ratio of 95 dB and a BW of 15.9% in the 700 MHz range. The fit figure of merit (FoM) reaches 410, which is the best level ever reported for an LN-based resonator. The TCF of the resonator is -77 ppm/°C at anti-resonance frequency. A group of resonators composed of LN and LN/Qz with thin and thick electrodes were fabricated to further illustrate the good performance of LN/Qz. The LN/Qz HAL SAW resonator demonstrated in this work exhibits a high Z -ratio, low TCF, and wideband, which has the potential for high-performance wideband filters with steep passband and good temperature characteristics.