Electrochemical Systems Research Articles

Synthesis and characterization of Cu-modified ox-g-C3N4 nanosheets as an electrode for green synthesis of phenyl Benzofuran derivatives via C–H functionalization to C–O and C–C bond formation with an electrochemical oxidation system

Synthesis and characterization of Cu-modified ox-g-C3N4 nanosheets as an electrode for green synthesis of phenyl Benzofuran derivatives via C–H functionalization to C–O and C–C bond formation with an electrochemical oxidation system

Carbon foam to enhance the performance of a slurry flow energy system used for hydrogen storage and transportation: An experimental investigation

A novel idea of using carbon foam (CF) is introduced to enhance the electrochemical performance of a slurry electrode system in a proton flow reactor system. Steam-activated and acid-washed Norit from peat is used as active charge carrier particles to prepare 15 wt% carbon slurry to be used in this study. The slurry flow rates in the experimental electrochemical system can be varied from 0 to 200 ml min−1, while using two channel widths of 1.6 cm and 2 cm to facilitate the slurry flow. Two sets of CFs with 10 pores per inch (PPI) and 5 PPI are used to understand the effect of introducing CFs with different pore sizes on the performance of slurry electrode. Slurry is charged slurry up to 100 C under constant application of 10 mA and 30 mA. After adding CF, the results show a significant drop in charging potential to generate both levels of current of 25% after using 5 PPI and 41% with 10 PPI. Furthermore, using the narrow channel flow of 1.6 cm and increasing the slurry flow rate from 100 ml min−1 to 150 ml min−1 lower the charging potential considerably by 19% and 21% (compared to base slurry) for 5 PPI and 10 PPI CF, respectively. Application of CF further enables the system to attain higher discharging time during the discharge cycle, and a maximum of 336% and 115% discharging capacity improvement is observed with 10 PPI and 5 PPI CF, respectively.

Upgrading Electrolyte Antioxidant Chemistry by Constructing Potential Scaling Relationship.

Rational design of advanced electrolytes to improve the high-voltage capability has been attracting wide attention as one critical solution to enable next-generation high-energy-density batteries. However, the limited understanding of electrolyte antioxidant chemistry as well as the lack of valid quantization approaches have resulted in knowledge gap, which hinders the formulation of new electrolytes. Herein, we construct a standard curve based on representative solvation structures to quantify the oxidation stability of ether-based electrolytes, which reveals the linear correlation between the oxidation potential and the atomic charge of the least oxidation-resistant solvent. Dictating by the regularity between solvation composition and oxidation potential, a (Trifluoromethyl)cyclohexane-based localized high-concentration electrolyte dominated by anion-less solvation structures was designed to optimize the cycling performance of 4.5 V 30-μm-Li||3.8-mAh cm-2-LiCoO2 batteries, which maintained 80% capacity retention even after 440 cycles. The consistency of experimental and computational results validates the proposed principles, offering a fundamental guideline to evaluate and design aggressive electrochemical systems.

High-Entropy Configuration Strategy to Build High Performance Na-Ion Layered Oxide Cathodes Derived from Simple Techniques.

Layered transition metal oxides are commonly used as the cathode materials in sodium-ion batteries due to their low cost and easy manufacturing. However, the application is hindered by poor rate performance and complex phase transitions. To address these challenges, a new seven-component high-entropy layered oxide cathode material, O3-NaNi0.25Fe0.15Mn0.3Ti0.1Sn0.05Co0.05Li0.1O2 (HEO) has been developed. The entropy stabilization effect plays a crucial role in improving the performance of electrochemical systems and the stability of structures. The HEO exhibits a specific discharge capacity of 154.1 mA h g-1 at 0.1 C and 94.5 mA h g-1 at 7 C. In-situ and ex-situ XRD results demonstrate that the HEO effectively retards complex phase transitions. This work provides a high-entropy design for the storage materials with a high energy density. Meanwhile, it eliminates industry doubts about the performance of sodium ion layered oxide cathode materials.

A Hybrid-Salt Strategy for Modulating the Li+ Solvation Sheathes and Constructing Robust SEI in Non-Flammable Electrolyte Lithium Metal Batteries.

The electrode interface determines the performance of an electrochemical energy storage system. Using traditional electrolyte organic additives and high-concentration electrolyte emerging recently are two generally strategies for improving the electrode interface. Here, a hybrid-salt electrolyte strategy is proposed for constructing the stable electrode interface. Through the solubilization effect of phosphate ester on LiNO3, a hybrid-salts-based non-flammable phosphate ester electrolyte system (HSPE) with LiPF6 and LiNO3 as Li salts has been developed. By the strong interaction between NO3 - and Li+, the Li+ solvation sheath and solvent behaviors have been modulated, thus the undesirable effects of phosphate ester are eliminated and a robust SEI is formed. Experimental results and theoretical calculations illustrate that NO3 - as a kind of strongly coordinating anion can reduce the number of TEP molecules and lower the reduction reactivity of TEP. The reconfigured Li+ solvation structure allows the formation of an inorganic-rich SEI on the electrode surface. As a result, in the designed HSPE, the average coulombic efficiency of lithium plating/stripping is increased to 99.12 %. This work explored a new approach to construct the electrode interface and addressing the poor interface performance issue of phosphate esters.

Enhancement of Li/S Battery Performance by a Modified Reduced Graphene Oxide Carbon Host Decorated with MoO3.

Electrochemical energy storage systems based on sulfur and lithium can theoretically delivery high energy with the further benefit of low cost. However, the working mechanism of this device involves the dissolutions of sulfur to high-molecular weight lithium polysulfide (LiPs with general formula Li2Sn, n>4) in the electrolyte during the discharge process. Therefore, the resulting migration of partially dissociated LiPs, by diffusion or under the effect of the electric field, to the lithium anode activates an internal shuttle mechanism, reduces the active material and in general leads to loss of performance and a reduced cycling stability. These drawbacks poses challenges to the commercialization of Li/S cells in the short term. In this study, we report on the decoration of reduced graphene oxide with MoO3 particles to enhance interactions with LiPs and retain sulfur at the cathode side. The combination of experiments and density functional theory calculation demonstrated improvements in binding interactions between the cathode and sulfur species, enhancing the cycling stability of the Li/S half-cell.

A Physics-based Model Assisted by Machine-Learning for Sodium-ion Batteries with both Liquid and Solid Electrolytes

Abstract In the absence of experimental data of a fully developed hierarchical 3D sodium solid state batteries, we developed an improved continuum model by relying on Machine Learning-assisted parameter fitting to uncover the intrinsic material properties that can be transferred into different battery models. The electrochemical system simulated has sodium metal P2-type Na2/3[Ni1/3Fe1/12Mn7/12]O2 (NNFMO) as the cathode, paired with two types of electrolytes have been modeled viz, the organic liquid electrolyte and a solid polymer electrolyte. We implemented a 1D continuum model in COMSOL to suit both liquid and solid electrolytes, then used a Gaussian Process Regressor to fit and evaluate the electrochemical parameters in both battery systems. To enhance the generalizability of our model, the liquid cell and solid cell models share the same OCV input for the cathode materials. The resulting parameters are well aligned with their physical meaning and literature values. The continuum model is then used to understand the effect of increasing the thickness of the cathode and current density by analysing the cathode utilization, and the overpotentials arising from transport and charge transfer. This 1D model and the parameter set are ready to be used in a 3D battery architecture design.

The Role of Alkali Cations on the Selectivity of 5-Hydroxymethylfurfural Electroreduction on Glassy Carbon.

In the past decade, organic electrosynthesis has emerged as an atom- and energy-efficient strategy for harvesting renewable electricity that provides exceptional control over the reaction parameters. A profound and fundamental understanding of electrochemical interfaces becomes imperative to advance the knowledge-based development of electrochemical processes. The major strategy toward an efficient electrochemical system is based on the advancement in material science for electrocatalysis. Studies on the complex interplay among electrode surface, electrolyte, and transformation intermediates have only recently started to emerge. It involves acquiring atomic-scale insights into the electrochemical double layer, for which the identity and concentration of composing ions play a crucial role. In this study, we present how the identity and concentration of alkali cations impact the selectivity of aldehyde functionality electroreduction. As a case-study transformation, we set the electrochemical conversion of 5-hydroxymethylfurfural (HMF), a promising biomass-derived feedstock for the sustainable production of polymer or fuel precursors. Our findings reveal a consistent trend of the selectivity shift towards 2,5-bis(hydroxymethyl)furan (BHMF) as a function of cation size and concentration, rationalized by specific cation adsorption at the glassy carbon (GC), followed by the increase in the electrode surface charge density.

Specific Small-Molecule Detection Using Designed Nucleic Acid Nanostructure Carriers and Nanopores.

In the realm of nanopore sensor technology, an enduring challenge lies in achieving the discerning detection of small biomolecules with a sufficiently high signal-to-noise ratio. This study introduces a method for reliably quantifying the concentration of target small molecules, utilizing tetrahedral DNA nanostructures as surrogates for the captured molecules through a magnetic-bead-based competition substitution mechanism. Magnetic Fe3O4-DNA tetrahedron nanoparticles (MNPs) are incorporated into a nanopore electrochemical system for small-molecule sensing. In the presence of the target, the DNA tetrahedron, featuring an aptamer tail acting as a molecular carrier, detaches from the MNPs due to aptamer deformation. Following removal of the MNPs, the DNA tetrahedron bound to the target traversed the nanopore by applying a positive potential. This approach exhibits various advantages, including heightened sensitivity, selectivity, an improved signal-to-noise ratio (SNR), and robust anti-interference capabilities. Our findings demonstrate that this innovative methodology has the potential to significantly enhance the sensing of various small-molecule targets by nanopores, thereby advancing the sensitivity and dynamic range. This progress holds promise for the development of precise clinical diagnostic tools.

Optimal charging for lithium-ion batteries to avoid lithium plating based on ultrasound-assisted diagnosis and model predictive control

Lithium plating in lithium-ion batteries for electric vehicles, occurring due to low-temperature or high-rate charging, is a significant factor impacting safety and service life. To address this issue, a novel adaptive charging approach is proposed, combining ultrasound-assisted diagnosis and model predictive control (MPC). In the method, a discrete state-space electrochemical model is used to describe the dynamic characteristics of the battery, and a model predictive controller (MPC) is utilized to optimize the charging current to avoid lithium plating. Considering that factors such as battery performance degradation and variable working temperature affect the battery model's judgment of lithium plating, an ultrasound-assisted diagnosis method is used to determine the critical point of lithium plating. The effectiveness of the method is validated through low-temperature charging and cycle aging experiments. The results indicate that without complex model parameter calibration in different temperatures, the new charging method not only has a higher charging speed than constant current charging, but also can effectively suppress the occurrence of lithium plating on the negative electrode of the battery. The method is expected to be applied in electrochemical energy storage systems to enhance safety and service life.

Sub-nanopores enabling optimized ion storage performance of carbon cathodes for Zn-ion hybrid supercapacitors

Aqueous Zn-ion hybrid supercapacitors (ZHSs) are attracting significant attention as a promising electrochemical energy storage system. However, carbon cathodes of ZHSs exhibit unsatisfactory ion storage performance due to the large size of hydrated Zn-ions (e.g., [Zn(H2O)6]2+), which encumbers compact ion arrangement and rapid ion transport at the carbon-electrolyte interfaces. Herein, a porous carbon material (HMFC) with abundant sub-nanopores is synthesized to optimize the ion storage performance of the carbon cathode in ZHSs, in which the sub-nanopores effectively promote the dehydration of hydrated Zn-ions and thus optimize the ion storage performance of the carbon cathode in ZHSs. A novel strategy is proposed to study the dehydration behaviors of hydrated Zn-ions in carbon cathodes, including quantitatively determining the desolvation activation energy of hydrated Zn-ions and in-situ monitoring active water content at the carbon-electrolyte interface. The sub-nanopores-induced desolvation effect is verified, and its coupling with large specific surface area and hierarchically porous structure endows the HMFC cathode with improved electrochemical performance, including a 53 % capacity increase compared to the carbon cathode counterpart without sub-nanopores, fast charge/discharge ability that can output 46.0 Wh/kg energy within only 4.4 s, and 98.2 % capacity retention over 20,000 charge/discharge cycles. This work provides new insights into the rational design of porous carbon cathode materials toward high-performance ZHSs.

A sustainable electrochemical strategy utilizing pulsed alternating current and dual carbon felt electrodes for enhanced degradation of organic pollutants: Oxidation performance and mechanisms

In this work, a novel electrochemical (EC) oxidation system utilizing pulsed alternating current (PAC) and dual carbon felt (CF) electrodes has been established for sustainable degradation of sulfamethoxazole (SMX) with no addition of extra oxidant. The EC/PAC system showed high degradation efficiency and energy efficiency compared to the pulsed direct current (PDC) and direct current (DC) systems. The EC/PAC process was effective across a wide pH range of 3–11 for SMX removal. The results showed that the 1O2 confined to the CF electrode surface was the dominant oxidative specie that was generated from dissolved oxygen in the system. Under PAC conditions, the cathode and anode were rapidly switched on the same CF electrode, increasing the generation of 1O2 for enhanced SMX oxidation. Furthermore, the EC/PAC system demonstrated resistance to interference from various anions of different concentration levels found in natural environment. In contrast to the EC/PDC system, the EC/PAC system emerged as a promising option for more efficient H2O2 production. High-resolution mass spectrometry results revealed the SMX degradation pathways and byproducts, which were then evaluated for toxicity removal. Overall, the EC/PAC system offers a green and sustainable solution to future wastewater treatment, with high degradation rates, energy efficiency, and sustainability.

Immobilization-free and label-free electrochemical DNA biosensing based on target-stimulated release of redox reporter and its catalytic redox recycling

Herein, we demonstrate a simple, homogenous and label-free electrochemical biosensing system for sensitive nucleic acid detection based on target-responsive porous materials and nuclease-triggered target recycling amplification. The Fe(CN)63− reporter was firstly sealed into the pores of Fe3O4 nanoparticles by probe DNA. Target DNA recognition triggered the controllable release of Fe(CN)63− for the redox reaction with the electron mediator of methylene blue enriched in the dodecanethiol assembled electrode and thereby generating electrochemical signal. The exonuclease III (Exo III)-assisted target recycling and the catalytic redox recycling between Fe(CN)63− and methylene blue contributed for the enhanced signal response toward target recognition. The low detection limit toward target was obtained as 478 fM and 1.6 pM, respectively, by square wave voltammetry and cyclic voltammetry methods. It also possessed a well-discrimination ability toward mismatched strands and high tolerance to complex sample matrix. The coupling of bio-gated porous nanoparticles, nuclease-assisted target amplification and catalytic redox recycling afforded the sensing system with well-controllable signal responses, sensitive and selective DNA detection, and good stability, reusability and reproducibility. It thus opens a new avenue toward the development of simple but sensitive electrochemical biosensing platform.

Non-destructive and simultaneous development and enhancement of latent fingerprints on stainless steel based on the electrochromic effect of electrodeposited manganese oxides

Latent fingerprints, as one of the most frequently encountered traces in crime scene investigation and also one of the largest sources of forensic evidence, can play a critical role in determining the identity of a person who may be involved in a crime. Due to the invisible characteristic of latent fingerprints, exploring efficient techniques to visualize them (especially the ones resided on metallic surfaces) while retain the biological and chemical information (e.g., touch DNA) has become a multidisciplinary research focus. Herein we reported a new and highly sensitive electrochemical interfacial strategy of simultaneously developing and enhancing latent fingerprints on stainless steel based on synchronous electrodeposition and electrochromism of manganese oxides in a neutral aqueous electrolyte. By utilizing a specially designed device for electrochemical testing and image capture, a series of electrochemical measurements, physical characterization and image analysis have been applied to evaluate the feasibility, development accuracy and enhancement efficacy of the proposed electrochemical system. The qualitative and quantitative analysis on the in situ and ex situ fingerprint images indicates that the three levels of fingerprint features can be precisely developed and effectively enhanced. Forensic DNA typing has also been performed to reveal actual impact of the proposed electrochemical system on subsequent analysis of touch DNA in fingerprint residues. The ratio of detected loci after electrochemical treatment reaches up to 98.5 %, showing non-destructive nature of this fingerprint development and enhancement technique.

State‐of‐the‐art CO2 reduction in electrochemical microfluidic systems: A short review and new perspectives

The need to mitigate carbon dioxide has motivated an influx of interest in innovative technologies, and microfluidic systems have emerged as a promising forefront in this endeavor. This short review analyzes CO2 reduction within microfluidic platforms, thoroughly investigating existing methodologies, challenges, and novel perspectives. This work commences with a detailed exposition of the fundamental principles governing microfluidic electrolyzers, elucidating the interaction of microchannels and electrodes. We show the electrochemical reactions supporting CO2 reduction, detailing the processes at the cathode. The use of microfluidic systems encompasses precise control over reaction conditions, efficient mass transport, reduced energy consumption, high throughput screening capabilities, integration with analytical tools, and portability. Catalyst selection for optimal CO2 reduction products, technical complexities, integration of renewable energy sources, and cost‐effectiveness are notable challenges on the horizon. A perspective on potential pathways to resolution is delineated, with each impediment succinctly but insightfully addressed. Moreover, this review extends beyond a looking‐back analysis, propounding innovative perspectives. It posits the concept of microfluidic fuel cells directly fueled by CO2. This work seeks to inspire new researchers and innovation in the field by comparing the present state‐of‐the‐art with prospective avenues of exploration

Probing Electronic Structure Changes in Cobalt Oxalate Anode for Lithium‐Ion Batteries

AbstractTransition metal‐based materials exhibit a broad range of catalytic activities in numerous electrochemical processes. Their displayed catalytic functions rely essentially on their distinctive electronic structures, changes of which play pivotal roles in dictating reaction dynamics within many electrochemical devices. Nevertheless, accurately probing electronic structure changes, especially in real‐time, of active materials remains a formidable challenge. In this work, a viable approach to achieve it within a CoC2O4/Li model system by employing a combined microscopic is demonstrated, spectroscopic analysis, plus a unique operando magnetometry technique. The findings reveal that upon completion of the conventional conversion of CoC2O4, a surface‐dominated capacitance emerges at the Co/Li2C2O4 interface owing to the injection of spin‐polarized electrons. Subsequently, the decomposition of Li2C2O4 proceeds through the releasing of the spin‐polarized electrons from Co, which, therefore serve as a catalyst leading to further discharge products. Such real‐time monitoring of electron transfer is realized by in situ monitoring electronic structure changes of Co, manifested by its intriguing magnetization alterations during the process. This work highlights a novel characterization tool that provides a solid explanation for the commonly observed large capacities in this type of materials and sheds light on design rules and selection guidance of materials for high‐performance electrochemical energy storage systems.

Redox-Modified Nanostructured Electrochemical Surfaces for Continuous Glucose Monitoring in Complex Biological Fluids.

Continuous glucose monitoring is valuable for people with diabetes but faces limitations due to enzyme-electrode interactions and biofouling from biological samples that reduce sensor sensitivity and the monitoring performance. We created an enzyme-based electrochemical system with a unique nanocomposite coating that incorporates the redox molecule, aminoferrocene (NH2-Fc). This coating enhances stability via electroactivity and reduces nonspecific binding, as demonstrated through cyclic voltammetry. Our approach enables real-time glucose detection via chronoamperometry with a calculated linear range of 0.5 to 20 mM and a 1 mM detection limit. Validated with plasma and saliva, this platform shows promise for robust metabolite detection in clinical and research contexts. This versatile platform can be applied to accurately monitor a wide range of metabolites in various biological matrices, improving patient outcomes.

Differential Impact of Surface Conduction and Electroosmotic Flow on Ion Transport Enhancement by Microscale Auxiliary Structures.

Our research investigates the impact of auxiliary structures on ion transport in electrochemical systems such as batteries and microscale desalination units, whose importance for sustainable development has increased dramatically in recent decades. The electrochemical systems typically feature ion-selective surfaces, such as electrodes and ion exchange membranes, where ion depletion can cause performance issues including metal dendrite formation and flow instability. Recent research has shown that auxiliary structures in these electrochemical systems can enhance ion transfer near ion-selective surfaces, thereby resolving the instability problem and improving the energy conversion efficiency of the system. Our study leverages recent advancements in nanoscale electrokinetics to model these auxiliary structures as pillar arrays near an ion exchange membrane in a microchannel. We examine how these structures enhance ion transports relative to the characteristic length scale of microchannel depth and pillars' proximity to the ion-selective surface. Results show that the effect of the pillars varies significantly with their placement. Specifically, in deeper microchannels, where electrokinetic convection is stronger, the closer the auxiliary structure is to the ion-selective membrane, the better the ion transfer. However, in the thinner microchannel, the proximity of the auxiliary structure to the ion selective membrane has a less significant correlation with the ion transfer. Therefore, this finding highlights the importance of spatial arrangement of the auxiliary structures in improving the performance of electrochemical devices. Conclusively, this study can help to better understand energy conversion systems such as fuel cells, salinity gradient power generation systems, and electrochemical desalination systems, where auxiliary structures can be used in the vicinity of ion-selective surfaces. Especially, our fundamental electrokinetic study provides an effective means for designing the efficient electrochemical platforms utilizing micro/nanofluidics.

Comparative study on the thermal runaway characteristics of Li(NixCoyMnz)O2 batteries

Lithium-ion batteries (LIBs) generate substantial gas during the thermal runaway (TR) process, presenting serious risks to electrochemical energy storage systems in case of ignition or explosions. Previous studies were mainly focused on investigating the TR characteristics of Li(NixCoyMnz)O2 batteries with different cathode materials, but they were conducted in isolation. In this study, the thermal runaway characteristics of prismatic cells that use Li(NixCoyMnz)O2 (with x ranging from 0.33 to 0.9) cathode materials in an inert environment, which are commonly used or proposed for energy storage applications, are examined. The findings of this research show that the normalized gas generation rate remains consistent, regardless of the battery capacity or experimental chamber volume, with a value of 0.1 ± 0.03 mol∙Ah⁻1. High-capacity cells have short jetting durations, and a high nickel content leads to increased mass loss rates. The flammability limits of the gases expelled during thermal runaway, represented by the lower flammability limit (LFL), remain stable at 8 ± 1.8% with minimal variations. However, the upper flammability limit (UFL) varies significantly, ranging from 30% to 60%. Increasing the battery capacity or reducing the experimental chamber volume increases the explosion index. The explosive, combustibility, and jetting duration characteristics of the emitted gases from five different battery chemical compositions provide valuable insights for risk assessment in future electrochemical energy storage systems.

Surface Reconstruction for Selective Oxidation of Tetrahydroisoquinoline.

Integration of hydrogen evolution with the oxidation of organic substances in one electrochemical system is highly desirable. However, achieving selective oxidation of organic substances in the integrated system is still highly challenging. In this study, a phosphorylated NiMoO4 nanoneedle-like array was designed as the catalytic active electrode for the integration of highly selective electrochemical dehydrogenation of tetrahydroisoquinolines (THIQs) with hydrogen production. The leaching of anions, including MoO42- and PO43-, facilitates the reconstruction of the catalyst. As a result, nickel oxyhydroxides with the doping of PO43- and richness of defects are in situ formed. In situ Raman and density functional theory calculations have shown that the high catalytic activity is attributed to the in situ formed PO43- involved NiOOH substance. In the dehydrogenation process, the involved C-H bond but not the N-H bond is first destroyed. A two-electrode system was then fabricated with the optimized electrode that shows a benchmark current density of 10 mA cm-2 at 1.783 V, providing a yield of 70% for dihydroisoquinolines. A robust stability was also shown for this integrated electrochemical system. The understanding of the reconstruction behavior and the achievement of selective dehydrogenation will provide some hints for electrochemical synthesis.