High Ion Concentration Research Articles

Quality of Surface and Groundwater in the Sierra de Amula Region, Jalisco, Mexico

Water is a valuable natural resource, indispensable in the productive, economic, and social development of human beings, agriculture, and domestic and industrial uses throughout the world. Two samplings were established to evaluate the quality of surface and underground water for agricultural irrigation in the Sierra de Amula Region, Jalisco, Mexico. The first was performed during the dry season from November 2021 to April 2022, and the second was performed during the rainy season from July to September 2022 through completely random probabilistic sampling and a longitudinal descriptive study. In total, 25 surface water and 30 groundwater samples were taken. Each sample was evaluated for its pH, electrical conductivity, and ionic concentration (Ca2+, Mg2+, Na+, K+, CO32−, HCO3−, CI−, SO42−). For data analysis, we determined the ionic concentrations and the salinity and sodicity indexes, including the electrical conductivity, pH, sodium adsorption ratio (SAR), and cationic ratio of soil structural stability (CROSS). The results indicate that the ionic concentration is mainly due to calcium bicarbonate, probably due to the geology of the region through water–rock interactions, and the pH is between 6.64 and 7.77; with respect to EC, most of the sampled sites are concentrated in medium-salinity waters of 250–750 µS cm−1. The sodium adsorption ratio (SAR) showed that the waters have high ionic concentrations of calcium and magnesium and low sodium. The CROSS values were lower than the SAR values, showing that the concentration of potassium ions K+ is low in the evaluated waters. With respect to salinity and sodicity, the water quality of the sampled sites, both surface and groundwater, can be considered good for agricultural use. Given that it was sampled in two seasons, the concentration of ions varies in the rainy season, with the dragging of materials causing the ions to concentrate to a greater extent. This type of research benefits farmers in reducing production costs, having knowledge of water quality, and decision making. We recommend that the alkaline pH of the surface or groundwater be conditioned according to the requirements of the crop to be grown and the irrigation method to be used.

Characterisation of galvanisation effluent using lime-anionic polyacrylamide: A case study from Gauteng, South Africa

 Galvanisation, a critical industrial process for rust prevention, generates effluents containing heavy metals and other pollutants, posing environmental and health risks. This study evaluates the effectiveness of a combined lime- anionic polyacrylamide (PAM) treatment to reduce these contaminants from effluent generated by the galvanising industry in Gauteng, South Africa. Effluent samples were collected and analysed for heavy metals (Cd, Cr, Cu, Pb, Zn, Mn, Fe) and physicochemical parameters, including electrical conductivity, chloride, and pH, using standard methods. Untreated effluent exhibited high levels of heavy metals, particularly lead, zinc, manganese, and iron, far exceeding local discharge limits. Post-treatment analysis showed substantial reductions in metal concentrations, achieving compliance with regulatory standards, with pH-adjusted to optimal levels for metal hydroxide precipitation. Additionally, chloride concentrations were reduced from 14,383.24 mg∙dm−3 to 3,890.40 mg∙dm−3 and electrical conductivity from 130.50 to 21.10 μS∙cm−1. Despite these improvements, the values still exceeded the municipality’s discharge limits of 500 mg∙dm−3 for chloride and 0.1 μS∙cm−1 for conductivity, indicating residual high ion concentrations. While the lime-PAM treatment effectively improved effluent quality, the results suggest a need for supplementary treatments to achieve full compliance with stringent regulatory standards. Overall, the lime-PAM approach shows potential for reducing heavy metals and physicochemical contaminants reduction in galvanising effluent. However, further optimisation and integration of advanced treatment technologies are recommended to enhance efficacy and ensure environmental compliance.

Ferro-ionic states and domains morphology in HfxZr1−xO2 nanoparticles

Unique polar properties of nanoscale hafnia-zirconia oxides (HfxZr1−xO2) are of great interest for condensed matter physics, nanophysics, and advanced applications. These properties are connected (at least partially) to the ionic–electronic and electrochemical phenomena at the surface, interfaces, and/or internal grain boundaries. Here, we calculated the phase diagrams, dielectric permittivity, spontaneous polar, and antipolar ordering, as well as the domain structure morphology in HfxZr1−xO2 nanoparticles covered by ionic–electronic charge originating from surface electrochemical adsorption. We revealed that the ferro-ionic coupling supports the polar long-range order in nanoscale HfxZr1−xO2, induces, and/or enlarges the stability region of the labyrinthine domains toward smaller sizes and smaller environmental dielectric constant at low concentrations of the surface ions. The ferro-ionic coupling causes the transition to the single-domain ferro-ionic state at high concentrations of the surface ions. We predict that the labyrinthine domain states, being multiple-degenerated, may significantly affect the emergence of the negative differential capacitance state in the nanograined/nanocrystalline HfxZr1−xO2 films.

Hydrogen Bonding-Driven Adaptive Coacervates as Protocells.

Coacervation based on liquid-liquid phase separation (LLPS) has been widely used for the preparation of artificial protocells and to mimic the dynamic organization of membrane-free organelles. Most complex synthetic coacervates are formed through electrostatic interactions but cannot withstand high ionic strength conditions (>0.1 M). Alternative components and driving forces are highly desired for the formation of natural organelles to overcome the drawbacks of traditional coacervates. Herein, hydrogen bonding-driven adaptive coacervates are reported via the complexation of poly(ethylene glycol) (PEG) and tannic acid (TA). The LLPS behavior of these adaptive coacervates is dependent on the concentration and mass ratio of PEG and TA, which can be used to tune the size of coacervates ranging from 70 nm to 10 μm as well as the morphology of isotropic particles and hollow capsules. Coacervates are stable at high ionic concentrations up to 1 M and can serve as protocells to mimic cellular behaviors including metabolism (e.g., nutrient uptake), phagocytosis, and membrane fusion. The reported approach provides a platform for the rational design of hydrogen bonding-driven coacervates with controllable size and morphology, offering potential applications in protocell construction and therapeutic delivery.

An observed "sandwich" framework mediated via sulfate ions as electron shuttle for efficient electro-oxidation of organic pollutants.

"Electro-oxidation processes are effective in treating sulfate-rich organic wastewater. However, this technology development has been hindered by the poor understanding of the role of sulfate ions. This paper reports that high concentration of sulfate ions significantly enhanced the electro-oxidation of organic pollutants. High sulfate concentration did not affect radical activity or organic pollutant coverage on the electrode surface. We propose that the electrode interface forms a "sandwich" framework mediated by sulfate ions, consisting of the electrode surface, the sulfate ion layer, and the organic pollutant layer. High concentrations of sulfate ions selectively promote the protonated organic pollutant into the framework via electrostatic attraction when the solution pH is lower than the pKa of the organic pollutants. In this framework, the sulfate ion layer acts as an electron shuttle, creating a smooth electron transfer pathway between the electrode surface and the organic maters. In this way, the "sandwich" framework can efficiently electro-oxidize organic pollutants. This study offers new insights into the role of sulfate ions in electro-oxidation processes, redefining their role in pollutant degradation, and guiding the design of sulfate-rich wastewater treatment."

Insight into the roles of Cl− for the degradation of acid Red 14 in an electrochemical advanced oxidation system: Mechanisms and DFT studies

Textile wastewater was typically characterized by high concentrations of chloride ions, with Acid Red 14 (AR14) representing a significant pollutant. Nevertheless, research into the degradation of AR14 by electrochemical advanced oxidation processes (EAOPs) had largely overlooked the influence of chloride ions. In this regard, the EC-Clorine-MMO/Ti system was designed, and the degradation mechanism of AR14 was subjected to meticulous investigation. The adopted anode was composed of Ti/IrO2-Ta2O5 (mixed metal oxide, MMO). It demonstrated superior efficiency in degrading AR14 within a sodium chloride (NaCl) electrolyte, registering an apparent kinetic constant rate approximately 16.76 times greater than that observed within a sodium perchlorate (NaClO4) electrolyte. The optimal chloride ion concentration was identified as 0.04 mol/L. Besides, alkaline conditions were not conducive to the degradation of AR14. It was noteworthy that the electrochemical byproducts chlorite (ClO2−), chlorate (ClO3−), perchlorate (ClO4−), and trihalomethane (THMs) were not produced in the solution treated by the EC-Clorine-MMO/Ti system. Electron paramagnetic resonance (EPR) spectroscopy, probe, and quenching experiments identified that hydroxyl radicals (•OH), superoxide radicals (O2•−), and dichloride radicals/chlorine monoxide radicals (Cl2•−/ ClO•) were the major reactive species. Of these, •OH played a pivotal role in AR14 degradation. Additionally, the three principal degradation pathways of AR14 were deduced by LC-MS analysis, UV–vis spectra, density-functional theory (DFT) calculations, and excitation-emission matrix (EEM) fluorescence spectroscopy. Furthermore, the generation mechanism of reactive species and the proposed mechanism of AR14 degradation by the EC-Clorine-MMO/Ti system were presented. The study made a significant contribution to the understanding of the electrochemical reactions occurring in textile wastewater and provided valuable insights into the rational control of electrolytic conditions for the treatment of saline wastewater.

A cost-effective and innovative detector for iron ions.

Severe environmental contamination can result from high concentrations of iron ions, which can have a detrimental impact on human health and well-being. Consequently, it is imperative to develop novel materials that can address environmental issues. Metal-organic frameworks (MOFs) possess unique properties that render them efficient fluorescent probes for the rapid and precise detection of these pollutants. A diverse array of MOF probes have been developed to detect iron ions. Nevertheless, their practical application is significantly impeded by the high production cost, which is a critical factor. This raises the question: why not implement a cost-effective, sensitive detector instead? Our research group has developed a novel MOF material, [Zn2(bpy)(APA)2(H2O)] n , that is specifically designed for MOF-based "off" sensors in aqueous media. This material not only demonstrates high sensitivity, and is manufactured from low-cost raw materials, but it also holds significant commercial potential, with production costs that are 98.4% lower than those of existing alternatives.

Electrochemical-thermal-mechanical overcharge model on a scale of particle for lithium-ion batteries

During overcharging of lithium-ion batteries, lithium plating can occur on the anode surface when the maximum lithium intercalation concentration is exceeded, while the cathode is in a lithium-poor state, which can result in shortened battery lifespan and safety. In this work, the geometric structure of the positive electrode particles is designed based on the tomography data, while the negative electrode particles are represented by spheres with different sizes. The homogenization method is used, with the carbon filler, binder and electrolyte regarded as a single porous conductive adhesive domain. Based on the main mechanism of lithium-ion battery overcharge, a coupled three-dimensional electrochemical-mechanical-thermal overcharge model on a particle scale is developed for NCM cathode and graphite anode. The coupled mathematical model consists of four parts, namely the electrochemical model, the lithium plating model, the thermal model and the stress-strain model. In terms of lithium precipitation, the particle radius parameter and charging rates are investigated. The results show that the lithium plating concentration of the particles near the separator is higher, following the “principle of proximity” , namely the sequence of lithium deintercalation is related to the migration path. The surface of anode particles with small particle size is more prone to lithium precipitation due to the high maximum lithium ion concentration on the surface of the particles, the low surface lithium precipitation overpotential, and the high average Von Mises stress. At high charging rate, fast charge transfer rate and ion diffusion rate result in a low voltage at the anode, triggering off lithium precipitation. At a low rate, polarization and low temperature can lead to the precipitation of more lithium on the surface of the anode particles. In terms of stress, the spatial distribution between particles and thermal effects are investigated. The ratio of the distance from the contact surface to the center of the particle to the particle radius is calculated and defined as the contact depth (<inline-formula><tex-math id="M2">\begin{document}$Jr$\end{document}</tex-math></inline-formula>), in order to better describe the law of particle contact stress. It is shown that the contact depth between particles is inversely proportional to the stress on the contact area. When the heat generation effect is considered, the temperature of the battery rises faster with the increase of the charging rate. The electrochemical parameters related to temperature and the lithium concentration diffusion gradient increase significantly, and the influence of temperature on the particle stress is also more significant. The relevant results can provide theoretical basis and guidance for designing battery and optimizing charge strategies.

A robust and conductive hydrotalcite/nanocellulose/PVA hydrogel constructed based on the Hofmeister effect.

Conductive hydrogel is one of the basic materials for constructing flexible sensors, and polyvinyl alcohol (PVA) hydrogel is commonly used. However, the current PVA hydrogels have apparent defects in strength and conductivity. The freeze-salting-out process based on the Hofmeister effect can effectively improve the strength of PVA. This study uses hydrotalcite and nanocellulose as additives to construct PVA composite hydrogel using the freeze-salting-out method. Due to the reconstruction of the hydrogen bond and the construction of a multi-level three-dimensional network structure, the tensile strength and elongation of PVA composite hydrogels are improved to 8.2 times and 8.1 times that of the pure PVA hydrogels, respectively. Meanwhile, the conductivity of PVA composite hydrogel is increased by 6.4 times with the significant development of ion content and the effective establishment of the transport path. Based on the characteristics of high ion concentration and stable network structure, the composite hydrogels show excellent elastic and strain recovery properties at -20°C and room temperature. The prepared composite hydrogels have good biocompatibility. This work realizes the construction of PVA composite hydrogel material with high strength, high conductivity and wide temperature application range. It provides a new idea for the development of flexible biosafety sensors.

Impact of Wood Smoke Exposure on Aortic Valve Mineralization: Microvesicles as Mineral Conveyors in Patients with Coronary Stenosis.

Background: Aortic valve calcification results from degenerative processes associated with several pathologies. These processes are influenced by age, chronic inflammation, and high concentrations of phosphate ions in the plasma, which contribute to induce mineralization in the aortic valve and deterioration of cardiovascular health. Environmental factors, such as wood smoke that emits harmful and carcinogenic pollutants, carbon monoxide (CO), and nitrogen oxide (NOx), as well as other reactive compounds may also be implicated. The purpose of this research was to study the impact of wood smoke on specific aortic valve characteristics, including lesion size and percentage of mineralization, in patients with aortic valve stenosis (AS). Methods: This observational study included 65 patients who underwent primary valve replacement surgery at the National Institute of Cardiology, 11 of whom were exposed to wood smoke. For each patient, approximately 0.5 cm of aortic valve tissue was collected along with a blood sample anticoagulated with sodium citrate. The valves were analyzed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). Since extracellular microvesicles (MVs) may induce epigenetic changes in target cells by transferring their cargo, we also analyzed their mineral content. Results: Individuals exposed to wood smoke exhibit more extensive lesion (835 µm2) characteristics compared to those with no exposure (407.5 µm2). Interestingly, FESEM images of MVs showed the presence of minerals on their surface, thus providing evidence on their possible role in the pathophysiology of mineralization. Conclusions: Our study uniquely demonstrates imaging-based evidence of structural damage and mineralization in aortic valve tissue, with chronic wood smoke exposure emerging as a significant causative factor.

MODEL OF A CONCRETE SYSTEM WITH INTERNAL HYDROPHOBIC FUNCTIONALIZATION AND SUPERHYDROPHOBIC COATINGS WITH LONG-TERM STABILITY

Cement and concrete are indispensable basic materials for national economic construction and social development, have a wide application and will continue to play a central role in the production of building materials in the future. However, their durability crisis is becoming increasingly noticeable due to the inherent characteristics of the material and external environmental factors, which poses a serious challenge to the sustainable growth of the construction industry. In particular, the concept of “long-term building service life” is proposed specifically to meet the basic strategic needs of national security and sustainable development. It is relevant to severe operating conditions (carbonation, chloride aggression, freeze-thaw cycle, wet-dry), safe operation and maintenance, where increased requirements are placed on the durability of structural concrete. Researching practical and effective technologies to improve durability is an important task to be solved at this stage. The porous structure of concrete and the metastable properties of hydration products are the cause of deterioration of its performance characteristics at later stages. Structural looseness refers to the presence of loose transition interfaces in concrete. They consist of weak interfaces caused by excessive accumulation of water on the surface of aggregates and steel rods, as well as interface defects arising due to significant orientation of Ca(OH)2 and weak forces of interlayer bonding. Porosity is the formation of pores during the preparation, construction, and hydration of cementitious materials. The density of the microstructure of concrete is primarily affected by the uneven space formed as a result of the consumption or evaporation of water during mixing. Metastability refers to the phenomena of dissolution, carbonation, and transformation occurring in the hydration products of cement, which can cause changes in the volume of concrete and subsequently impact its durability. Harsh environmental conditions can significantly modify the durability of concrete, especially in environments with high concentrations of corrosive ions, such as marine environments, freeze-thaw cycles, and hot and humid wetting-drying cycles. It was noted by the founders of concrete corrosion science that “the permeability or impermeability of concrete is a characteristic directly related to durability.” However, cement-based materials are inherently porous and metastable. This makes traditional engineering approaches, such as compaction, difficult to inhibit water-salt transport over the long term, resulting in reduced durability. In recent years, the application of hydrophobic modification technology for corrosion protection has attracted considerable attention due to its relationship with the theory of “lotus leaf effect”. This approach opens up new prospects for effectively improving the durability of cement concrete.

Crack Sealing in Concrete with Biogrout: Sustainable Approach to Enhancing Mechanical Strength and Water Resistance.

Concrete, as the most widely used construction material globally, is prone to cracking under the influence of external factors such as mechanical loads, temperature fluctuations, chemical corrosion, and freeze-thaw cycles. Traditional concrete crack repair methods, such as epoxy resins and polymer mortars, often suffer from a limited permeability, poor compatibility with substrates, and insufficient long-term durability. Microbial biogrouting technology, leveraging microbial-induced calcium carbonate precipitation (MICP), has emerged as a promising alternative for crack sealing. This study aimed to explore the potential of Bacillus pasteurii for repairing concrete cracks to enhance compressive strength and permeability performance post-repair. Experiments were conducted to evaluate the bacterial growth cycle and urease activity under varying concentrations of Ca2+. The results indicated that the optimal time for crack repair occurred 24-36 h after bacterial cultivation. Additionally, the study revealed an inhibitory effect of high calcium ion concentrations on urease activity, with the optimal concentration identified as 1 mol/L. Compressive strength and water absorption tests were performed on repaired concrete specimens. The compressive strength of specimens with cracks of varying dimensions improved by 4.01-11.4% post-repair, with the highest improvement observed for specimens with 1 mm wide and 10 mm deep cracks, reaching an increase of 11.4%. In the water absorption tests conducted over 24 h, the average mass water absorption rate decreased by 31.36% for specimens with 0.5 mm cracks, 29.06% for 1 mm cracks, 27.9% for 2 mm cracks, and 28.2% for 3 mm cracks. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the formation of dense calcium carbonate precipitates, with the SEM-EDS results identifying calcite and vaterite as the predominant self-healing products. This study underscores the potential of MICP-based microbial biogrouting as a sustainable and effective solution for enhancing the mechanical and durability properties of repaired concrete.

Destruction Of C7, C9 Perfluorocarboxylic Acids By The Strain Ensifer Adhaerens M1

The aim of the study was to determine the resistance to high concentrations of fluoride ions in the environment of the strain Ensifer adhaerens M1 isolated from soil at a fire extinguishing agent storage and testing site, to determine the growth kinetics and destruction of C7, C9 perfluorocarboxylic acids, perfluoroheptanoic acid and perfluorononanoic acid, respectively, as the sole sources of carbon and energy. The degradation products of perfluorinated carboxylic acids were identified using LCMS-IT-TOF. It was found that the degradation process occurs in multiple stages leading to the formation of perfluorohexanoic acid and accompanied by the release of fluoride ions. Strain Ensifer adhaerens M1 is resistant to F- up to a concentration of 150 mg/L in the environment. Within 14 days of cultivation, bacteria completely utilized perfluoroheptanoic acid and perfluorononanoic acid. Based on chromatography-mass spectrometry and ion chromatography data, a scheme for the stepwise degradation of the investigated perfluorinated acids involving the enzymes coded by novR and dhlA genes is proposed.

Sustainable supercapacitors using advanced hydrated amino acid ionic liquids: A novel approach to biodegradable energy storage

In this work, we explore the concepts of molecular dynamics (MD) to investigate the energy storage capacity of supercapacitors (SCs) composed of amino acid-based ionic liquids (AAILs) as pure and hydrated electrolytes, and graphene electrodes. The choice to use AAILs is motivated by environmental concerns, as these compounds are biodegradable. We focused our efforts on models composed of 1-ethyl-3-methylimidazolium (emim) combined with alanine (ala), valine (val), leucine (leu), and isoleucine (ile). Furthermore, we aimed to optimize the biodegradable properties by considering different hydration levels of the electrolyte. We analyzed the models subjected to hydration in proportions of 10 %, 20 %, 30 %, 40 %, and 90 %. This research addresses the lack of detailed studies on the effect of hydration on AAIL electrolytes in supercapacitors, evaluating their impact on energy storage and electric double layer (EDL) formation, and highlights the potential of AAILs as electrolytes for supercapacitors, offering a biodegradable option for energy storage without a loss of efficiency. The results obtained showed capacitances between 2.29 and 2.71 µF/cm2, and gravimetric energy densities ranging from 4.4 to 4.8 J/g for electrolytes with high ion concentrations, and from 6.5 to 6.8 J/g for devices with low ion concentration electrolytes. These values indicate excellent potential for application in the context of energy storage, reinforcing the viability of AAILs as an environmentally friendly and efficient solution for supercapacitors.

The effect of ion solvation on ion-induced nucleation—A generalized Thomson model

We present a model for ion-induced nucleation, focusing on the effect of dissociated ions embedded in the fluid surrounding a charged core or colloid. The model includes the ions' direct electrostatic energy and preferential solvation. The integrated ions' free energy has two terms: The first can be short- or long-range, depending on their density. The second is proportional to the nucleus' volume and can shift the state from undersaturation to supersaturation at high ion concentration. The inclusion of the Gibbs transfer energies of ions in the free energy leads to a modified Poisson-Boltzmann equation for the potential around the core. The integrated ions' free energy is added to the fluids' interfacial and bulk terms to establish a generalized Thomson model. In the Debye–Hückel limit, the model is solved analytically, while in the nonlinear regime, it is solved numerically. The state diagram in the plane of saturation and core charge includes regions with a homogeneous phase, electro-prewetting, metastable vapor, metastable nucleus, and spontaneous nucleation states. The lines separating these regions depend sensitively on the preferential solvation. Our model shows nucleation asymmetry to the sign of the nucleus' charge. This sign asymmetry is due to the Gibbs transfer energies of ions.

Novel cationic and amphoteric starch-modified coagulants for efficient treatment of relatively high turbidity and large organic matter source waters: Performance, predictive modeling and mechanism analysis

Finding alternative solutions of water source containing short-term relative high turbidity and large organic content is a pressing need in view of the inherent limitations of traditional inorganic coagulants. Requirement of significant dosage increase for conventional iron and aluminum salt coagulants can create several challenges including dose adjustment, suboptimal performance and high concentration of residual metal ions. In this study, acrylamide monomer (AM) and methacryloyloxyethyltrimethylammonium chloride (DMC) were grafted onto starch and carboxymethyl starch to obtain novel cationic and amphoteric starch-modified coagulants. Concurrently, the obtained coagulants were comprehensively evaluated under varying simulated water quality conditions to analyze their turbidity and organic matter removal efficiencies. Polymerized aluminium chloride (PACl) was used as the reference coagulant to evaluate the roles of polymer charge density, total charge, and molecular chain length in the coagulation mechanism for further illustration of their efficacy. In comparison to the traditional coagulant PACl, the modified coagulant was found to be more effective in enhancing flocculation and aggregation behavior, lowering of energy barriers, and enhancing adsorption energy by using the Density Functional Theory (DFT) calculations and Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory based investigation of the mechanism. Moreover, these behaviors were mainly attributed to significant exchange of charge density between coagulant and the pollutants. Additionally, in order to facilitate accurate and efficient treatment of water having diverse qualities, quadratic polynomial equation based mathematical model was constructed for quantitative analysis and model prediction. Findings of this study point towards an effective and precise approach to coagulation technology and thereby enabling sustainable and efficient purification of turbid source water containing large organic matter.

Stability and structure of aqueous Sb (III) chloride complexes from 25 °C to 250 °C at 25 MPa at high chloride ion concentrations

Stability and structure of aqueous Sb (III) chloride complexes from 25 °C to 250 °C at 25 MPa at high chloride ion concentrations

Co-Ion Identity Affects Double Layer Structure and Reactivity Trends in the Hydrogen Evolution Reaction

The formation of an electric double layer is ubiquitous in electrolytes undergoing electrochemical reactions. Currently, models for the double layer rely on the assumptions of dilute electrolyte theory where ions in solution do not interact. Dilute electrolyte theory predicts that solely hydrated counterions, or ions opposing the surface charge, occupy the near surface region and impact reactivity. Since this theory does not account for conditions like high applied potentials and high ion concentrations, understanding the relationship between double layer structure and electrochemical reactivity is critical for opening new domains for electrochemical modulation.Notably, our recent work shows that co-ions, or ions with the same charge as the surface, can also have a definitive influence on reaction rates, particularly under conditions of high applied potential and large bulk ion concentrations. In this talk, I will discuss how to use the hydrogen evolution reaction as a model system to explore co-ion effects in electrocatalytic reactions. In our work, we systematically vary co-ion identity and track hydrogen evolution reactivity as a function of concentration to highlight how the co-ion becomes increasingly relevant in the concentrated regime. In particular, we highlight the unique ability of the tetrafluoroborate co-ion to undergo dynamic ligand exchange between hydroxide and fluoride. This allows tetrafluoroborate to act as a hydroxide sink to stabilize the hydrogen evolution byproduct. Furthermore, I will discuss our use of Raman spectroscopy to describe how co-ions impact interfacial hydrogen bonding networks, which can have a significant impact on aqueous electrochemistry. Our results highlight how co-ions influence double layer structures and have significant implications for tuning other aqueous reactions such as carbon dioxide and nitrate electroreduction.

Quantification and Correction of Impedance Effects on Square Wave Voltammetry for High-Concentration Soluble-Soluble Reactions

Molten salts are of interest for a wide variety of applications including nuclear energy, metal electrorefining, and concentrated solar power. In situ monitoring of species within molten salts is important to ensure operation is well-controlled. Electroanalytical techniques such as square wave voltammetry (SWV) and linear sweep voltammetry (LSV) offer approaches toward precise measurement of species’ fundamental properties (e.g. diffusion coefficient, number of electrons transferred, etc.). However, several publications have reported deviations between data collected through SWVs and LSVs. In this talk, we explain the discrepancy in the context of SWV using molten chloride systems with dissolved metal ions. Theoretical simulations coupled with experimental data confirm the divergence of property measurements can be attributed to impedance effects. Using our approach, the diffusion coefficients, solubility limits, and concentration measurements at high concentrations of metal ions extracted using SWV converged with literature reports using LSVs.

An ultra-low fouling electrochemical mocularly imprinted sensor based on size exclusion effect for highly selective pentachlorophenol detection

Pentachlorophenol (PCP) is considered as a highly toxic pollutant in water environment. However, detecting low concentrations of PCP precisely hindered by various interferences is still a tough challenge. In this study, an antifouling electrochemical molecularly imprinted (E-MIP) sensor harnessing the size exclusion effect was specifically designed for highly selective detection of PCP in water. The distinctive interaction between the size-selective poly-hydroxyproline helical peptide (PHHP) and poly(o-phenylenediamine) (p(o-PD)) molecularly imprinted films, strongly reduced non-specific adsorption. In the face of high concentrations of organic matters and ions, the reported sensor exhibited robust antifouling capabilities that it preserved 90 % of the initial signal. In addition, the limit of detection (LOD) reached an exceptionally low level of 1.13 nM (S/N = 3), spanning a wide linear range from 1 nM to 10 μM, and the sensor showed high selectivity with an impressive imprinted factor of 12.01 for PCP. Meanwhile, it owned great repeatability and reproducibility, long-term stability for PCP detection within 25 days, and decent reusability (retaining 92.33 % of its senor performance after 5 cycles), which ensured its excellent feasibility for determination of PCP in complex water samples with co-existing interferences due to acceptable recoveries. The development of this strategy provides an innovative platform for PCP quantification in real water samples, underscoring its potential as a key tool in managing PCP at relevant sites.