Conductive Electrodes Research Articles

Impact of atomic layer deposition temperature on electrical and optical properties of ZnO:Al films

This work highlights the impact of growth temperature on the electrical and optical properties of Al-doped ZnO (AZO) films deposited by the atomic layer deposition (ALD) technique. The ALD process and super-cycle sequence have been optimized, identifying their influence on film resistivity. By using this optimum ALD procedure, the optical and electrical properties of AZO films have been widely analyzed considering the deposition temperature. Results show promising values with film resistivity in the range of 1 mΩcm and average optical absorption below 2% for 50 nm thick AZO layers. Hall effect, X-ray diffraction and ellipsometry measurements point out that these excellent values are related to their high carrier concentration and mobility, crystalline phase and optical band gap, resulting in ALD AZO films with excellent properties to be applied in photovoltaic devices as transparent conductive oxide electrode.

Pockels Effect of Interfacial Water on a Mono-Electrode Induced by Current Parallel to the Electrode Surface

When an electric field is applied between two electrodes facing each other immersed in a liquid, the interfacial Pockels effect, a refractive index change proportional to the electric field, occurs in the electric double layer at the liquid–electrode interface. Here, we report that the Pockels effect of interfacial water can be observed even when an electric field is applied parallel to the surface of a “single” electrode in an electrolyte solution. This is a non-trivial result since the electric field parallel to the interface should not cause a broken spatial inversion symmetry, which is required for the Pockels effect. The Pockels signal was detected as a change in the transmitted light intensity due to the field-induced spectral shift of the interference fringes of the transparent conductive oxide electrode layer on a glass substrate. The magnitude of the signal increased as it approached the ends of the electrode, and the sign reversed across the center of the electrode. The electric field distribution calculated from the interfacial potential difference due to the in-plane parallel current showed that an electric field perpendicular to the interface was induced, whose distribution was consistent with the position dependence of the Pockels signal. A similar phenomenon was also observed for a single copper electrode, confirming that this is a universal effect.

Unfolding the potassium storage mechanism of tin selenides

Tin selenides have attracted great attention as anode materials for alkali metal ion batteries in recent years because of the high theoretical capacity. However, there is currently few literatures on the application of tin selenides in potassium ion battery, and the comparative research on the actual potassium storage mechanism of different tin selenides is rarely reported. Herein, tin selenides including SnSe2@C and SnSe@C are synthesized by regulating the selenization temperature, and their potassium storage performance and the mechanism have been comparatively investigated with various physicochemical techniques as well as operando synchrotron X-ray diffraction (SXRD) and density functional theory (DFT) calculations. It is revealed that the better potassium storage performance of SnSe2@C is mainly due to the generation of highly conductive Se during the first depotassiation process, which not only participates in the subsequent potassiation/depotassiation process, but also improves the conductivity of electrode and facilitates the kinetics of K+. While the sluggish kinetics and partial irreversible decomposition of KxSe lead to the inferior potassium storage performance of SnSe@C.

Flexible, transparent and conductive wearable electronic skin based on 2D titanium carbide (MXene) ink

Flexible and transparent conductors are essentially required in epidermal wearable devices such as electronic-skins (E-skins) that facilitate human interaction and biofeedback. However, due to the “trade-off” effect between high electrical conductivity and optical transparency, it is difficult to obtain transparent E-skins with high electrical conductivity. Furthermore, traditional transparent conductor is bulky and brittle which is not suitable for flexible and wearable applications. Herein, ultrathin two-dimensional (2D) titanium carbide (MXene) nanosheets with metallic conductivity, hydrophilic surface and excellent mechanical flexibility was proposed as a novel high-performance transparent conductor, which was further developed as wearable E-skins. Solution-processable MXene conductive ink was obtained by facilely etching Al from MAX phase for large-scale spray coating to obtain flexible transparent conductors. The flexible, transparent, and conductive MXene-based electrodes own a sheet resistance as low as 200 Ω/sq, while with high optical transparency of 60% @550 nm, which is sufficient for the applications of E-skins. Moreover, the transparent MXene-based soft E-skins also exhibits outstanding mechanical flexibility which could maintain its high opto-electrical performance even after 1000 cyclic bending tests. In addition, the robust flexible transparent MXene-based E-skins also could accurately identify the movements of human body including approaching, touching and pressing, which is essentially required in various application scenarios such as human-machine interactions, touch panels and healthcare sensors. The solution-processable flexible, transparent and conductive MXene-based E-skins holds tremendous potential in emerging wearable applications.

Effects of Polydopamine Incorporation on the Nanostructure and Electrochemical Performance of Electrodeposited Polypyrrole Films

Polypyrrole films are commonly prepared as conductive electrode surfaces for a variety of applications. Recently, there has been increasing interest in improving the adhesive properties and biocompatibility of polypyrrole electrodes via the incorporation of bioinspired polydopamine within the polymer scaffold. However, very little is currently known about the structural effects of polydopamine incorporation during the electropolymerisation of hybrid films. In this work, we combine electrochemical quartz crystal microbalance studies, fundamental electrochemical characterisation, atomic force microscopy, and a suite of spectroscopic techniques in order to correlate changes in the structure and performance of polypyrrole–polydopamine films to the structural modifications of the nanostructure induced by polydopamine incorporation. The results indicate that polydopamine incorporation greatly increases the rate of hybrid film deposition, as well as improving adhesion, surface homogeneity, and wettability, with no compromise in charge transfer properties. Polydopamine incorporation is strongly suggested to occur in non-connected domains within a predominantly polypyrrole-like scaffold. We propose a two-step model of co-polymerisation and the subsequent surface adhesion of hybrid films. Results are expected to be of broad general interest to researchers utilizing polypyrrole and polydopamine to prepare tailor-made electrodes for biosensing and catalysis.

Monolithic Electrically‐Driven Retroreflector Based on Gold Nanoparticles Embedded in Ferroelectric Polymer

The surface plasmon resonance (SPR) observed in metal nanostructures finds application in biosensing, optical communication technologies, and neuromorphic computing. There it enables the detection and transduction of dielectric environment changes in the vicinity of the metal nanostructure. Combining this principle with materials where the dielectric environment can be electrically modulated, it becomes possible to realize active optoelectronic plasmonic devices specifically designed for optical communication technologies. In this work, the use of an organic ferroelectric polymer to reversibly modulate the localized SPR (LSPR) of gold nanoparticles (AuNPs) inducing a reversible spectral shift of the resonance is investigated. The proposed plasmonic modulator is based on a two‐terminal device composed of AuNPs deposited on a transparent conductive electrode, covered by a ferroelectric polymer poly(vinylidene fluoride‐co‐trifluoroethylene) with a metallic electrode on top also serving as the mirror. By applying a voltage bias between the two electrodes, an electric field is generated within the device, enabling precise control over the dielectric environment of the AuNPs and thereby modulating the LSPR. It is demonstrated that this concept can be easily fabricated, potentially flexible, lightweight, and robust, making it an attractive choice for optical communication devices, particularly as a free space modulating retroreflector.

Recent Advances in Stretchable and Permeable Electrodes for Epidermal Electronics

AbstractEpidermal electronics is an emerging wearable platform that involves attaching deformable forms of devices to the skin. Epidermal electrodes represent a vital component of this technology, as they provide a direct electronic interface with the skin for sensing and stimulation. However, most of the current electrodes are built on non‐permeable elastomer substrates, which can limit their long‐term, continuous operations in a non‐invasive manner. Fortunately, recent advancements in conductive materials and fabrication techniques have enabled high‐performance epidermal electrodes that are comfortable to wear. In order to track the latest progress, this review article first introduces the designs of permeable structures and the preparation of conductive electrodes. The subsequent discussion elaborates on effective strategies to achieve desirable properties, such as high conductivity, stretchability, skin adhesion, and biocompatibility. The emerging applications of permeable epidermal electrodes are also summarized. Finally, this review concludes with the current challenges and future directions of breathable epidermal electrodes.

Evolution of Metal Tellurides for Energy Storage/Conversion: From Synthesis to Applications.

Metal telluride (MTe)-based nanomaterials have emerged as a potential alternative for efficient, highly conductive, robust, and durable electrodes in energy storage/conversion applications. Significant progress in the material development of MTe-based electrodes is well-sought, from the synthesis of its nanostructures, integration of MTes with supporting materials, synthesis of their hybrid morphologies, and their implications in energy storage/conversion systems. Herein, an extensive exploration of the recent advancements and progress in MTes-based nanomaterials is reviewed. This review emphasizes elucidating the fundamental properties of MTes and providing a systematic compilation of its wet and dry synthesis methods. The applications of MTes are extensively summarized and discussed, particularly, in energy storage and conversion systems including batteries (Li-ion, Zn-ion, Li-S, Na-ion, K-ion), supercapacitor, hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and CO2 reduction. The review also emphasizes the future prospects and urgent challenges to be addressed in the development of MTes, providing knowledge for researchers in utilizing MTes in energy storage and conversion technologies.

Phosphorus-doped TiO2 mesoporous nanocrystals for anodes in high-current-rate lithium ion batteries

Limited by the intrinsic low electronic conductivity and inferior electrode kinetics, the use of TiO2 as an anode material for lithium ion batteries (LIBs) is hampered. Nanoscale surface-engineering strategies of morphology control and particle size reduction have been devoted to increase the lithium storage performances. It is found that the ultrafine nanocrystal with mesoporous framework plays a crucial role in achieving the excellent electrochemical performances due to the surface area effect. Herein, a promising anode material for LIBs consisting of phosphorus-doped TiO2 mesoporous nanocrystals (P-TMC) with ultrafine size of 2–8 nm and high specific surface area (234.164 m2 g–1) has been synthesized. It is formed through a hydrothermal process and NaBH4 assisted heat treatment for anatase defective TiO2 (TiO2–x) formation followed by a simple gas phosphorylation process in a low-cost reactor for P-doping. Due to the merits of the large specific surface area for providing more reaction sites for Li+ ions to increase the storage capacity and the presence of oxygen vacancies and P-doping for enhancing material’s electronic conductivity and diffusion coefficient of ions, the as-designed P-TMC can display improved electrochemical properties. As a LIB anode, it can deliver a high reversible discharge capacity of 187 mAh g–1 at 0.2 C and a good long cycling performance with ∼82.6% capacity retention (101 mAh g–1) after 2500 cycles at 10 C with an average capacity loss of only 0.007% per cycle. Impressively, even the current rate increases to 100 times of the original rate, a satisfactory capacity of 104 mAh g−1 can be delivered, displaying good rate capacity. These results suggest the P-TMC a viable choice for application as an anode material in LIB applications. Also, the strategy in this work can be easily extended to the design of other high-performance electrode materials with P-doping for energy storage.

Application and Parameter Optimization of Electro-Kinetic Geosynthetics Electrodes Based on the Wild Horse Optimizer in Horizontal Electric Field Sludge Dewatering

This study systematically compared the performance of five corrosion-resistant electrode materials for electro-dewatering. Through a comprehensive analysis of dewatering efficiency, energy consumption, and corrosion resistance, conductive plastic composite electrodes (EKG) were selected as the optimal electrode material for experimentation. Additionally, the impact of electric field strength and electrode spacing on the efficiency and energy consumption of electro-dewatering (EDW) was investigated. The results showed that the increase in electric field intensity could improve the solid content and dewatering efficiency of the sediments, but the corresponding energy consumption also increased. The increased spacing of the plates reduced the dehydration effect and increased the energy consumption. By employing the Wild Horse Optimization algorithm, empirical and multifactorial response models for the dewatering solidification process were established, aimed at predicting the dewatering performance and energy consumption. The study concludes that for the remediation of heavy metals, the electric field strength should not exceed 10 V/cm to avoid excessive heavy metal migration and potential adverse chemical reactions.

Ti3C2/Ni/Sm‐Based Screen‐Printed‐Electrode for the ECL Detection of Hydrogen Peroxide as a Milk Preservative

AbstractHydrogen peroxide is a widely used agent in the food industry for its sterilization, packaging, and transportation capabilities. However, its excessive concentration can lead to adverse health effects, especially in gastrointestinal conditions. As a result, it is crucial to detect its presence in food products, particularly milk. To address this need, we have developed a state‐of‐the‐art MXene‐based ECL system that can detect low‐concentration hydrogen peroxide levels with high sensitivity and accuracy. Our system incorporates 2D MXene structures, which not only enhance electrode conductivity but also form a complex with Ni/Sm‐LDH (layered double hydroxide) that enables detection across a broad linear range of 0.05–2 ppm in real samples. Furthermore, we have successfully lowered the detection limit to an impressive 0.005 ppm. With this innovative approach, we can ensure the safety and quality of food products, making it a significant breakthrough in the food industry.

From 0D to 3D: Hierarchical structured high-performance free-standing silicon anodes based on binder-induced topological network architecture

Free-standing silicon anodes with high proportion of active materials have aroused great attention; however, the mechanical stability and electrochemical performance are severely suppressed. Herein, to resolve the appeal issues, a free-standing anode with a “corrugated paper” shape on micro-scale and a topological crosslinking network on the submicron and nano-scale is designed. Essentially, an integrated three-dimensional electrode structure is constructed based on robust carbon nanotubes network with firmly anchored SiNPs via forming interlocking junctions. In which, the hierarchical interlocking structure is achieved by directional induction of the binder, which ensures well integration during cycling so that significantly enhances mechanical stability as well as electronic and ionic conductivity of electrodes. Benefiting from it, this anode exhibits outstanding performance under harsh service conditions including high Si loading, ultrahigh areal capacity (33.2 mA h cm−2), and high/low temperatures (−15–60 °C), which significantly extends its practical prospect. Furthermore, the optimization mechanism of this electrode is explored to verify the crack-healing and structure-integration maintaining along cycling via a unique self-stabilization process. Thus, from both the fundamental and engineering views, this strategy offers a promising path to produce high-performance free-standing electrodes for flexible device applications especially facing volume effect challenges.

Laser layered scanning strategy for fractal Ag mesh transparent conductive electrodes using selective laser ablation and its application to transparent heaters

In this study, 800 nm-thick silver (Ag) films were deposited on glass substrates via radio frequency (RF) magnetron sputtering. Based on a laser layered scanning strategy during selective laser ablation (SLA), periodic (1–4) and pattern-combined (4–9) fractal Ag mesh transparent conductive electrodes (TCEs) with two layered mesh thicknesses were prepared to investigate the influences of mesh thickness matching on their optical and electrical properties. The results revealed that constructing the layered mesh thickness by selectively removing the thick Ag layer could enhance the TCE optical transmittance without greatly sacrificing its electrical conductivity. The two kinds of fractal layered Ag mesh TCEs with mesh thickness matching of 800 nm: 500 nm were confirmed to have high performance uniformity, and respectively exhibited the highest figure of merit value of 16.03 × 10–2 Ω−1 and 15.23 × 10–2 Ω−1. Moreover, the best periodic (1–4) fractal layered Ag mesh TCE was adopted to fabricate a transparent heater (TH), which exhibited excellent heating performance (a maximum temperature of 143.1 ℃ with a response time of ∼ 80 s under a lower voltage of 1.3 V), switching cycle stability and deicing ability. The sheet resistance stability of the TH under different test conditions was also demonstrated. This work has a certain reference value for the preparation of high-performance TCEs and THs.

High‐Performance Fully Transparent Ultraviolet Photodetector Fabricated Using GaN‐Based Schottky Barrier Photodiode

Transparent electronics is a burgeoning field with exciting potential for next‐generation “see‐through” devices. The creation of high‐performance fully transparent ultraviolet photodetectors (PDs) is essential for enabling wearable and portable applications. In this study, metal–semiconductor–metal (MSM) type Al‐doped ZnO (AZO)/GaN/AZO and indium tin oxide (ITO)/GaN/ITO‐transparent ultraviolet PDs, are initially designed, utilizing AZO‐ and ITO‐transparent conductive electrodes. In these investigations, it is revealed that AZO and ITO form Ohmic and Schottky contacts, respectively, with GaN. Subsequently, building on these findings, a fully transparent Schottky barrier photodiode (SBPD) is developed for ultraviolet photodetection using AZO/GaN/ITO. The SBPD displays a high responsivity (R) of 1.41 × 103 A W−1, a detectivity (D*) of 6.85 × 1014 Jones, and a photo‐to‐dark current ratio exceeding 1 × 104 at a − 5 V bias. Furthermore, the SBPD demonstrates an ultrahigh responsivity of 1.18 A W−1 at 0 V bias, indicating its potential as a self‐powered device under extreme conditions. In these results, the tremendous potential of the high‐performance and fully transparent GaN‐based SBPD is demonstrated for environmental monitoring, optical communication, military radar, and other fields.

Fabrication of composite transparent conductive electrodes based on silver nanowires

Composite transparent conductive electrodes (C-TCEs) have recently been produced using low-cost techniques to keep up with the boom in the fabrication and development of optoelectronic devices. In this article, silver nanowires (AgNWs) were successfully synthesized by a simple hydrothermal method using different molecular weights MWs of poly (N-vinylpyrrolidone) (PVP). Graphene oxide (GO) was prepared using the modified Hummers’ method and a reduction step was held on GO films to produce reduced GO (rGO). C-TCEs were fabricated by over-coating the AgNWs electrodes with rGO, or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate to improve the roughness, surface energy, and sheet resistance. The influence of using lower and higher MWs of PVP on the yield, shape, and size of AgNWs was investigated. The results showed that using lower MW of PVP had a great effect on the yield, morphology, and aspect ratio of AgNWs with diameter of 46 nm and average length 12 µm. The optical, morphological, topographical, and electrical properties of TCEs were studied. AgNWs/rGO composite electrode provided the lowest surface roughness and surface energy of 250 nm and 47.95 mN/m, respectively, with a relatively high transparency of 78.2% at 550 nm light wavelength, and a low sheet resistance of 27 Ω/□.

Application of Carbon Materials in Conductive Electrodes for Perovskite Solar Cells

Over the past decade, perovskite solar cells (PSCs) have achieved significant achievements. But the golden triangle problem of commercial development, which encompasses high efficiency, high stability, and low cost, remains unresolved. Carbon materials exhibit a diverse range of morphological structures and possess numerous advantages. They are extensively used in PSCs to overcome the challenges encountered during PSCs commercialization. The PSCs utilizing graphene as the top electrodes not only deliver an impressive efficiency of 22.8%, but also show exceptional long‐term stability. The PSCs using carbon nanotubes as transparent conductive electrodes obtain an efficiency of 19%, exhibiting significant potential for scalable applications. Herein, the advantages of carbon materials as conductive electrodes are overviewed. The compatibility of carbon materials as conductive electrodes in PSCs, along with the associated challenges, regulatory strategies, and device performance are systematically discussed in terms of their intrinsic characteristics. The application of carbon materials derived from petroleum by‐products and biomass in the top electrodes of PSCs are summarized in detail. Finally, the underlying reasons why PSCs using carbon electrode show a comparatively lower efficiency when compared to conventional devices is analyzed in‐depth. The potential research directions are proposed to promote the development of carbon conductive electrodes in PSCs.

Hydroxyapatite-Gold Modified Screen-Printed Carbon Electrode for Selective SARS-CoV-2 Antibody Immunosensor.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), or coronavirus disease 2019 (COVID-19), is still spreading worldwide; therefore, the need for rapid and accurate detection methods remains relevant to maintain the spread of this infectious disease. Electrochemical immunosensors are an alternative method for the rapid detection of the SARS-CoV-2 virus. Herein, we report the development of a screen-printed carbon electrode immunosensor using a hydroxyapatite-gold nanocomposite (SPCE/HA-Au) directly spray-coated with the immobilization receptor binding domain (RBD) Spike to increase the conductivity and surface electrode area. The HA-Au composite synthesis was optimized using the Box-Behnken method, and the resulting composite was characterized by UV-vis spectrophotometry, TEM-EDX, and XRD analysis. The specific interaction of RBD Spike with immunoglobulin G (IgG) antibodies was evaluated by differential pulse voltammetry and electrochemical impedance spectroscopy methods in a [Fe(CN)6]4-/3- solution redox system. The IgG was detected with a detection limit of 0.0561 pg mL-1, and the immunosensor had selectivity and stability of 103-122% and was stable until week 7 with the influence of storage conditions. Also, the immunosensor was tested using real samples from human serum, where the results were confirmed using the chemiluminescent microparticle immunoassay (CMIA) method and showed satisfactory results. Therefore, the developed electrochemical immunosensor can rapidly and accurately detect SARS-CoV-2 antibodies.

Performance evaluation of aluminum nitride-decorated AgNWs-based transparent conductive electrodes deposited on flexible substrates

Performance evaluation of aluminum nitride-decorated AgNWs-based transparent conductive electrodes deposited on flexible substrates

Deep Multiphase Conversion Derived from NiTe2 Nanosheets with Preferred Kinetics for Highly Reversible Mild Aqueous Zinc–Tellurium Batteries

AbstractConversion‐type tellurium‐based cathodes have attracted great attention in aqueous zinc‐ion batteries (AZIBs) due to potentially high capacity with impressive Te4+/Te0/Te2− conversion. However, impeded by the low‐conductivity Te4+ species and unpreferred kinetics, realizing deep zinc‐tellurium redox remains a major challenge. Herein, energetic NiTe2 nanosheets are first proposed and implemented as preprepared tellurium‐based deep redox cathodes in AZIBs with accelerated electron transport and favorable kinetics. Operando synchrotron X‐ray diffraction and comprehensive ex situ characterizations demonstrate that Te4+ species from direct oxidation of NiTe2 in dilute mild‐aqueous electrolyte undergo a thermodynamic two‐step TeO2→Te→ZnTe discharge process, while the intertwined tellurium oxides and high‐conductivity nickel monomers derived in situ from NiTe2 nanosheets promote a kinetics‐preferred one‐step ZnTe→TeO2 charging conversion with significantly boosted reversibility. Therefore, a high capacity of 510 mAh g−1 at 50 mA g−1 and 93% capacity retention over 400 cycles at 2000 mA g−1 are established. Operando pH tracking and electrode‐electrolyte engineering analyses define that the mild electrolyte environment rich in moisture and electrode conductivity optimization are both critical for achieving reversible tellurium deep redox conversion.

First-principles study of slag impurity doped Na2Ti3O7 as anode material for Na-ion batteries

Na2Ti3O7 (NTO) has attracted significant attention as a promising anode material for sodium-ion batteries (SIBs). However, its practical electrochemical performance is hindered by its inherently low electronic conductivity. To address this limitation, researchers have turned to elemental doping as an effective strategy to enhance the conductivity of NTO electrodes. Interestingly, the process of purifying titanium for NTO synthesis often yields Al and Ca impurities, which can be harnessed as cost-effective dopants. In this study, we employ first-principles calculations to conduct a comprehensive investigation into the structural, electronic, and sodium ion diffusion properties of NTO when doped with Al and Ca, either individually or in combination. Doping system structure has good stability. Our findings reveal that both Al or Ca single-doping Our findings reveal that all the Al and Ca single-doping, and AlCa co-doping transform NTO from semiconducting into metallicity. Notably, the sodium ion migration barriers for Ca single-doping greatly decrease (0.13 eV) compared with that of pristine NTO (0.23 eV), indicating fast ion transport. The insights gained from our research hold promise for the development of cost-effective multi-component anode materials for SIBs.