Electrode Surface Research Articles

Monitoring the Solid-Electrolyte Interphase Formation in Bis(fluorosulfonyl)Amide Ionic Liquid Electrolyte Using a Redox Probe Method

The solid-electrolyte interphase (SEI) has been considered to be formed on the negative electrode surface by reductive decomposition of electrolyte components. In the case of the electrolytes containing lithium ions, the SEI can be regarded as the Li+ conductor that enables the negative electrode reactions and prevents the further decomposition of the electrolytes. The structure of the SEI is often explained by the mosaic model, in which the SEI is a composite of several different inorganic and organic domains [1]. On the other hand, we have proposed the formation of the gelled SEI in bis(fluorosulfonyl)amide (FSA–) ionic liquid electrolytes containing a high concentration of LiFSA [2,3]. Furthermore, we have reported that the SEI formation can be detected by monitoring the redox reaction of ferrocene (Fc) and ferrocenium (Fc+) [4,5]. In the present study, the time-dependent transition of the SEI formed on a Pt electrode was investigated by the redox probe method in BMPFSA (BMP+ = 1-butyl-1-methylpyrrolidinium) containing LiFSA.The formation of SEI by holding a Pt electrode at a negative potential was confirmed by a shift in the anodic peak potential of the cyclic voltammogram for Fc+/Fc couple in LiFSA/BMPFSA. The anodic peak disappeared when the electrode was held at the negative potential for a few hours, indicating the formation of a thick SEI. However, the anodic peak was observed again after keeping the electrode at the open circuit potential for a few hours, indicating the disappearance of the SEI. These results suggest that the SEI is formed by dissolution and/or dispersion of the decomposed products, which form at the electrode surface and diffuse into the electrolyte. Thus, the SEI formed at the potential is considered to exist as a metastable phase in the balance between the formation and diffusion of the decomposition products. This work was partly supported by GteX Program Japan Grant Number JPMJGX23S0.[1] E. Peled, D. Golodnitsky, and G. Ardel, J. Electrochem. Soc., 144, L208 (1997).[2] R. Furuya, T. Hara, T. Fukunaga, K. Kawakami, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 168, 100516 (2021).[3] N. Serizawa, R. Yamashita, and Y. Katayama, J. Phys. Chem. C, 127, 10434 (2023).[4] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 169, 076509 (2022).[5] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 170, 056504 (2023).

The Effects of Temperature and Fluoroethylene Carbonate Concentration on the Formation of the Graphite SEI and Its Impact on the Full-Cell Performance

Extending the cycle-life of state-of-the-art lithium-ion batteries (LiBs) is, amongst other aspects, predicated on optimizing the properties of the solid electrolyte interphase (SEI), such as its stability and resistance.[1] It is formed at the negative electrode during the first cycles by electrolyte decomposition and acts as a passivating layer between the electrode surface and the electrolyte.[2,3] Since the SEI formation is accompanied by an irreversible loss of cyclable lithium, its stability during cycling is crucial for improving the charge/discharge efficiency of LiBs. Furthermore, the arising resistance associated with the SEI formation, predominantly depending on the SEI thickness, its chemical composition, and its lithium-ion conductivity, all impact the rate performance of the anode.[4] Two of the most crucial factors impacting SEI formation are temperature and electrolyte composition (i.e., using electrolyte additives).[5] Additives are added to the electrolyte to inhibit the predominant reduction of other electrolyte constituents and thereby form an SEI with improved stability during cycling.[1,6,7] One of the most prominent additives for LiBs is fluoroethylene carbonate (FEC), which is preferentially reduced compared to common carbonate solvents (e.g., ethylene carbonate, ethyl methyl carbonate) due to its higher reduction potential.[7] In this study, we investigated the influence of the formation temperature between 10 and 60 °C, as well as the concentration of FEC (2 and 20 %wt in EC:EMC 3:7 wt/wt with 1 M LiPF6, Gotion, USA) on the characteristics of a synthetic graphite (SMG-A5, Resonac, Japan) anode, both in SMG/Li half-cells and in Ni-rich NCM/SMG full cells.We quantified the first-cycle irreversible capacity loss (ICL) in SMG/Li half cells with a lithium reference electrode after two 0.1 C formation cycles and compared the FEC containing electrolytes to the baseline- (LP-57) and an LP-572 (1 M LiPF6 in EC:EMC 3:7 wt/wt + 2 %wt vinylene carbonate (VC), Gotion, USA) electrolyte. Employing electrochemical impedance spectroscopy in an SMG/Li half-cell setup with a µ-reference electrode and a free-standing graphite electrode,[8,9] we could further quantify the intercalation resistance (R Int, representing the sum of the charge-transfer and the SEI resistance) after an identical formation protocol at 40 % SOC. Both quantities, the ICL and R Int, increase with increasing formation temperature and higher FEC content.The impact of an increasing R Int on the rate performance was tested in Ni-rich NCM/SMG full cells with a lithium reference electrode, revealing a decreased rate capability and higher susceptibility for lithium plating for cells that were formed at higher temperatures and contained 20 %wt FEC. Additionally, the cycling stability of Ni-rich NCM/SMG full cells at 25 °C was assessed in coin cells. Despite an increased ICL and R Int after formation, cells that were formed at elevated temperatures and contained 20 %wt FEC showed enhanced cycling stability compared to those that were formed at a lower temperature and contained less FEC.Finally, on-line electrochemical mass spectrometry (OEMS) was employed to quantify the evolved gases during the formation of a Ni-rich NCM/SMG full cell containing either of the FEC-containing electrolytes at different temperatures. In accordance with an increased ICL and R Int, a higher formation temperature, as well as a higher FEC content, gave rise to a more pronounced gas evolution during formation.

(Digital Presentation) Temperature-Induced Conversion of 2D Vanadium-Doped MoSe2 Nanosheets to 1D V2MoO8 Rods: Enhanced Performance in Electrochemical Antibiotic Detection in Biological and Environmental Samples

A new strategies were developed to prepare 1D-V2MoO8 (VMO) rods from 2D V-doped MoSe2 nanosheets (VMoSe2) with good control over morphology and crystallinity by a facile hydrothermal and calcination process. The morphological changes from 2D to 1D rods were controlled by changing the calcination temperature from 300 to 600 °C. The elimination of Se and the incorporation of O into the V-Mo structure were evaluated by TGA, p-XRD, Raman, FE-SEM, EDAX, FE-TEM, and XPS analyses. These results prove that the optimization of the physical parameters leads to changes in the crystal phase and textural properties of the prepared material. The VMoSe2 and its calcined products were investigated as electrochemical sensors for the detection of the antibacterial drug nitrofurantoin (NFT). At a calcination temperature of 500 oC, the modified SPCE proved to be an excellent electrochemical sensor for the detection of NFT in neutral media. Under the optimized conditions, VMO-500 oC/SPCE exhibits low LOD (0.015 µM), wide linear ranges (0.1-31, 47-1802 µM), good sensitivity, and selectivity. The proposed sensor was successfully used for the analysis of NFT in real samples with good recovery results. Moreover, the reduction potential of NFT agreed well with the theoretical analysis using quantum chemical calculations, with the B3LYP with 6-31G(d,p) basis set predicting an E 0 value of -0.45 V. The interaction between the electrode surface and NFT via the LUMO diagram and the electrostatic potential surface is also discussed.

Next-Generation Batteries through Advanced 3D Electrode and Material Concepts

With the rise of renewable energy sources, energy storage solutions become increasingly important as they represent a key feature for secure and constant power supply. In this regard, battery systems play a crucial role in accelerating the transition towards sustainable and green energy sources. To meet the rising global demand, further advancement of the battery technology is imperative. One optimization pathway is to use battery materials that are more sustainable while also yielding improved electrochemical performance, contributing to both environmental and functional advancements. However, innovation must go beyond the material level, and new electrode design approaches for an efficient combination of high power and high energy systems are necessary.In this context, the three-dimensional (3D) battery concept with its increased exposed electrode surface, shows a great promise for enhanced electrochemical performance compared to the conventional flat designs of state-of-the-art electrodes. Targeting at the bottleneck of high power/high energy density systems, the incorporation of micro-structured channels within the electrodes improves lithium-ion diffusion pathways and minimize strain from volume expansion during electrochemical cycling.Our focus is the investigation of 3D electrode architectures generated by laser-processing techniques such as ultrafast laser ablation and laser-assisted printing. Working with ultrafast lasers offers the possibility to process materials while reducing thermal impact and allows the creation of well-designed and controllable electrode surface topographies. The adoption of this concept has already shown great impact in enhancing the high-rate capability and lifetime of conventional electrodes in lithium-ion batteries.[1-3] Expanding the scope, this work explores the applicability of laser-generated 3D electrode architectures to next-generation battery active materials such as high-voltage lithium nickel manganese oxide (LNMO) composites. On anode side, silicon/graphite and amorphous carbon is extensively investigated for lithium-ion batteries and sodium-ion batteries, respectively. To understand the impact of the manufacturing process, electrochemical evaluations are complemented by findings from laser-induced breakdown spectroscopy, SEM-EDX, Raman measurements, and Auger electron spectroscopy.In conclusion, this contribution highlights the promising advancements achieved by applying laser-generated 3D electrode architectures to next-generation battery materials and aims to provide valuable insights into this exciting frontier of battery research.[1] W. Pfleging, Nanophotonics 7 (2018) 549–573.[2] W. Pfleging, Int. J. Extrem. Manuf. 3 (2021) 012002.[3] M. Zaeh, Appl. Energy 303 (2021), 117693.

Electrodeposited Porous Ni-Fe-Co Thin Films By Hydrogen Templating Onto an Inverted Recessed Disk Electrode

Porous electrodes are advantageous for a variety of applications to enhance surface area per volume. Hydrogen templating is one well-known method to generate a porous metal, where metal deposits around generated gas bubbles from the same electrode surface. The technique has been demonstrated with noble (e.g., Au, Ag, Cu) and less noble (e.g., Ni) elemental deposits, but few alloy system.1 Ni-Fe-Co is of interest due to its electrocatalytic ability towards the oxygen evolution reaction for alkaline water splitting. Rafailović et al.2 galvanostatically electrodeposited an alloy at very high current density at pH 2 having 20 micron pore size with nano scale dendritic features, and Li and Podlaha3 potentiostatically electrodeposited Ni-Fe-Co alloys at pH < 0.5 into polycarbonate templates along with hydrogen templating to create pores in nanowires. There was a large distribution of pore size between 10 and 100 nm with the largest percentage between 20 and 40 nm. To better understand the control of pore size in the Ni-Fe-Co alloy system an inverted rotating disk electrode was used to control the limiting current of the proton reduction reaction during alloy electrodeposition. A boric acid, simple salt electrolyte was used with a three-electrode system to generate polarization curves and electrodeposits at different electrode rotation rates. The influence of mass transport and hydrogen bubble formation at different rotation rates were examined and affected porosity. Porosity was characterized by scanning electron microscopy (SEM) and the inspection of current during ferri/ferrocyanide polarization. Porous films were observed for deposits galvanostatically fabricated at current densities above the proton reduction limiting current density, but before water reduction, producing pore sizes on the order of 10s to 100s of nm, but below a micron. The ratio of the applied current density to proton reduction limiting current density was an important factor. J. Plowman, L. A. Jones, and S. K. Bhargava, Chemical Communications, 51, 4331-4346 (2015).D. Rafailović, C. Gammer, C. Rentenberger, T. Trišović, C. Kleber, and H. P. Karnthaler, Nano Energy, 2, 523-529 (2013).D. Li and E. J. Podlaha, Nano Letters, 19, 3569-3574 (2019).

(Invited) The Influence of Magnetic Fields on the Oxygen Evolution Reaction Catalyzed By Cobalt-Iron Oxide Nanowire Arrays

To mitigate climate change through the establishment of a renewable energy infrastructure, advancements in energy storage technologies are imperative. Electrochemical water splitting via electrolyzers enables the conversion of electrical energy into chemical energy. However, the performance of these devices, particularly that of the oxygen evolution reaction (OER) occurring at the anode, still needs to be improved. Previous studies have demonstrated that magnetic fields can induce convective flow to the electrode through Lorentz and Kelvin force effects, thereby improving the mass transport.[1] In contrast to the Lorentz force, the Kelvin force can be substantially increased by introducing magnetic nanostructures to create high magnetic field gradients in the vicinity of the electrode surface.[2] Given the magnetic properties inherent to many earth-abundant metal-based and nanostructured electrocatalysts promising for the OER, there is potential for intelligently designing electrodes to leverage magnetic field effects in the future. However, a comprehensive understanding of these magnetic field effects is currently lacking. In the scope of this work, we aimed to systematically investigate the influence of magnetic fields on the oxygen evolution reaction. Considering the substantial magnetic field gradients generated by magnetic nanowires, we fabricated arrays of freestanding cobalt-iron oxide nanowires to explore the influence of magnetic fields on the oxygen evolution reaction catalyzed by these nanostructured electrocatalysts. Templated electrodeposition of cobalt-iron alloy into the pores of anodic aluminum oxide membranes enabled a straightforward control over nanowire diameter and length. Subsequent removal of the aluminum oxide template in alkaline solution yielded cobalt-iron oxide nanowires composed to 60% of Fe and 40% of Co standing freely on an electrochemically stable gold substrate. Superimposing a magnetic field during water oxidation on the so-prepared nanowire arrays resulted in an increase in the measured oxidation current (see Figure). To deconvolute the contributions of the Lorentz and Kelvin force, experiments were conducted in two different magnetic field orientations: either parallel or perpendicular to the electrode surface. In the parallel orientation, a linear correlation between the increase in current and the strength of the applied magnetic field was observed. In contrast, when the magnetic field was aligned perpendicular to the electrode surface, a plateau in the current enhancement manifested at higher magnetic field strengths, indicating different dominant effects in the two configurations.[1] K. Ngamchuea, K. Tschulik, R. G. Compton, Magnetic control: Switchable ultrahigh magnetic gradients at Fe3O4 nanoparticles to enhance solution-phase mass transport, Nano Res. 2015, 8, 3293–3306.[2] L. M. Monzon, J. Coey, Magnetic fields in electrochemistry: The Kelvin force. A mini-review, Electrochem. commun. 2014, 42, 42–45. Figure 1

Understanding Electrode-Electrolyte Interfaces in Gel Polymer Electrolytes Using in-Operando Raman Spectroscopy

Gel polymer electrolytes hold enormous potential for advancing battery performance and technology, promising high energy densities and safe, rechargeable quasi solid-state batteries. GPEs offer higher ionic conductivities than solid electrolytes and enhanced safety in comparison to liquid electrolytes. A particular advantage of these electrolytes has been their ability to create robust electrode electrolyte interfaces that guide uniform deposition and stripping of lithium via their mechanical strength from the polymer and interface species that form during initial cycling.Herein we report that 1:1 dimethoxyethane (DME) and dioxolane (DOL) with lithium bistrifluoromethanosulfonyl imide (LiTFSI) and lithium nitrate entrapped in Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) gel polymer electrolytes have shown stability for up to 500 hours in lithium metal symmetric cells at 1 mAh/cm2 and performs at 5mAh/cm2 in dynamic symmetric cell cycling. To understand the fundamental interfacial phenomenon governing lithium deposition and growth in this system in-operando Raman was conducted on an anodeless Cu|PVDF-HFP|Li cell. Copper was sputtered onto the polymer electrolyte before assembly with a thickness of 20nm, providing an optically transparent electrode through which the Raman laser could pass through to detect interfacial species. We observe that PVDF-HFP acted as a chemically stable polymer electrolyte while Raman shifts associated with TFSI anions disappear near the electrode surface. The spectral and electrochemical data allow us to build a model for the growth and evolution of interfaces in an anodeless lithium metal battery cell with a GPE.Acknowledgement: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DE‐SC0014664. Figure 1

Investigating Cathode Dynamics in Realistic Desalination Reactors Using Operando High-Energy Synchrotron X-Ray Microscopy

Four billion people suffer from lack of clean water at least one month of the year.[1] This critical water shortage applies not only to the supply of potable water, but also to water for use in industrial, agricultural, and energy applications. While water resources like seawater are abundant, hardly any water resource is clean enough for direct use. Desalination provides a methodology to render unusable waters from such water resources fit for use. An innovative and particularly energy-efficient electrochemistry-based approach is the Desalination Battery (DB), which stores the energy input during desalination in chemical bonds between ions and faradaic electrode, allowing for its recovery during the salination process. DBs are at the forefront of the water-energy nexus[2]. While they are promising for seawater desalination (e.g., for seawater to brackish water conversion), practical implementation and their full potential still need to be unlocked. To this end, foundational understanding of the atomic- to electrode-scale physics/chemistry underlying functionality and degradation must be unraveled.Towards this end, we utilized our unique flow-by reactor setup to combine electrochemistry, conductivity, and temperature measurements with high-energy (75 keV) operando synchrotron X-ray diffraction (HEXRD) microscopy. Our investigation encompasses both the atomic and electrode levels, using a 3-electrodes setup with LiMn2O4 and Na0.44MnO2 as electrode active materials. As such, we were able to simulate a realistic electrode environment for operando measurements, as well as observe spatially resolved structural changes by scanning the beam across the electrodes surface. These phenomena are manifested through changes in unit cell parameters and the emergence of new phases during desalination cycles. Specifically, we tracked the changes in XRD patterns over the course of several desalination cycles in LiCl and NaCl solutions, as well as synthetic seawater and mixed solutions of LiCl/MgCl2. We were able to observe high selectivity of LiMn2O4 towards Li+, even in the highly concentrated synthetic seawater solutions, and could not observe the emergence of a new Mg+ rich phase down to potentials of 0 V vs. AgCl. Na0.44MnO2 exhibited good cycling behavior in synthetic seawater akin to pure NaCl solutions, and apart from the Na+ rich phase showed no signs of additional new phases, suggesting a highly selective nature towards Na+. Furthermore, we compared constant current and constant potential protocols and observed distinct differences in peak shift behavior. Ongoing analysis of the unit cell parameters and atomic positions allows us to allocate specific intercalation sites to specific potentials, providing foundational insight into the chemistry and physics underlying the selectivity of these materials.Literature:[1] M. M. Mekonnen, et al., Sci Adv 2016, 2, e1500323.[2] Q. Li, et al., Adv Sci (Weinh) 2020, 7, 2002213.

Electrochemical and Spectroscopic Investigations of Bismuth(III) Pharmaceuticals with L-Glutathione

Due to the importance of L-cysteine in the human system, the interaction of metals with this amino acid are worthy of investigation by various methods. In this laboratory1, we have investigated the interaction of bismuth(III) compounds with L-cysteine by both cyclic voltammetry and UV-VIS spectroscopy in an attempt to understand the role of bismuth in treating gastrointestinal maladies.2 The addition of bismuth(III) compounds to solutions of L-cysteine causes a negative potential shift for bismuth(III) reduction as an indication of complex formation between bismuth(III) and L-cysteine. This interaction is also evident by the appearance of a UV-VIS spectroscopic band at 340 nm (Bi-sulfur bond). Even at low pH values (pH 1.0), electrochemical studies show evidence of some kind of interaction even when there is no 340 nm band. These investigations have been conducted at pH 1.00 and 3.00 to simulate conditions in the human stomach and at pH 7.40 MOPS [(3-N-morpholino)propanesulfonic acid] to simulate general physiological conditions, in particular the intestinal tract. Recent work has involved extension of this work to L-glutathione, a tripeptide incorporating L-cysteine, under similar conditions. As might be expected, these interactions are considerably more complicated than those involving L-cysteine. As an example, there is a considerable positive potential shift for the reduction of bismuth(III) citrate in the presence of L-glutathione on the first and second voltammetric sweeps at gold and glassy carbon electrodes. This behavior evidently reflects the rather long (several seconds) time required for the re-formation of the bismuth complex with L-glutathione after its reductive ligand (L-glutathione) loss during bismuth(III) reduction on the first sweep. In addition, there is evidence of a film buildup on the electrode surface as observed by peak current increases during multiple potential sweeps. These observations are planned for inclusion in this symposium presentation.References T. Cheek and D. Peña, J. Electrochem. Soc., 167, 155522 (2020)Li, R. Wang, and H. Sun, Acc. Chem. Res., 52, 216 (2019).

Operando Tracking the Dissolution and Deposition Dynamics in Aqueous Zn-MnO2 Batteries

Aqueous Zn–MnO2 batteries have received extensive attention for next-generation large-scale energy storage because of their low cost and outstanding safety. Despite efforts to achieve better performances, the charge-storage chemistry of MnO2 cathodes remains controversial. Zn-ion insertion, Zn-ion/proton co-insertion, proton insertion, and electro-dissolution have been proposed as the mechanism of the MnO2 cathodes. More specifically, the pathway of Mn dissolution is debatable: while intercalation chemistry leads to dissolution caused by the Jahn–Teller effect of Mn(III), electro-dissolution relies on a conversion from Mn(IV) to Mn(II). Furthermore, it is recently considered that Mn dissolution/redeposition efficiency is crucial to the reversibility of MnO2 cathodes, depending on pre-added Mn in the electrolyte. The role of trace Mn additive is also confusing. Last but not least, Mn dissolution and deposition is conjectured to be linked to the dissolution/redeposition of Zn‐based species-that is, Zn4SO4·(OH)6·xH2O (ZSH). To understand these key scientific questions that enlighten the further design of materials and electrolytes, it is imperative to develop operando measurements of the MnO2 cathodes. In our study, we utilized synchrotron X-ray fluorescence microscopy with high spatial resolution to probe the evolution of Zn and Mn species during electrochemical cycling. We can quantify the relationship between Zn and Mn concentrations from the electrode level to the single-particle level. We conclude that during the first discharge, MnO2 delivers the capacity by electro-dissolution, accompanied by the rapid precipitation of ZSH due to change of pH. ZSH surrounds the MnO2, which has high reversibility with the pre-added Mn additive in electrolytes. Our work provides in-depth insights into the complex Zn/Mn deposition and deposition near the electrode surface which will guide the further development of aqueous Zn-MnO2 batteries.

All-Diamond Boron-Doped Microelectrodes for Neurochemical Sensing with Fast-Scan Cyclic Voltammetry.

Neurochemical sensing with implantable devices has gained remarkable attention over the last few decades. A promising area of this research is the progress of novel electrodes as electrochemical tools for neurotransmitter detection in the brain. The boron-doped diamond (BDD) electrode is one such candidate that previously has been reported for its excellent electrochemical properties, including a wide working potential, superior chemical inertness and mechanical stability, good biocompatibility and resistance to fouling. Meanwhile, limited research has been conducted on the BDD as a microelectrode for neurochemical detection. Our team has developed a freestanding, all diamond microelectrode consisting of a boron-doped polycrystalline diamond core, encapsulated in an insulating polycrystalline diamond shell, with a cleaved planar tip for electrochemical sensing. This all-diamond electrode is advantageous due to its - (1) batch fabrication using wafer technology that eliminates traditional hand fabrication errors and inconsistencies, (2) absence of metal-based wires, or foundations, to improve biocompatibility and flexibility, and (3) sp 3 carbon surface with resistance to biofouling, i.e. adsorption of proteins or unwanted molecules at the electrode surface in a biological environment that impedes overall electrode performance. Here, we provide findings on further in vitro testing and development of the freestanding boron-doped diamond microelectrode (BDDME) for neurotransmitter detection using fast scan cyclic voltammetry (FSCV). In this report, we elaborate on - 1) an updated fabrication scheme and work flow to generate all diamond BDDMEs, 2) slow scan cyclic voltammetry measurements of reference and target analytes to understand basic electrochemical behavior of the electrode, and 3) FSCV characterization of common neurotransmitters, and overall favorability of serotonin (5-HT) detection. The BDDME showed a 2-fold increased FSCV response for 5-HT in comparison to dopamine (DA), with a limit of detection of 0.16 µM for 5-HT and 0.26 µM for DA. These results are intended to expand on the development of the next generation BDDME and guide future in vivo experiments, adding to the growing body of literature on implantable devices for neurochemical sensing.

Electrochemical Detection of Neutrophil Gelatinase-Associated Lipocalin (NGAL) in Simulated Urine Using Au@Si/Ni-Porphyrin Nanocomposite for the Prediction of Kidney Injury

Kidney Injury is multifactorial out of which ureteropelvic junction obstruction is one of the major causes of concern. There are a multitude of methods for monitoring the deterioration of renal function like serum creatinine levels, ultrasound scans, renograms, and nuclear scans like radiolabelled MAG3 and DMSA which require repeat evaluation or sedation during the process. Many of the biomarkers utilized for the assessment of kidney injury are expressed at the later stages. Urine NGAL is a promising biomarker for risk stratification which is reported to be expressed at the onset of ureteropelvic junction obstruction (UPJO) and is a gold standard for the estimation of tubular injury. Urinary NGAL is also reported to be a specific marker for the prediction of hydronephrosis in children who require surgical intervention. The kidney injury cut-off for NGAL in urine is 185ng/mL and 48 ng/mL in the adult and pediatric population groups respectively. Electrochemical detection of NGAL in patient urine is a fast, reliable, non-invasive, accurate, and cost-effective method for monitoring kidney health to segregate patient groups that require surgical intervention.In this study, an electrochemical sensor was designed with Au(150nm) electrodes fabricated using thermal evaporation on a flexible substrate (PET; 250μm) by using Cr(20nm) as the seed layer. The electrode was immobilized with Au@Si core-shell decorated on Ni-porphyrin nanosheets functionalized with anti-NGAL using covalent chemistry. The nanocomposite was synthesized through a bottom-up approach where the Ni-tetrakis(4-carboxyphenyl) porphyrin nanosheets were synthesized using the solvothermal method in an organic phase (DMF) followed by purification and suspension in ethanol medium. The Si nanocrystals were synthesized in a citrate medium with APTMS as the precursor followed by purification via dialysis. The purified Si nanocrystals (60ppm) and Ni-porphyrin nanosheets (880ppm) were treated in chloroauric acid (0.25mM) and the reducing agent trisodium citrate (34mM) to form Au shell. The physicochemical and electronic properties of the synthesized nanocomposite were evaluated through XRD, XPS, microscopic analysis(TEM, SEM), AFM, UV-Vis, FTIR, and Raman spectroscopy. The resultant nanocomposite was purified and linked to anti-NGAL (100μg/mL) through EDC (0.4M)/NHS (0.1M) chemistry. The antibody-nanocomposite was immobilized on the fabricated Au electrodes (working electrode surface area: 0.35mm2) through BSA(1.2mM)/glutaraldehyde (2.5% v/v) crosslinking. The quantitative electrochemical estimation of NGAL antigen spiked in 0.1M PBS (pH=7.2±0.2) and simulated urine was performed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The shelf life of the fabricated sensors was evaluated for 30 days (stored at 4˚ C until use) over the concentration range of 0-5000 ng/mL. The amount of test solution required per measurement for the miniaturized electrodes was 6μL.The sensing mechanism of the electrochemical platform was established through CV by varying the scan rate (0.05 V/s - 2.5 V/s) for 500ng/mL in 0.1M PBS and urine. With increasing scan rate a linear relationship between log ip and log ν was observed. For 0.1M PBS, the process was largely capacitive at various detected potentials (b=0.94 @ 0.5V; b=0.86 @ 0.3V; b=0.85 @ 0.07V). However, in the case of simulated urine, the electrochemical process was diffusion-limited at 0.6V (b=0.49). Therefore, to obtain higher current sensitivity in the diffusion-limited regime, DPV was adopted. With increasing concentration of antigen NGAL, a monotonic decrease in the redox current at 0.6V and 0.45V potential was observed. This signifies that the presence of NGAL antigen leads to the formation of antigen-antibody complex immobilized on the surface of the nanocomposite translating into an increase in the resistance at the electrode surface leading to a decrease in the redox current. The decrease in the current was proportional to the increase in the amount of the test antigen. The sensitivity of the sensor at 0.45V and 0.6V was 2.22 nA/ng mL-1/mm2 and 0.51 nA/ng mL-1/mm2 respectively with the lowest limit of NGAL detection as 12.5ng/mL in simulated urine by using DPV. Similarly, for CV the sensitivity of the sensor at 0.56V was 3.48 nA/ng mL-1/mm2 with 22ng/mL as the limit of detection. The sensor performance was evaluated without the use of nanocomposite (only antibody) as a control for comparison.Therefore, this study is a proof of concept for an effective electrochemical sensor platform design for urinary NGAL detection using a novel nanocomposite. It was established that the use of nanocomposite provides a better surface area to volume ratio through the core-shell nanostructures decorated on the nanosheets translating into higher electrochemical activity. The sensing platform was found to be specific, sensitive, and stable making it a perfect candidate for a point-of-care-testing(POCT) platform. Figure 1

Controlling Current Distribution in Slurry Electrolytes for Redox Flow Batteries

Slurry electrodes have the potential to decouple the power and storage capacities of hybrid redox flow batteries1 (RFB). In more commonly studied true RFB chemistries, such as all-vanadium, the power and storage capacities can be considered separately2; the power capacity is dependent on the flow cell design while the storage capacity is dependent on the amount of positive and negative electrolyte that can be stored. These decoupled capacities allow true RFB’s to be highly scalable. However, in hybrid RFB chemistries, such as all-iron, solid metal is deposited within the flow cell during charge, limiting the storage capacity of the battery based on the geometry of the flow cell3. This limitation can be addressed by incorporating a slurry electrode in the negative electrolyte. By depositing the reduced metal on this mobile dispersion of electrically conductive carbon particles, hybrid redox RFB’s may achieve high scalability while utilizing less expensive materials, such as iron or zinc1,4. To successfully augment the scalability of hybrid RFB’s, the current distribution of the metal deposition reaction must occur predominantly on the mobile slurry electrode, rather than on the stationary current collector. This current distribution is dependent on numerous factors, including the electrical conductivity of the slurry electrode, the ionic conductivity of the electrolyte, the kinetics of the faradaic reaction, and mass transfer to both the stationary current collector and to the slurry particles. In this work, we explore three approaches to controlling the current distribution in slurry electrodes. In the first approach, we explore the utility of slurry electrodes consisting of multiple types of carbon particles. Our earlier work has shown that slurries of varying carbon type can have significantly different electrochemical performance5. Slurries consisting of carbon black particles with high specific surface area can minimize the kinetic resistance of the faradaic reactions but struggle to distribute current away from the current collector due to their low electrical conductivity. Meanwhile, slurries consisting of more electrically conductive, but lower surface area graphitic particles can facilitate faradaic current away from the current collector but may not minimize kinetic resistance to the same degree. By using a slurry electrode consisting of mostly graphitic particles with a small portion of high surface area carbon black, the faradaic current may be kinetically facile in addition to well distributed through the slurry. In the second approach, we explore options to hinder the ionic conductivity of the electrolyte. The faradaic current distribution through the slurry electrode depends heavily on the competition between the ionically and electronically conductive routes. Typically, the ionic conductivity is heavily favored due to the desire for high per-volume energy density and the low pH required to keep the metallic reactants soluble. By hindering the ionic conductivity of the electrolyte, either by utilizing viscosity increasing additives or by lessening the ionic concentration, the faradaic current may be better spread through the slurry. In the third approach, we explore options for controlling the current distribution via varying reaction kinetics on various electrode surfaces. While considerable work6,7 has been done comparing the reaction kinetics of homogeneous redox reactions on various electrode materials (glassy carbon, basal/edge plane graphite, platinum...) relatively little work has been done regarding metal deposition reactions. By changing the current collector material to one with poor deposition kinetics relative to the slurry electrode material, the current distribution may be enhanced on the slurry.(1) Petek, T. J. Enhancing the Capacity of All-Iron Flow Batteries: Understanding Crossover and Slurry Electrodes. Ph.D. Thesis 2015, No. May.(2) Weber, A. Z.; Mench, M. M.; Meyers, J. P.; Ross, P. N.; Jeffrey, T.; Liu, Q. Redox Flow Batteries, a Review. J. Appl. Electrochem. 2011, 41 (10), 1–72. https://doi.org/https://doi.org/10.1007/s10800-011-0348-2.(3) Dinesh, A.; Olivera, S.; Venkatesh, K.; Santosh, M. S.; Priya, M. G.; Inamuddin; Asiri, A. M.; Muralidhara, H. B. Iron-Based Flow Batteries to Store Renewable Energies. Environ. Chem. Lett. 2018, 16 (3), 683–694. https://doi.org/10.1007/s10311-018-0709-8.(4) Petek, T. J.; Hoyt, N. C.; Savinell, R. F.; Wainright, J. S. Slurry Electrodes for Iron Plating in an All-Iron Flow Battery. J. Power Sources 2015, 294, 620–626. https://doi.org/10.1016/j.jpowsour.2015.06.050.(5) Tam, V.; Wainright, J. Electrochemical Behavior of Low Loading Slurry Electrodes for Redox Flow Batteries. J. Electrochem. Soc. 2023, 170 (1), 010538. https://doi.org/10.1149/1945-7111/acb10a.(6) Mccreery, R. L.; Mcdermott, M. T. Comment on Electrochemical Kinetics at Ordered Graphite Electrodes. Anal. Chem 2012, 84. https://doi.org/10.1021/ac2031578.(7) Chen, P.; McCreery, R. L. Control of Electron Transfer Kinetics at Glassy Carbon Electrodes by Specific Surface Modification. Anal. Chem. 1996, 68 (22), 3958–3965. https://doi.org/10.1021/ac960492r. Figure 1

High Entropy Alloys as Bifunctional Catalysts for Reversable Metal Air Batteries

The development of stable non-noble metal bifunctional catalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are essential for technologies such as reversible metal air batteries. We have shown that synthesis of high entropy alloy nanoparticles formed through a novel synthesis method where metal precursor containing aqueous nanodroplets freely diffusing in an emulsion solution, collide with an electrode surface and the metal precursors are reduced, thus forming a homogeneous particle containing the predetermined metal composition. Afterwards, the particles are annealed at a low temperature causing a phase separation of the metals, forming a metal nanoparticle that is surrounded by a stabilizing metal oxide. We have demonstrated that equimolar Fe, Ni, Co, Cr, and Mn solutions produce bifunctional FeNiCo metal nanoparticles surrounded by CrMnOx that are very active for both OER and ORR. The synthesis technique also affords the flexibility to tailor composition of the nanoparticles and potentially provide access to previously difficult to synthesize compositions and may alter the electrocatalytic reaction pathways and activities.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525

Layered Double Hydroxides As a Method for Decorating Electrodes with Metal Particles for Sensing the Antibiotic Ornidazole

The use of metallic particles and nanoparticles to improve the detection capabilities of sensors has been widely reported in literature and thus, a method of decorating electrodes reliably and easily with metallic particles is of great interest. In this regard, Layered Double Hydroxides (LDHs) are of particular interest to act as a source of metal particles. LDHs are inorganic two-dimensional compounds with the general formula [M1-x 2+M3+ x(OH)2]x+(An-)x/n.mH2O where M is two different metals and A is the intercalated anion between the stacked layers of divalent and trivalent M2+/M3+ ions to produce a 2 nanosheet structure [1]. In this study LDHs are synthesised hydrothermally, which involves placing metallic salts of the desired metals into an aqueous solution in a sealed autoclave and heating to a high temperature to produce a high vapour pressure environment. From this method various elements can be combined to produce bimetallic and trimetallic LDHs.The obtained LDH powder is then dispersed in ethanol and water using ultrasonication and layered onto the electrode surface by means of drop-casting. It can then be easily reduced using cyclic voltammetry to act as an efficient method of decorating an electrode with metallic particles of the desired elements. In this study, a variety of layered double hydroxides were synthesised using combinations of different elements and then subsequently used to reduce metal particles onto a glassy carbon electrode.A variety of bimetallic and trimetallic LDH compounds containing copper, iron, cobalt, and nickel were investigated. To compare the sensing capabilities of these reduced metal particles, the reduction of the antibiotic ornidazole was used as an analyte. Ornidazole is a member of the nitroimidazole antibiotic family that is heavily employed in the treatment of both human and animal infections [2]. This widespread use has led to the accumulation of the antibiotic in aquatic environments, posing a serious health risk due to its toxicity and the risk of antimicrobial resistance [3]. Thus, a sensor capable of quickly and reliably detecting the antibiotic is of great importance. To enhance the conductivity of the modified sensors, a drop-casted layer of functionalised carbon black was combined with the metallic particles.For the detection of ornidazole, the copper-iron (CuFe) particles were concluded to be optimum, displaying a detection range of 0.2 uM to 600 uM. Characterisation studies were performed on the CuFe particles using SEM, XRD, XPS, FTIR, and EDX. Investigations were carried out into the behaviour of the sensor at varying pH values and to determine the reaction kinetics of detection. To study the selectivity of the sensor interferants were introduced to the antibiotic solution and experiments were performed in real water samples gathered from various locations.[1] A., Karmakar, K., Kannimuthu, S., Sam Sankar, K., Sangeetha, R., Madhu, & S., Kundu. Journal of Materials Chemistry A. 2020[2] Q. Wang, C. Wang, Q. Wang, & Z. Wang, Journal of Agricultural and Food Chemistry., 2019, 67(41), 11527-11535[3] W. El, N. Tajat, A. Idelahcen, M. Tamimi, S. Qourzal, A. Assabbane, & I. Bakas, Microchemical Journal, 2023, 195, 109397

Electrochemical Biosensor Enabling Sensitive Detection of miRNA Biomarkers

Biomarkers are becoming increasingly important for early diagnosis, exploration of responses to medication, and assessment of therapeutic efficacy of various diseases [1]. Increasing evidence shows that miRNAs can be employed as biomarkers for cancer and cardiovascular diseases. In this context, the development of powerful electrochemical diagnostic tools has grown in interest due to their sensitivity, speed, and low cost [1]. Additionally, electrochemical technologies offer a facile means to fabricate well-defined nanostructured surfaces in a controlled environment. The gold (Au)-based surface stands out for its ability to improve charge transfer characteristics, enhancing conductivity. It also serves as a stable substrate for further modification, enabling the detection of target analytes [2]. Here, we utilized an electrochemical platform by using a 3-electrode carbon-based screen-printed electrode (SPE) electrochemically modified with gold and subsequently attached a specific DNA-based redox probe to detect low levels of miRNAs as a biomarker. Our design was applied to detect miRNA-1 (5′-TGG AAT GTA AAG AAG TAT GTA T-3′), demonstrating exceptional sensitivity and a low detection limit (LOD) of 120 fM. We also discuss how the developed platform broadly benefits numerous other miRNA sequences. Device preparation method: A screen-printed electrode (SPE) consisting of a 3 mm diameter carbon working electrode, an Ag reference electrode, and a carbon counter electrode was used as a base for device development. The bare SPE was activated during 10 cycles of cyclic voltammetry (CV) with potentials ranging from -0.5 to +1 V at a scan rate of 20 mVs-1 using PBS as the electrolyte. Before gold electrodeposition, the activated SPE was rinsed with PBS and deionized water. The electrode was submerged in a solution of 115 mM HAuCl4 (in 0.5 M H2SO4) during 10 CV cycles with the same parameters described above. Next, the DNA-probe sequence was attached to the working surface of the Au-decorated screen-printed electrode (Au-SPE). The DNA-probe sequence was modified in advance with C6-S-S-R at the 5′ end (enabling covalent binding onto Au) and methylene blue (MB) at the 3′ end (allowing electron transport at the electrode). Before modification of SPE, the disulfide bond was reduced using tris(2-carboxyethyl)-phosphine hydrochloride) (TCEP) to enable covalently attachment of the HS-DNA-MB probe to the Au-SPE [2]. The attachment of the DNA-probe sequence was achieved by placing 10 µL of the diluted probe onto the working electrode area and allowing for 1 hour of modification at room temperature to take place, as shown in Fig. 1(A). Results & Discussion: The device was evaluated for analytical performance in the presence of increasing target concentrations, as shown in Fig. 1 (A). In the absence of a miRNA-1 target, the stem-loop structure of the DNA probe remains closed, forcing the redox MB-reporter into proximity to the electrode, allowing for efficient electron transport. In the presence of miRNA-1, the target molecule binds to a complementary sequence of the DNA probe, opening the loop. The structure assumes a relatively rigid conformation where MB is farther from the gold surface, reducing the observed signal, Fig. 1 (B). The observed current gradually decreases upon the successive addition of miRNA target molecules for both cathodic, Ipc, and anodic, Iac, peaks. Using the dependence of anodic peak, Iac, the sensor was calibrated as a function of added miRNA-1 concentration in the range between 0 and 4 nM. Using the calibration curve shown in Fig. 1 (C), the detection limit was estimated to be 120 femtoM. The device was further tested for stability and exhibited robust performance over an extended period displaying minimal fluctuations in the recorded current. While we demonstrate the sensitive detection of miRNA-1, the design can be easily adapted for other miRNA sequences [3]. Additionally, it introduces exciting prospects for multiplexing, where multiple miRNA sequences can be easily detected with only minor adjustments to the established design. Fig. 1 (A) Schematics of the device fabrication process and mechanism for the development of Smart Electrochemical Sensors setup; (B) Cyclic Voltammetry (CV) responses during Au electrodeposition (black) in the absence of miRNA-1 target (red) and presence of miRNA-1 target (blue); (C) The device response curve concerning successive addition of miRNA-1 target molecule into the device chamber (different concentrations of target from 0 to ~ 4000 pM), the inset shows CV response used to plot the calibration curve. Acknowledgment: NSF DMR 2204027, US DOE EPSCoR DE-SC0024284

Next-Generation Electrochemical Biosensing Based on Ternary Nanocomposites of nMoS2@Rgo@MWCNT for Label-Free Cancer Biomarker Detection in Undiluted Human Serum

Sperm protein-17 (Sp17) is a cancer-testicular antigen that is expressed in various types of cancers and has been proposed as a potential biomarker for cancer. However, the detection of Sp17 in human serum is challenging due to its low concentration and the lack of specific and sensitive methods. Hence, there is an urgent need to develop fast, accurate, reliable, and cost-effective disposable biosensors for Sp17 detection. Herein, we report sensing of Sp17 with a disposable carbon cloth-based electrode (CC) modified with a ternary nanocomposite comprising molybdenum disulphide (MoS2), reduced graphene oxide (rGO), and multi-walled carbon nanotube (MWCNT). The nanocomposite was synthesized by a facile hydrothermal method and was well-characterized in terms of structural, morphological, and chemical attributes using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy spectral techniques, and electrochemical studies to prove the robust formation of the electroactive ternary nanocomposite and its suitability for Sp17 detection. The nanocomposite exhibited excellent electrocatalytic activity, biocompatibility, and stability. We immobilized a Sp17-specific antibody on the surface of the nanocomposite-modified electrode and used it as a biosensor for Sp17 detection. The biosensor showed a linear response range from 0.01 to 11 ng mL-1 and a limit of detection (LOD) and limit of quantification (LOQ) of 0.23 ng mL-1 and 0.79 ng mL-1, respectively having sensitivity of 9.97 mA ng mL-1 cm-2. The biosensor was successfully applied to detect Sp17 in human serum samples and showed good accuracy, reproducibility, and selectivity, making it helpful for use in translational medicine research and clinical applications. The biosensor also demonstrated a high correlation with a commercial enzyme-linked immunosorbent assay (ELISA) kit. Our results suggest that the proposed biosensor is a promising tool for Sp17 detection in human serum and could be useful for the diagnosis and prognosis of ovarian cancer and other Sp17-related cancers. Keywords: Carbon cloth; Biosensor; Electrochemistry; Sperm protein 17; Cancer biomarker; Nanocomposite

Synchrotron Infrared Nano-Spectroscopy and Imaging of Lithium Fluoride in the Solid Electrolyte Interphase on Li-Ion Anodes

The solid electrolyte interphase layer that forms on the surface of the negative electrode in Li-ion batteries is crucial for battery cycle/calendar life, rate performance and safety. This 10's of nanometers layer is formed from the decomposition of the liquid electrolyte and its passivation properties are very sensitive to its formation and aging conditions. Despite this critical role, there is still a lack of fundamental understanding of how its structure and composition relate to its stability and passivation performance.Amongst the SEI products that form during the decomposition of liquid electrolyte, lithium fluoride (LiF) is a ubiquitous component and many attribute its presence to be a determining factor of a well passivated interface. Despite the importance, LiF’s nanostructure and distribution within the SEI layer is rarely investigated due to the lack of suitable characterization techniques. X-ray photoelectron spectroscopy (XPS) is the main tool to identify LiF in the SEI layer, but its micron scale lateral resolution precludes any nanometer scale mapping of LiF’s distribution which limits its ability to identify the role LiF plays in the SEI layer.Recently our group has been characterizing the SEI layer of Li-ion negative electrodes with nano-Fourier transform infrared spectroscopy (nano-FTIR).1,2 Nano-FTIR is a scanning probe technique based in a typical atomic force microscope (AFM) in which a broadband laser illuminates a metallic tip/sample interface. The metallic tip acts as an antenna, focusing the infrared light adjacent to the interface and creating a near-field interaction. By operating in constant tapping mode and due to the nonlinearity of the near-field signal on the tip/sample distance, the corresponding backscattered light from the near-field interaction with the sample can be separated from the background with lock-in amplification. The result is IR reflection and absorption spectra with lateral resolution close to the tip radius (ca. 20 nm). This far exceeds the diffraction limited resolution of typical IR microscopy (~10’s µm) creating new opportunities for IR characterization on nanometer length scales.In this talk, we’ll discuss our recent work related to utilizing synchrotron-based nano-FTIR to characterize and image LiF in the SEI layer of Li-ion based negative electrodes. The synchrotron infrared light source allows the detection of photons out to the far-IR (322 cm-1 limit) which enables the detection of the vibrational modes of Li containing inorganic phases such as LiF, Li2O, and LiH. By comparing model thin film LiF nano-FTIR spectra with experimental spectra take from the surfaces of Cu, Si thin film, and a novel metallic glass anode, we can gauge the heterogeneity of the LiF in the SEI layer and then suggest different LiF formation mechanisms. Based on the results, we believe that nano-FTIR with a synchrotron based light source will be a key tool to unravelling the nanoscale structure of the SEI layer due to its nanoscale chemical sensitivity and nondestructive nature.This research was supported by the US Department of Energy (DOE)’s Vehicle Technologies Office under the Silicon Consortium Project directed by Brian Cunningham and managed by Anthony Burrell. This research used resources of the Advanced Light Source from beamline 2.4, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. References (1) Dopilka, A.; Gu, Y.; Larson, J. M.; Zorba, V.; Kostecki, R. Nano-FTIR Spectroscopy of the Solid Electrolyte Interphase Layer on a Thin-Film Silicon Li-Ion Anode. ACS Appl. Mater. Interfaces 2023, 15 (5), 6755–6767.(2) He, X.; Larson, J. M.; Bechtel, H. A.; Kostecki, R. In Situ Infrared Nanospectroscopy of the Local Processes at the Li/Polymer Electrolyte Interface. Nature Communications 2022, 13 (1), 1398.

Unsuspected Organometallic Fibers Used As Potential Separators for Supercapacitors Device

Since the last decade, the interest of organic frameworks for electrochemical application the been more studied.1 In general, very few works have been found in the literature. We can mainly mention the use of these derivatives in the presence of inorganic materials both to form solid electrolytes or to protect electrodes. For example, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (H4DOTA) has been used to functionalize PVA to coat the surface of the negative electrode in order to suppress its degradation.2 This resulted in the improvement of the electrochemical properties of the LMNO/graphite cell. Recently, Kim et al. reported the addition of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane to a carbonate-based electrolyte intended to stabilize the Li metal-electrolyte interface by improving the solid electrolyte interphase.3 More recently, Liu et al. reported a novel carbonyl network polymer NP4 used as a cathode material for organic lithium batteries.4 Very few examples of fully organic frameworks used as separators have been reported.Therefore, our investigation to develop new supramolecular metal-based objects via a self-assembly process of molecular bricks will be presented. The work on cyclen derivatives allows to obtain metal complexes very stable able to pack in a well oriented dimension. Cyclen derivatives, in the presence of metal salts such as copper or zinc chlorides and polar solvents such as aliphatic alcohols, have a strong affinity for metals and spontaneously assemble in some conditions.5 In terms of applications, these self-assembled "organometallic" fibers represent an original and relatively easy to access substrate for fabricating 1D organic objects. Moreover, taking advantage of the properties and potentialities of these materials, we format an adequate shape to handle it as a potential separator for application in Energy Storage Systems (ESS).After a presentation of their synthesis and their formatting as potential separators for supercapacitors, preliminary electrochemical studies will be discussed. 1. J. Mater.Chem. A 2016, 4, 16812; ACS Energy let., 2022, 7, 885.2. ACS Appl. Energy Mater., 2021, 4, 128.3. ACS Appl. Matter. Interface, 2022, 14, 35645.4. J. Electoanalytical. Chem. 2023, 117251.5. Chem. Commun. 2010, 46, 1464. Figure 1

Electrochemical Amalgamation Optimization as Part of the Development of the OREATE Process

Oxide reduction by electrochemical amalgamation and thermal extraction (OREATE) is an electrochemical process in which metal oxides are converted to highly pure metals. This process that is currently being developed at LANL involves the dissolution and chlorination of the metal oxide into an acidic medium. This metal cation is then electrochemically amalgamated via reduction using a mercury pool cathode. Finally, mercury's high vapor pressure allows an easy thermal extraction process to obtain the metal. In addition to its ability to electrochemically form amalgams, mercury is used because it has a high hydrogen evolution overpotential, allowing for a higher current efficiency for reduction of the metals in acidic solution. As a critical step of the OREATE process, the electrochemical amalgamation reaction must be optimized in order to advance the overall performance.In this work, we studied the electrochemical amalgamation of cerium through anodic stripping voltammetry (ASV) experiments using a silver-based mercury film electrode (SBMFE). The SBMFE allows for the electrochemical amalgamation to be optimized at a smaller scale than the mercury pool, which not only minimizes the amount of mercury needed, but also drastically reduces the experiment time. This study included several different experimental parameters such as the pH of the buffered solution, concentration of cerium, reduction potential, and temperature. For each parameter, the reaction rate and current efficiency were evaluated to determine the optimal conditions for the electrochemical amalgamation reaction.The results showed that the pH of the buffered solution must be 3.5 or lower to avoid the formation of cerium hydroxides, which can passivate the surface of the mercury electrode. However, an increasingly acidic solution promotes the hydrogen evolution reaction, which directly competes with the electrochemical reduction of cerium, decreasing the overall current efficiency. Likewise, it has been demonstrated that an increase of the cerium concentration in solution drops the current efficiency of the electrochemical amalgamation reaction. This effect can be explained by the fact that cerium is a small cation with a +3 charge that leads to a high degree of solvation. Therefore, as the cerium concentration in solution increases, more water molecules are brought to the electrode surface during electrochemical amalgamation. This favors the water reduction reaction that increases hydrogen evolution and lowers current efficiency. However, increasing the concentration of cerium enhances the reaction rate of the electrochemical amalgamation, resulting in more cerium entering the mercury film. Furthermore, as the reduction potential is moved towards more negative potentials, the reaction rate increases. However, a more negative reduction potential promotes a faster hydrogen evolution reaction, which diminishes the current efficiency. Finally, it has been demonstrated that temperature increases the reaction rate, though it does not have a significant effect on the current efficiency.In conclusion, a variety of system parameters were explored for their effect on current efficiency and reaction rate of the electrochemical amalgamation reaction. This allowed for the determination of the optimal parameters to be used during the electrochemical amalgamation in the large-scale OREATE process.