Electrode Surface Research Articles

On-Site Nanowire Growth of Peptides Enables Stable Amine Selective QCM Gas Sensing.

Here, we demonstrate a novel methodology for developing stable quartz crystal microbalance (QCM) gas sensors tightly decorated with self-assembled peptide nanowires as sensitive materials for the first time. When employing a conventional drop-casting method for decorating self-assembled peptide nanostructures onto a QCM electrode surface, observed sensor signals significantly exhibited background noise via unintentional energy dissipations. To overcome this inherent problem of depositing peptide self-assemblies, we developed an on-site growth method of peptide nanowires directly grown from a peptide amorphous film on a QCM electrode surface. The QCM sensors fabricated by the on-site growth method exhibited smaller background noise with lower energy dissipation, resulting in successful amine selective sensing. Thus, the present method using on-site growth will be a foundation to apply various functional peptide nanostructures to QCM gas sensors.

Evolution and Reconstruction of Air-Electrode Surface Composition in Reversible Protonic Ceramic Cells: Mechanisms, Impacts on Catalytic Performance, and Optimization Strategies - A Review.

Reversible protonic ceramic cells (R-PCCs) are at the forefront of electrochemical conversion devices, capable of reversibly and efficiently converting chemical energy into electricity at intermediate temperatures (350-700°C) with zero carbon emissions. However, slow surface catalytic reactions at the air-electrode often hinder their performance and durability. The electrode surface is not merely an extension of the bulk structure, equilibrium reconstruction can lead to significantly different crystal-plane terminations and morphologies, which are influenced by material's intrinsic properties and external reaction conditions. Understanding electrode surface evolution at elevated temperatures in water-containing, oxidative atmospheres presents significant importance. In this review, a comprehensive summary of recent processes in applying advanced characterization techniques for high-temperature electrode surfaces is provided, exploring the correlations between surface evolution and performance fluctuations by examining the structural evolution and reconstruction of various air-electrode surfaces associated with degradation and activation phenomena, offering insights into their impact on electrode performance. Furthermore, reported strategies and recent advances in enhancing the electrochemical performance of R-PCCs through engineering air-electrode surfaces is discussed. This review offers valuable insights into surface evolution in R-PCCs and is expected to guide future developments in high-temperature catalysis, solid-state ionics, and energy materials.

Multivalent Redox Reversible Conversion-Enhanced Electrochemiluminescence Strategy for Progesterone Detection.

The performance of electrochemiluminescence (ECL) sensing platforms, especially the sensitivity, relies on an efficient signal enhancement mechanism and presents a critical challenge in developing novel strategies simultaneously. In this work, we reported a multivalent redox reversible conversion-enhanced ECL strategy based on the redox reactions of two pairs of multivalent metal elements on the electrode surface. TiO2-loaded Eu(OH)3 (Eu(OH)3@TiO2) was introduced as a dual-enhanced coreactant accelerator to catalyze the oxidation process of tripropylamine (TPrA), thus improving the reaction rate at the sensing interface and the ECL strength of the luminophore. Moreover, gadolinium hydroxide (Gd(OH)3) served as the ECL emitter for the sensing platform. The stable luminescence property of Gd(OH)3 was observed, laying the foundation for its application in ECL sensing. To construct the immunosensor, a heptapeptide affinity ligand (HWRGWVC, HGC) was introduced to oriented immobilize antibodies. HGC effectively maintained the biological activity, thus improving the incubation efficiency and detection performance of the immunosensor. In this study, a competitive ECL immunoassay model was designed for the sensitive detection of progesterone (P4). The competitive immunosensor exhibited a broad range of 0.001-200 ng·mL-1 and a low detection limit of 0.38 pg·mL-1. The competitive sensing model based on the dual-enhanced strategy is expected to offer a prospective approach to precise detection.

The Interpretation of Carbon Nanotubes’ Electrochemistry: Electrocatalysis and Mass Transport Regime in the Apparent Promotion of Electron Transfer

Carbon nanotubes (CNTs) are widely used in electrochemical sensors due to their significant impact on the electroanalytical signal. However, there remain significant doubts regarding the origin of the improved electroanalytical response observed in CNT-based sensors, particularly concerning the precise role of CNTs in these systems. In particular, the origin of the electrochemical response is controversial, as it may be due to either electrocatalytic or non-electrocatalytic processes. The latter implies that the electroanalytical response is mainly governed by the mass transport phenomena within the porous CNT layer. This article briefly reviews the several comprehensive models based on the role of porosity (diffusion in a ‘thin-layer’) on the electrochemical behavior as well as on the electrocatalytic properties of CNTs to resolve conflicts arising from misinterpretations of the electroanalytical response of CNT-based sensors. However, even though there are some explanations and conclusions on this topic, they seem to be valuable for specific electroactive species, the type of CNTs and/or electrode architecture, the electrode surface, etc. Accordingly, general theories and conclusions are not yet defined, so different approaches to this topic are still needed, since the main phenomenological effects responsible for the nature of the electrochemical response of the electrodes modified with CNTs need to be determined in a rational way.

Synergy in Commercial Brass Reinforced Carbon Hybrids Interlayer towards Highly Reversible Zn Anodes

Aqueous Zn‐ion batteries (AZIBs) have served as a promising candidate for next‐generation energy storage applications. Nonetheless, interfacial issues concerning the metallic Zn anode including hydrogen evolution reaction (HER), chemical corrosion, and dendrite growth remain to be carefully addressed. Herein, we present a facile and cost‐effective strategy to implant carbon nanotube (CNT) framework with a commercial brass alloy as the protective interlayer. The conductive network constructed by interconnected CNTs ensures an optimal electric field distribution over the entire electrode surface. The embedded brass alloy not only inhibits the aggregation of CNTs, but also mitigates surface corrosion through its abundance of chemically inert Cu sites. Leveraging the synergy within the carbon hybrids featuring high Zn‐affinity and abundant nucleation sites for Zn2+, lowered energy barriers and promoted redox kinetics for Zn deposition enable highly stabilized and reversible Zn anodes. As a result, symmetric cells demonstrate extended cycling lifespan of 3000 h and 1200 h at 2 mA cm−2 and 5 mA cm−2 for 1 mAh cm−2, respectively. Furthermore, the optimized Zn||MnO2 full cells exhibit impressive cycling stability for 1000 cycles at 2 A g−1.

Reinventing the High-rate Energy Storage of Hard Carbon: the Order-degree Governs the Trade-off of Desolvation -Solid Electrolyte Interphase at Interfaces.

In alkali metal-ion battery systems, the electrolyte enables being decomposed on the electrode surface to form a solid electrolyte interphase film (SEI). In principle, a thin, uniform SEI film facilitates to enhancement of the performance of the cell. Herein, we successfully distinguish the effects of desolvation behavior and SEI process on the kinetic behavior of hard carbon (HC) electrodes by adopting the strategy of switching the electrolyte interface model to modulate the properties of SEI film. Our findings reveal that although the SEI film is generally responsible for significantly affecting the HC's capacity, the equally crucial desolvation process must not be overlooked. The trade-off between the two factors is found to be determined by the structural features of HCs. Specifically, in the context of a more ordered HC, the desolvation of ions emerges as the rate-limiting step for Na+ transport across the electrode/electrolyte interface, exerting a more pronounced effect rather than the SEI. Thus, a close correlation was established between the SEI, solvation structure effects, hard carbon structure, and electrode performance. This linkage is thereof fundamental for the strategic design of electrolytes and the targeted enhancement of cell performance.

Accelerating Ion Desolvation via Bioinspired Ion Channel Design in Nonconcentrated Aqueous Electrolytes.

In aqueous-based electrochemical energy storage devices, uncontrolled hydrolysis of water at the electrochemical interfaces limits the application of such aqueous batteries or supercapacitors in business. The "water-in-salt" design is a valid strategy to broaden the electrochemical stability window in aqueous electrolytes, but drawbacks such as high manufacturing cost, high electrolyte viscosity, etc., also hinder its development. Here, inspired by biological ion channels in cell membranes, we propose an effective approach to engineer the electrode surface, inducing the desolvation of hydrated ions at the electrochemical interface and inhibiting water decomposition in nonconcentrated electrolytes. The biological engineering strategy enables the induction of controlled desolvation and accelerates the transportation of hydrated ions, e.g., potassium. The subnanometer design (0.8 nm) forces the hydrated potassium ions to shed their solvation shell with a hydration number of only 0.3, while the electrostatic interactions between the pore groups and the potassium ions facilitate their transport. The Zn||Zn cells demonstrate a stable cycling lifespan of over 1000 h at 1 mA cm-2/10 mAh cm-2. This work sheds new light on regulating the electrochemical interfaces in low-concentration aqueous electrolytes for designing aqueous-based energy storage devices.

Reinventing the High‐rate Energy Storage of Hard Carbon: the Order‐degree Governs the Trade‐off of Desolvation —Solid Electrolyte Interphase at Interfaces

In alkali metal‐ion battery systems, the electrolyte enables being decomposed on the electrode surface to form a solid electrolyte interphase film (SEI). In principle, a thin, uniform SEI film facilitates to enhancement of the performance of the cell. Herein, we successfully distinguish the effects of desolvation behavior and SEI process on the kinetic behavior of hard carbon (HC) electrodes by adopting the strategy of switching the electrolyte interface model to modulate the properties of SEI film. Our findings reveal that although the SEI film is generally responsible for significantly affecting the HC’s capacity, the equally crucial desolvation process must not be overlooked. The trade‐off between the two factors is found to be determined by the structural features of HCs. Specifically, in the context of a more ordered HC, the desolvation of ions emerges as the rate‐limiting step for Na+ transport across the electrode/electrolyte interface, exerting a more pronounced effect rather than the SEI. Thus, a close correlation was established between the SEI, solvation structure effects, hard carbon structure, and electrode performance. This linkage is thereof fundamental for the strategic design of electrolytes and the targeted enhancement of cell performance.

Extensive adjustment of magnetic field on plasma density and ion incidence angle in radio frequency discharge

Abstract The impact of an inhomogeneous magnetic field generated by supplementary direct current coils on the uniformity of capacitively coupled discharges is examined utilizing a two-dimensional implicit particle-in cell/Monte Carlo model. Typically, at low-pressure, the radial density distribution of plasma is characterized by a high density at the center of the chamber and a lower density near the periphery. This results in nonuniform radial plasma density profiles and large ion impact angles at the electrode. We find that placing a direct current coil above the chamber produces a non-uniform static magnetic field, which facilitates the transport of plasma species toward the electrode periphery, resulting in a more uniform plasma density distribution. Nonetheless, this approach leads to a decrease in central density and adversely affects the ion incident angles near the chamber's center. Consequently, this compromise undermines both the efficiency and uniformity of processes occurring in the central region of the chamber. To overcome these limitations, we propose innovative coil configurations, specifically dual direct current coils comprising an inner and an outer coil. The outer coil, situated above the chamber, has a larger radius, while the inner coil, positioned either above or below the chamber, has a smaller radius. Additionally, the currents in the inner and outer coils flow in opposite directions. Our findings indicate that the outer coil predominantly governs the density distribution across the entire electrode surface, while the inner coil allows for precise adjustment of the plasma density near the discharge center. Therefore, by adjusting the currents of the outer and inner coils, significant improvements can be achieved in both the uniformity of plasma density and the vertical alignment of the ion angles above the electrode. These factors are critical for the fabrication of high aspect ratio microelectronic structures.

Self‐Supported Ni/Ni(OH)2 Electrodes for High‐Performance Alkaline and AEM Water Electrolysis

AbstractA novel tape‐cast Ni/Ni(OH)2 electrode is developed for water electrolysis applications. Through precise control of sintering temperature and in situ formation of Ni(OH)2 nanosheets, the electrode achieves an optimized hierarchical porous structure with interconnected channels, facilitating efficient gas bubble transport and release. The electrode exhibits remarkable hydrogen evolution reaction activity with overpotentials of 40 and 124 mV at 10 and 100 mA cm−2, respectively, comparable to noble metal catalysts. The unique microstructure enables rapid bubble detachment and enhanced mass transport, leading to a high current density of 0.91 A cm−2 at 1.8 V in alkaline water electrolysis. The inherent Ni/Ni(OH)2 composition demonstrates excellent stability over 1500 h of continuous operation and maintains consistent performance under intermittent conditions, making it particularly suitable for renewable energy integration. For anion exchange membrane water electrolysis, the electrode's smooth surface morphology prevents membrane damage while maintaining efficient mass transport, delivering 0.4 A cm−2 at 1.8 V. This study demonstrates that rational design of electrode microstructure through tape‐casting offers a promising pathway toward high‐performance, durable, and cost‐effective water electrolyzers.

Oxygen Evolution Enhancement of Nickel (Hydr)Oxide via Iron Coordination Compound in Alkaline Conditions.

This study investigates the complex dynamics of the oxygen-evolution reaction (OER) in systems involving Ni(Fe) (hydr)oxides and the iron coordination compound Fe phthalocyanine-4,4',4″,4‴-tetrasulfonate. It offers a novel perspective on the interaction between nickel hydroxide and the Fe compound during the OER process. The Fe complex facilitates the controlled release of trace Fe ions into the Ni (hydr)oxides as it undergoes degradation or demetalation within the Ni(II)/(III) potential range. Once the electrode surface reaches saturation with Fe, additional contributions from Fe have minimal impact on OER activity, and the turnover frequency rapidly reaches its maximum value (approximately 1 s-1) under cyclic voltammetry. In situ Raman spectroscopy reveals that the interaction between the iron complex and the electrode surface, as well as the amount of complex deposited or adsorbed, depends on the applied potential of the electrode. Changes in the electrode's potential influence how the Fe complex binds to the surface, through mechanisms such as electrostatic attraction, chemical bonding, or other interactions. This underscores the critical role of potential control in optimizing electrode surface modifications and enhancing the efficiency of electrochemical processes involving the iron complex.

Investigating the Impact of EDM Parameters on Surface Roughness and Electrode Wear Rate in 7024 Aluminum Alloy

Electrical Discharge Machining (EDM) is a significant process in the industry for machining hard metals. It is a time-consuming and costly method that requires a high level of expertise to operate effectively. EDM is considered one of the unconventional operating processes due to its unique characteristics and the challenges associated with its implementation. One of the challenges facing researchers is determining the optimal parameters for achieving high surface quality while minimizing equipment consumption and associated costs. In addition to being classified as one of the operating processes, EDM processes are also classified as electro-thermal processes that affect surface quality. In this study, the influence of EDM parameters on surface roughness and electrode wear rate when machining aluminum alloy type 7024 was investigated. A total of 27 experiments were conducted to evaluate the impact of three parameters at three levels. The parameters under investigation include current, pulse on time, and pulse off time. Subsequent analysis of the results by variance analysis revealed that the most influential parameter for both surface roughness and electrode wear rate is electric current, with a rate of influence of 74%. The results were then subjected to further analysis using variable effect graphs to identify the optimal variables for achieving the best results. Finally, neural networks were employed to predict the results, with an accuracy of up to 99%.

Determination of Best Input Factors in Powder-Mixed Electrical Discharge Machining 90CrSi Steel using Multi-Criteria Decision Making Methods

This article outlines the results of a Multi-Criteria Decision Making (MCDM) analysis conducted on the Powder-Mixed Electrical Discharge Machining (PMEDM) process for cylindrical parts fabricated from 90CrSi tool steel, using graphite electrodes. The study aims to identify the optimal input factors to simultaneously minimize Surface Roughness (SR) and Electrode Wear Rate (EWR), while maximizing Material Removal Speed (MRS). Five input factors were selected: powder concentration (CP), pulse-on time (Ton), pulse-off time (Toff), pulse current (IP), and servo voltage (SV). Experimental data were generated using the Taguchi method with an L18 design. The optimization process was performed using the Multi-Attributive Border Approximation area Comparison (MABAC), Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), and Evaluation by an Area-based Method of Ranking (EAMR) methods. Criteria weights were calculated utilizing the Entropy and the Multi-Expert Ranking Evaluation with Compensation (MEREC) techniques. The analysis identified the best PMEDM input factor, providing an optimal solution for enhancing the efficiency of machining cylindrically shaped components.

Specific Nickel recovery using screen-printed carbon electrode electrografted with ionic liquid

This study presents an innovative electrochemical method for selectively extracting nickel ions from aquatic solutions, employing electrodes enhanced with electrografted ionic liquids. Specifically, a styrenyl-imidazolium ionic liquid (SI-IL) was synthesized, featuring a double bond for immobilization and an imidazole group targeting nickel ions. The electrografting process ensured uniform SI-IL distribution on the electrode's surface, as confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). SI-IL-treated electrodes exhibited notable selectivity towards nickel ions, efficiently recovering them as nanoparticles while reducing the required reduction potential. In pH conditions similar to industrial wastewater, SI-IL modified electrodes demonstrated substantial enhancement in nickel recovery rates compared to unmodified electrodes.

The influence of electrode crack dimensions on the durability of polymer electrolyte membrane fuel cells

Electrode cracks in polymer electrolyte membrane fuel cells (PEMFCs) are correlated with early onset failures. In this work we investigate the influence of cracked gas diffusion electrodes (GDEs) on the durability of the membrane electrode assembly (MEA) using a combined chemical-mechanical accelerated stress test (AST). Electrode crack dimensions were systematically tuned using ink formulations and material selection strategies. A parameter to describe the crack width areal density (ΦCW) was used to quantify the degree of discontinuity in the electrode surfaces. Open circuit voltage (OCV) transient analyses were used to benchmark and characterize the failure mechanisms in the MEAs as a function of the ΦCW. While smaller electrode-level cracks, on the order of microns, yielded a 28 % decrease in operating lifetime, larger cracks that propagated from a discontinuous, microporous layer (MPL) coating, decreased the operating lifetime by 56 %. This work emphasizes the need for material processing strategies that consider defect tolerances to limit membrane failures in PEMFCs.

Electrolyte reactivity on electrode surfaces for active species formation and Reactive Red X-3B degradation in electrochemical treatment of dyeing wastewater.

The pivotal role of electrolytes such as Na2SO4 and NaCl in electrochemical treatment of dyeing wastewater was investigated by comparing recalcitrant Reactive Red X-3B (RRX-3B) degradation rates, active species formation and intermediates generation in a double-chamber cell. It was found that similar reactive oxygen species (ROS) formed in the anodic chamber are •OH and 1O2, in the cathodic chamber is •O2- with different electrolytes, while this is not the case for ROS contribution, RRX-3B degradation kinetic and intermediates. NaCl favored the generation of 1O2, faster decolorization (-N=N- cleavage), and organic intermediates degradation in the anodic chamber. A comparatively faster hydrogenation reduction of -N=N- and higher COD removal with fewer organic categories in Na2SO4 cathodic chamber outperformed those in NaCl cathodic chamber. The RRX-3B degradation pathways were proposed in both chambers based on GC-MS investigations and Fukui function calculations. Atoms Cl, S and N in RRX-3B molecule removals were in the order of R-S>R-N>R-Cl.

Ethyl 2-butene phosphite as a film-forming additive for high voltage lithium-ion batteries

Increasing the charge cutoff voltage can significantly improve the capacity of lithium-ion batteries. However, the structural degradation of Ni-rich cathodes and high reactivity of electrolytes at the high-potential cathodes greatly affect the cycling stability. In this paper, a new type of cathode film-forming additive, ethyl 2-butene phosphite (EBP), is synthesized based on the molecular design of phosphite by increasing the functional group of carbon-carbon double bond and ring structure. Theoretical calculation shows that EBP has a higher HOMO level and can form a cathode electrolyte interphase (CEI) on the cathode electrode surface before the electrolyte in theory. The electrochemical performance of NCM622/Li half-cells is significantly enhanced by incorporating EBP into the electrolyte, achieving 72.52% capacity retention over 100 cycles at 0.5C. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive Spectroscopy (EDS) are used to characterize the morphology of the anode and cathode, revealing that EBP forms a dense and complete CEI film on the surface of the LiNi0.6Co0.2Mn0.2O2 electrode. This film effectively blocks direct contact between the electrolyte and the cathode active material, prevents the dissolution of transition metals, improves interfacial stability, and consequently enhances the high-voltage cycling performance of the battery.

Cocatalysis of catalytic hairpin assembly and ternary heterojunction Bi2S3@MoS2@Bi2MoO6 promotes ultra-sensitive electrochemical of detection MiRNA-21.

Ternary heterojunction Bi2S3/MoS2/Bi2MoO6 was designed as a signal probe to develop a dual signal amplification strategy empowered electrochemical biosensor for sensitive miRNA-21 detection by combining with catalytic hairpin assembly (CHA). The combination of the Bi2S3/MoS2/Bi2MoO6 heterojunction as a tracer indication probe and the CHA amplification strategy not only took fully use of the highly dense nanowire interwoven structure and superior active region of the probe, but also endowed the ability to improve the molecular hybridization efficiency by collision, which significantly avoided the cumbersome chain design and greatly simplified the step-by-step construction of the electrode surface. Hairpin H1 was first added dropwise to the gold nanoparticle-decorated electrode surface, and then opened by the introduced miRNA-21 to initiate the specific hybridization. Once the H2-MB/Bi2S3/MoS2/Bi2MoO6 heterojunction was added, more sensitive and rapid detection of miRNA-21 would be achieved through the introduction of methylene blue since the cocatalysis of hairpin assembly and ternary heterojunction Bi2S3@MoS2@Bi2MoO6. Finally, the constructed biosensor demonstrated effective performance in the detection of miRNA-21 within the linear range of 1 fM to 100pM with a detection limit of 0.31 fM. The satisfactory analysis of human blood samples further validated the preferable reliability and practicability of this new strategy for the ultrasensitive detection of miRNA.

Intensification of Alkaline Electrolyzer with Improved Two‑Phase Flow

AbstractGreen hydrogen produced through water electrolysis offers a promising pathway to global decarbonization. Among various electrolyzers, alkaline water electrolysis (AWE) is the most established and commercially mature. To reduce the cost of hydrogen production from AWE, it is crucial to increase operational current density while maintaining or lowering voltage to increase hydrogen yield and reduce energy consumption. Such efforts are focused on reducing the ohmic resistance at high current densities through the implementation of alkaline membranes. However, this work underlines that the ohmic resistance at high current densities is also influenced by the losses associated with the evolution of bubbles at the electrode surface and two‐phase mass transfer. This is shown by investigating the impact of tortuosity and bubble point of porous electrodes on AWE performance. Low‐tortuosity porous nickel electrodes are fabricated and analyzed for their ability to reduce capillary pressure and bubble point, resulting in lower energy losses and improved efficiency. The cell reaches an industrially appealing relevant current density of 2 A cm−2 at ≈2 V. Besides test in single cells, the advantageous effect of these low tortuosity porous nickel electrodes are also validated in a kW‐class AWE stack, confirming their effectiveness in enhancing overall system performance.

New Amperometric Glucose Biosensors Based On Nafion Nanofibers

In this study, we present new amperometric glucose biosensorsbased on Nafion nanofibers. Nafion possesses a number of desirable properties, including stability, thermal, mechanical, physio-chemical and biocompatibility, which make it a competitive polymer for use in glucose biosensors. Nafion nanofibers were produced using a low-cost electrospinning method, and their morphology was characterized via scanning electron microscopy (SEM). The biosensors were fabricated by loading glucose oxidase (GOx) and GOx-AuNPs (10 nm) on the Nafion-Cellulose Acetate nanofibers(Nafion-CA Nfs) (461.53 ± 30.34 nm) on the surface of a platinum electrode, followed by cross-linking using glutaraldehyde. The biosensors operating at 0.6 V demonstrated lower LODs with wider linear ranges, enhanced stability, elevated sensitivity, and improved selectivity. For Pt/Nafion-CA NFs/GOx biosensor demonstrated remarkable sensitivity, with values of 68.67 μA.mM-1cm-² and 18.38 μA.mM-1.cm-², respectively, and a limit of detection (LOD) of 1.36 μM. Meanwhile, the Pt/Nafion-CA NFs/ GOx-AuNPsbiosensor achieved sensitivities of 55.56 μA.mM-1.cm² and 28.49 μA/mM·cm², respectively. It also exhibited a broad linear range of up to 12.81 mM and an LOD of 10.8 μM, with no observable interference effects. The present studies highlight the potential of Nafion nanofibersas a suitable matrix for immobilizingGOx and GOx-AuNPs, thereby demonstrating their viability as interference-free, easy-to-use sensors with good sensitivity, LOD and stability for commercialization.