bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Electrochemical CO2 Reduction Using DNA-Based Nanomaterials
Authors: Fan Gang , Furst Ariel L
Published: September 2023

Carbon dioxide can be converted to high value chemical products. Small molecules have been demonstrated to catalyze electrochemical CO2 reduction (ECR) process. To apply them in a controlled manner, these catalysts are required to be proximal to an electrode surface for the reaction to proceed. We developed a general method to readily place molecular catalysts on electrodes using DNA hybridization-based immobilization. DNA-catalyst complexes were synthesized through an optimized conjugation method and immobilized on screen-printed carbon electrodes and carbon paper electrodes using DNA hybridization. We found that this immobilization method improved the catalytic efficiency of molecular ECR catalysts for both an iron and a cobalt porphyrin-based catalyst. Importantly, DNA-modified catalysts demonstrated higher stability than their unmodified counterparts. Using this method, we could specifically control the distance between the catalytic sites to assemble DNA-catalyst nanostructures and elucidate the structure and function relationship of CO2 electroreduction process. This method affords tunability and specificity, providing a new strategy to improve electrochemical CO2 reduction efficiency.
Alternating Current Voltammetry (ACV) for Quantifying Electrochemical Dimerization of NAD+ Biomimetics
Authors: Hickey David P. , Bruggeman Chase
Published: September 2023

Biomimetics of nicotinamide adenine dinucleotide (mNADH) are promising cost-effective alternatives to their natural counterpart for biosynthetic applications; however, attempts to recycle mNADH often rely on coenzymes or precious metal catalysts. Direct electrolysis is an attractive approach for recycling mNADH, but electrochemical reduction of the oxidized mimetic (mNAD+) primarily results in the formation of an enzymatically inactive dimer. A primary focus of our research is to design synthetic analogues of NAD+ and NADH that are both enzymatically active and electrochemically regenerable. We will present our recent progress utilizing alternating current voltammetry (ACV) to quantify the electrochemical dimerization of structural derivatives to NAD+, which can exceed second order rate constants of k > 107 M-1 s-1. We utilize this data to elucidate structure-reactivity relationships that lead to dimerization over the preferred formation of 1,4-dihydronicotinamide in NAD+ and its biomimetics, and we will describe strategies to prevent dimerization of electrochemically reduced NAD+.
Unraveling Spatial Charge Density Distributions at Electrode-Electrolyte Interfaces
Authors: Bonagiri Lalith Krishna Samanth , Panse Kaustubh S. , Zhou Shan , Wu Haiyi , Aluru Narayana R. , Zhang Yingjie
Published: September 2023

Charge distributions at electrode-electrolyte interfaces play a crucial role in many electrochemical processes, some of which are electrocatalysis, supercapacitors, batteries etc., However, most experimental techniques, either microscopy or spectroscopy tools that are used to probe these systems, cannot provide any information about the interfacial spatial charge distribution. Techniques based on kelvin-probe force microscopy (KPFM) can provide some information, however they have a very limited depth of resolution and can only work with extremely dilute electrolytes. Recently, we developed a technique known as charge profiling three-dimensional (3D) atomic force microscopy (CP-3D-AFM) which could map out the charge densities at angstrom-depth resolution. The method is based on measuring 3D-AFM maps at different electrode potentials and further using electrostatic calculations to obtain the charge density depth profiles at the respective potentials. We used this method to measure charge distributions in highly ionic electrolyte systems and can explain their differential capacitance profiles. This CP-3D-AFM technique could enable to obtain molecular structural insights for a wide range of electrolyte systems and serve in designing principles for engineering effective electrode-electrolyte interfaces.
Photoelectrocatalytic Degradation of Cyanide Using TiO2 on Conducting Glass and Polarographic Analysis of the Products
Authors: Brüger Andreas
Published: September 2023

Cyanide used in gold mines is collected in tailing dams and has a high risk of contaminating the surrounding environment. Cyanide contaminations in the atmosphere, as well as in water and soil are insufficiently studied so far. The lack of interest, the complexity of the reaction mechanisms and the challenging analysis of the products are major reasons for this deficiency. The circumstance that a prominent part of cyanide is volatilsed during and after the gold extraction is often neglected; volatalised HCN is said to be sufficiently destroyed by the sunlight and the oxygen of the atmosphere which can easily be disproved by analysis of the cyanide content in the contaminated atmosphere. The investigation of the products of cyanide decomposition is an essential part in the evaluation of the toxicity originating from effluents of gold processing. In this work, spray pyrolysed TiO2 on conducting glass is used for the photoelectrocatalytic treatment of cyanide. In UV-A irradiating the catalyst and applying an external bias for the separation of the charge carriers, the cyanide is oxidised in solutions of different pH. The cyanide content after the process as well as the quantity of the products is analysed via polarography. Besides the oxidation, hydrolysis was detected as well, correlating to the pH of the solutions. The proposed method allows the evaluation of the level of environmental contamination of gold processing as well as the analysis of products that result from decontamination processes in gold mines. Furthermore the photocatalytic capability of TiO2 for the decontamination of cyanide wastewaters is determined.
Turning the Wheel through the Ages
Authors: Smith Sam Jackson , Donnelly Dan J , Fei Matthew , Matzker Sage , Roger Sofia , Doan Jonathan , Smotkin Eugene S.
Published: September 2023

Methods for reliably generating alternating current via placing metal coils in a rotating magnetic field were discovered by two individuals almost simultaneously: Italian engineer and physicist, Galileo Ferraris, and Austrian-American engineer, Nikola Tesla. While Tesla attained the patent for the AC-generator, Ferraris, who published the discovery a few months prior, is credited with having paved the way for the modern-day alternator, now used ubiquitously.

The origins of rotational energy conversion can be traced back to sugar plantations in the 1600s. At that time, the milling process was initially sustained through slave-driven turning of a wheel, which was geared to large wooden rollers that would squeeze sugar cane. The Caribbean and South American variant of this system was known as a trapiche, which employed three geared rollers. Over time, slaves were replaced with oxen and horses, which were eventually supplanted by water wheels and finally by steam engines. The water wheels implemented for sugar milling ultimately paved the path for creating electrical currents. Water turbines for hydroelectric power subsequently took off. Principles of steam engine operation were adapted for electrical power as well, ultimately culminating in the use of nuclear plants to generate “wheel” turning for electricity.

Electricity and magnetism, as well as interactions between them, are frequently discussed in introductory undergraduate physics. However, practical applications of these principles are often omitted from lectures. If taught under an experiential environment, these concepts can be introduced at even the middle school level, taught by first year college students taking basic college physics - a synergistic learning environment. With this in mind, we developed a middle school kit consisting of simple 3D-printed components, recycled DVDs and four bearings for support of 4 mm nail shafts. Enameled wire (30 AWG) is used to prepare the wire-wound coils. A large rubber band is used as the pulley-belt. The above represents the generator component. The power use component is assembled on an accompanying bread board. Power processing is demonstrated using diodes for rectification to DC. The DC power is used to recharge a 3V, 40 mAh lithium-ion coin cell. AC power from the generator can also be directly applied to load resistors. Students will be able to see the effects of varying the load by changes in the time of the free rotation of the generator wheels. Students will experience the charge and discharge of batteries with safe voltages and currents.

Middle school students will record data from the generator and conditioning systems and draw conclusions on worksheets that accompany the hardware.
(Invited) Grahame Symposium: Separating and Moving Charges through Functional Metal-Organic Frameworks
Authors: Hupp Joseph
Published: September 2023

In line with the longstanding physical electrochemistry interests and numerous innovative contributions of Grahame Award recipient Dr. Keith Stevenson, this presentation will focus on a physical electrochemistry problem: how to separate redox-hopping based hole-transport within porous, electrocatalytic metal-organic framework coatings from transport of charge-compensating ions through the same coatings. In principle, either process, or both, could define transport rates. For electrocatalysis, the general goal is to achieve the fastest transport possible. Wall-jet electrochemistry – the approach used here – offers a useful way of assessing redox-hopping rates without complications from ion ingress or egress. The wall-jet approach turns out to be especially useful when samples cannot be made compatible with RDE or IDE assemblies.
(Invited) Single-Molecule Electrical Currents Associated with Valinomycin Transport of K+
Authors: Schmeltzer Alexandra J. , Harris Joel M. , White Henry S.
Published: September 2023

A quantitative description of ionophore-mediated ion transport is important in understanding ionophore activity in biological systems and developing new ionophore applications. We present the direct measurement of the electrical current resulting from K+ transport mediated by individual valinomycin (val) ionophores. Step fluctuations in current measured across a 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) bilayer suspended over a ~400 nm radius glass nanopore result from dynamic partitioning of val between the bilayer and torus region, effectively increasing or decreasing the total number of val present in the membrane. Approximately 30 val are present in the membrane on average with a val entering or leaving the bilayer approximately every 50 seconds, allowing measurement of changes in electrical current associated with individual val. The single-molecule val(K+) transport current at 0.1 V applied potential is (1.3 ±0.6)×10-15 A, consistent with estimates of the transport kinetics based on large val ensembles. This methodology for analyzing single ionophore transport is general and can be applied to other carrier-type ionophores.
Electrical Circuit Tools for Simulating Student Lab Exercises on Electrochemical Processes
Authors: Fafilek Guenter
Published: September 2023

In 2020, SarsCov2 pandemic imposed severe restrictions for practical student courses. In our course on chemical engineering one topic is corrosion and corrosion protection. However, lock-down prohibited regular laboratory work where students could acquire their own experimental data. As a workaround, the simulation of electrochemical experiments on corrosion systems provided data, which allowed the illustration of basic corrosion principles and further evaluation and discussion. For that purpose, a Pspice(C) electrical circuit simulation environment has been chosen.

This contribution presents specifically designed electrical circuit models for electrochemical processes. Their combination to larger equivalent circuits for the whole system can deliver realistic and individual data for the students. With this software students learn about the components of an electrochemical cell and their behavior similar to a real experiment.

Figure 1
In-Operando Oxygen Evolution Reaction Electrocatalysis in Acidic Media
Authors: Skidmore Kayleigh , Brinkert Katharina , Walton Richard , Clayton Jasmine
Published: September 2023

The transition from fossil fuels to renewable sources requires the utilization of green hydrogen. Electrolysis is one of the areas gaining support within both government and industry spheres, due to the possibility of producing hydrogen using renewable energy sources at a high gas purity and current density. Despite significant interest in proton-exchange membrane (PEM) electrolysis, the oxygen evolution reaction (OER) at the anode is considered one of the main bottlenecks due to the sluggish electrode kinetics and the instability of many electrocatalysts in acidic electrolytes. This is because it is a four electron reaction with a high activation barrier, and so new active electrocatalysts are needed, which in turn needs a mechanistic understanding to target new materials. In-operando studies can be used to advance the mechanistic understanding of the reaction and shed light into rate-limiting steps as well as elucidate on potential structural changes of the electrocatalysts during the reaction.

Here, we report on a modified electrochemical cell for in-operando X-ray diffraction (XRD) studies of the OER using a calcium iridium pyrochlore (Ca2-xIr2O6·H2O) electrocatalyst spray-coated onto Toray carbon paper. 1 Whilst electrochemical techniques such as chronoamperometry and cyclic voltammetry are utilized in acidic electrolyte (0.1 M H2SO4), changes to the catalyst surface and degradation rates are monitored by XRD. This provides an overall picture of phase and crystallinity changes of the iridium pyrochlore throughout the OER. X-ray absorption near edge spectroscopy (XANES), complementary to XRD, is carried out to further determine the iridium oxidation state changes during the catalytic process. The catalyst is furthermore assessed ex-situ by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) in both, pre- and post-electrochemical experiments, to examine changes to its morphology and surface composition. Appropriate cell modifications accounting for mass transport as well as gas bubble formation at the working electrode surface are developed following commercial electrolysis cell designs. This allows studying both, catalyst activity and stability, under realistic operation conditions that is currently unprecedented in the literature.

References:

Burnett, D. L. et al. Exploiting the flexibility of the pyrochlore composition for acid-resilient iridium oxide electrocatalysts in proton exchange membranes. Journal of Materials Chemistry A
9, 25114–25127 (2021).
Oxygen Reduction on Organic Mixed Ionic-Electronic Conducting Polymer Electrodes
Authors: Mefford J. Tyler , De La Fuente Duran Ana , Penn Emily E , Liang Allen Yu-Lun , Marks Adam , Chueh William C. , Salleo Alberto , Giovannitti Alexander
Published: September 2023

Organic mixed ionic-electronic conductors (OMIECs) are a class of conjugated semiconducting polymers with tunable electronic and ionic transport properties enabled through polaron-forming ion insertion redox reactions. The energy to form these conductive polaronic states can be controlled through rational design of the polymer backbone to enable predominantly electron/cation (n-type) or hole/anion (p-type) transport. Simultaneously, electrolyte uptake into the bulk of the electrode can be controlled through incorporation of polar/non-polar sidechains. The ability to tune the energy of the redox-active states, the majority charge carrier, and the local reaction environment offers an opportunity to independently optimize activity and selectivity in electrochemical energy conversion processes with a single-phase electrode.

In this talk, I will discuss our efforts to develop OMIECs as electrocatalysts for the oxygen reduction reaction. The electronic and chemical origins of reactivity are interrogated through pH-dependent electroanalytical characterization, operando spectroscopy, charge-transport measurements, and ab initio/microkinetic simulations. The nature of the polaronic states provide a generalized framework to understand pathway selectivity towards the 2-electron H2O2 or 4-electron H2O product and serve as a design principle in developing this emerging class of metal-free electrocatalysts.
Available and Cheap Methodology for Accurate Onset Potential and Tafel Slope Determination of Earth-Abundant Water Oxidation Electrocatalysts
Authors: Seijas Da Silva Alvaro , Sanchis-Gual Roger , Otero Toribio , Coronado Eugenio , Abellán Gonzalo
Published: September 2023

To date, a plethora of electrocatalysts for the Oxygen Evolution Reaction (OER) have been proposed. For evaluating their electrocatalytic behaviour the determination of the onset potential and Tafel slope in each studied electrolyte are key parameters.[1] Nevertheless, this evaluation becomes particularly problematic for first-transition metal catalysts as well as by the use of electroactive collectors whose redox peaks overlap the onset potential and hinder the correct determination of Tafel slope.[2] A usual solution to solve this problem is the in-situ determination of generated oxygen by mass spectrometry.[3]

However, this in-situ determination is very expensive and only available in few laboratories. To overcome these limitations, coulovoltammetric response obtained from cyclic voltammetry allow a quantitative separation in the same potential range of the charge consumed by reversible (redox peak) reactions and the charge consumed by the irreversible reaction: the oxygen release. Accordingly, by means of quantifying the irreversible charges for different anodic potential limits is possible the unambiguous determination of both, the onset potential and the Tafel slope values isolating the catalyst redox contributions. To demonstrate the use of this technique, the onset potential and the Tafel slope for three benchmark electrocatalysts based on first-transition metal: a layered double hydroxide, a Prussian blue analogue and a β-Layered hydroxide were determined.[4] This study evidence the potential of coulovoltammetry as a straightforward and powerful tool for the investigation of electrocatalytic performances.

References

[1] Fenglei Lyu, Qingfa Wang, Sung Mook Choi and Yadong Yin, Fenglei Lyu. Small,
2019, 15, 1804201.

[2] Alvaro Seijas-Da Silva, Víctor Oestreicher, Eugenio Coronado and Gonzalo Abellán. Influence of Fe-clustering in the water oxidation performance of two-dimensional layered double hydroxides. Dalton Trans., 2022, Accepted Manuscript.

[3] Dr. Kaiyue Zhu, Prof. Xuefeng Zhu and Prof. Weishen Yang, Angew.
Chem. Int. Ed.
2019, 58,1252 –1265.

[4] Roger Sanchis-Gual, Alvaro Seijas-Da Silva, Marc Coronado-Puchau, Toribio F.Otero, Gonzalo Abellán, Eugenio Coronado, Electrochimica Acta,
2021, 388, 138613.

Figure 1
Spontaneous Oxygen Reduction on Perovskite Oxide Surface in Aqueous Medium
Authors: Bosse Jan , Akbashev Andrew
Published: September 2023

Oxygen reduction/evolution reactions (OER/ORR) do not normally occur spontaneously at room temperature. Here, we will demonstrate that a perovskite oxide can drive a spontaneous ORR in aqueous media. Our experiments show that spontaneous ORR, while taking place at open-circuit conditions, results in a severe oxidation of the surface and causes cation leaching, oxygen intercalation and gradual dissolution of the perovskite. Using DFT and molecular dynamics simulations of the perovskite-electrolyte system, we propose a possible mechanism for this highly unusual phenomenon. Likely, a spontaneous ORR is connected with the emergence of a specific atomic configuration at the surface that stabilizes reaction intermediates and reduces activation barrier(s) for the ORR.
Mechanism of Water Dissociation on Metal Oxide Surfaces in Bipolar Membrane Electrolyzers: A First-Principles Calculation
Authors: Debela Tekalign Terfa , Hendon Christopher , Boettcher Shannon W.
Published: September 2023

Bipolar membranes for water electrolysis, consisting of an acidic cation exchange layer and an alkaline anion exchange layer are a promising means for hydrogen production. The electrolyzer operates the oxygen evolution reaction (OER) under locally basic conditions and the hydrogen evolution reaction (HER) under locally acidic conditions. Water dissociation (WD) occurs within the junction, which is spatially separated from the HER and the OER. It has been shown that the addition of a layer of metal oxide nanoparticles at the junction significantly lowers the overpotential for the process of WD [Science, 2020, 369,1099]. However, the atomistic mechanism by which the metal oxide surface catalyzes the WD is still unclear. We will discuss the theoretical understanding of the WD mechanism at the metal-oxide/water interfaces and investigate the descriptors such as surface pKa, dielectric constants, and adsorption energies, etc. We will combine ab intio molecular dynamics simulations with the electronic structure calculations at the hybrid functional level. Further details of the reaction mechanisms during the WD process will also be explored with the nudged-elastic-band calculations.
First Principles Investigations of Electrocatalyst Design for Mg-CO2 Batteries
Authors: Islam Mahbub
Published: September 2023

Carbon di-oxide (CO2) is the leading greenhouse gas responsible for global warming and catastrophic consequences on environmental imbalance. Metal-CO2 batteries have grabbed significant attention in the scientific community because of the unique feature of simultaneously consuming CO2 for the production of green electricity. In this regard, Mg- CO2 battery is especially highly promising because of its high volumetric capacity, low-cost, natural abundance. However, several roadblocks such as sluggish reaction kinetics of CO2 reduction, poor reversibility during charging and discharging cycles, and high charge overpotential needs to overcome the practical realization of Mg-CO2 batteries. The target performance of Mg-CO2 batteries can only be achieved through developing efficient cathode catalysts. In this study, we employ first-principles density functional theory (DFT) calculations to screen for electrocatalysts to achieve expedited reaction kinetics. Single-atom catalysts (SACs) are atomically dispersed metal atoms on a substrate and have evolved as an established strategy for ensuring the maximum utilization of catalytically active atoms in heterogeneous catalysis. The high throughput DFT simulations will be leveraged to understand the adsorption behavior of the reaction intermediates of Mg-CO2 batteries on the SACs. The derived free energy profile will illustrate the favorable reaction pathways to identify high performing SACs. The screening will be spanned over the first two rows of the transition metals.
(Invited) Direct Probe of Electrochemical Pseudocapacitive pH Jump at a Graphene Electrode
Authors: Wang Yongkang , Seki Takakazu , Bonn Mischa , Nagata Yuki
Published: September 2023

Molecular-level insight into interfacial water at buried electrode interface is essential in electrochemistry, but spectroscopic probing of the buried interfaces remains challenging. Here, using surface-specific heterodyne-detected sum-frequency generation (HD-SFG) spectroscopy, we directly access the interfacial water in contact with the graphene electrode supported on calcium fluoride (CaF2). The HD-SFG signal is obtained by overlapping the infrared and visible pulses at the sample position. An SFG signal is enhanced when the infrared frequency is resonant with the molecular vibration. The HD-SFG can provide the information on the orientation of the interfacial molecules. With the molecular specificity, orientational specificity, and surface specificity of the HD-SFG, we clarify the molecular level insight into the structure of the electrified graphene-water interface. At the negative voltage, we found the negative HD-SFG peak at 3630 cm-1, which manifests that the O-H group points to the bulk water, not to the CaF2 supported graphene. This O-H group is the Ca-O-H group, indicating that the chemical reaction occurs at the CaF2 surface. By monitoring the variation of the HD-SFG spectra upon the various applied potential, We find phase transition-like variations of the HD-SFG spectra. We attribute such a variation not to charging/discharging of graphene but to charging/discharging of the CaF2 substrate through the pseudocapacitive process. The potential-dependent spectra are nearly identical to the pH-dependent spectra, evidencing that the pseudocapacitive behavior is associated with a substantial local pH change induced by water dissociation between the CaF2 and graphene. Our work evidences the local molecular-level effects of pseudocapacitive charging at an electrode/aqueous electrolyte interface.
Probing Molecular Structures at Electrified Interfaces Using in-Situ Surface-Enhanced Raman Spectroscopy
Authors: Kim Jaehyeon , Zhao Fujia , Zhou Shan , Panse Kaustubh S. , Zhang Yingjie
Published: September 2023

The molecular scale understanding of electrode-electrolyte interfaces is significant, as interfacial molecular structures play a critical role in determining various properties such as capacitance and catalytic activity. However, the limited understanding exists on the interfaces, especially at a molecular level, due to difficulties to selectively probe the interfaces without an interference from the bulk. In this talk, I will present our recent observations on molecular configurations at electrified interfaces using in-situ surface-enhanced Raman spectroscopy (SERS). To be specific, we study interfaces of ionic liquids and aqueous electrolytes, considering they are promising candidates for various electrochemical applications. Our SERS spectra display a strong enough interface-sensitivity providing comprehensive information on a potential-dependence of ion configurations such as molecular position and orientation. We expect the molecular scale understandings provided by our studies are beneficial to a wide range of electrochemical applications including supercapacitors, batteries, and electrocatalysts.
(Invited) Probing the Specific Adsorption of Alkali Metal Cations on Au Electrodes Under CO2 Reduction
Authors: Waegele Matthias M.
Published: September 2023

Electrolyte engineering has recently been recognized as an integral component in the design of electrode/electrolyte interfaces for electrocatalysis. In particular, alkali metal cations of the supporting electrolyte are known to influence electrocatalytic processes. A better understanding of these cation effects requires methods capable of probing the distribution of alkali metal cations in the electrochemical double layer under reaction conditions. However, the scarcity of experimental technique capable of probing alkali metal cations greatly hinders further advances in leveraging cation effects in electrolyte engineering. In this talk, we will discuss our novel spectroscopic approach for quantifying the surface coverage of specifically adsorbed alkali metal cations, that is, the cations that are in direct contact with the electrode and therefore most likely to influence electrocatalysis. The technique is based on the use of an organic cation, tetramethylammonium (methyl4N+), as a vibrational probe of the electrode/electrolyte interface in the presence of alkali metal cations. We will discuss how we use this approach to characterize the adsorption of alkali metal cation during CO2-to-CO conversion.
Characterization of Porous Transport Electrodes in Proton Exchange Membrane Water Electrolyzers with Scanning Electron Microscopy and Micro X-ray Computed Tomography
Authors: Pylypenko Svitlana , Stelmacovich Genevieve , Khandavalli Sunilkumar , Paxson Adam
Published: September 2023

With the move towards commercialization of proton exchange membrane water electrolyzers (PEMWE’s), the integration of the porous transport layer (PTL) and the anode catalyst layer (CL) into the porous transport electrode (PTE) is of much interest. Specifically, it is important to understand how different CL fabrication routes and ink formulations affect the performance. In addition to electrochemical characterization, a visual understanding of all components and the CL/PTL interface is needed to identify most optimum fabrication conditions.

Typically, the CL is deposited on the polymer membrane, and then integrated with PTL. Deposition of the CL onto PTL has certain advantages, but generally results in CL with variation in coverage and thickness. Depending on the catalyst loading, this can range from very thin layers on the order of several hundred nanometers, to thicker coatings on the order of tens to hundreds of microns. Typically, characterization techniques such as Scanning Electron Microscopy Electron combined with X-Ray Dispersive Spectroscopy (SEM-EDS), is used in correlation with performance testing for initial assessment of the coating heterogeneity. Top-down analysis and analysis of cross-sections are both commonly employed. Other SEM-based techniques are also used, including Focused Ion Beam (FIB) technique, which can provide information about internal structure. Micro X-ray Computed Tomography (XCT) is another powerful method for investigation of CLs and their integration with PTLs 1. Thinner CLs produced with low catalyst loadings are inherently more challenging to characterize and require multi-analytical approach.

This work investigates a series of PTEs produced using a Meyer Rod method. Fabrication parameters such as rod size, ink formulations and catalyst loadings were varied resulting in changes in the quality of the CLs. SEM-EDS and synchrotron micro-XCT (at the Advanced Photon Source (APS) on beamline 2-BM) were used to assess CL distribution, homogeneity, and thickness. This talk will discuss both benefits and limitations of using micro-XCT on these materials and compare techniques to highlight the benefit of using multiple characterization techniques for analysis.

Citations:

(1) Leonard, E.; Shum, A. D.; Danilovic, N.; Capuano, C.; Ayers, K. E.; Pant, L. M.; Weber, A. Z.; Xiao, X.; Parkinson, D. Y.; Zenyuk, I. V. Interfacial Analysis of a PEM Electrolyzer Using X-Ray Computed Tomography. Sustain. Energy Fuels
2020, 4 (2), 921–931.
Uncovering Electrochemical Cation-Storage Mechanisms in Defective Vanadium Ferrites Using Synchrotron-Quality, in-Lab X-Ray Absorption Spectroscopy
Authors: DeBlock Ryan H. , Ford Hunter O. , Chervin Christopher N. , Rolison Debra R. , Johannes Michelle D. , Long Jeffrey W.
Published: September 2023

X-ray absorption spectroscopy (XAS) is a critical tool for investigating new materials for electrochemical energy storage, providing important information on metal oxidation state and element-specific coordination. Historically, XAS measurements had required the energy specificity and brilliance of a synchrotron facility, but recent advances in detectors and optics are bringing XAS capabilities to the laboratory setting with multiple commercial instruments available. At the Naval Research Laboratory, we use laboratory-based XAS to study a class of disordered vanadium ferrite (VFe2Ox) aerogels that exhibit promising performance for electrochemical energy-storage applications such as rechargeable lithium-ion batteries.1,2 The structure and composition of these materials are readily varied via modifications to the epoxide-promoted sol–gel reaction of iron chloride and vanadium isopropoxide (e.g., substitution with other cations such as Al3+),2 as well as post-synthesis thermal treatments that render disordered, defective, or nanocrystalline forms of a given composition. The resulting series of VFe2Ox materials are evaluated by XAS in both ex situ and in situ configurations, including as powder-composite cathodes versus lithium metal in pouch cells with conventional nonaqueous lithium-ion electrolyte. X-ray Absorption Near-edge Spectroscopy (XANES) at the V K-edge and Fe K-edge is used to track V and Fe oxidation state, respectively, permitting the assignment of metal-centered redox across the broad potential range over which these materials are electrochemically active (2–3.4 V vs Li/Li+). Extended X-ray Absorption Fine Structure (EXAFS) analysis provides information on V- or Fe-specific coordination as a function of composition, structure, and state-of-charge. Parallel computation efforts using Density-Functional Theory offer a complementary feedback loop with experimental XANES and EXAFS to achieve a sophisticated description of these complex battery materials.

1. C. N. Chervin, J. S. Ko, B. W. Miller, L. Dudek, A. N. Mansour, M. D. Donakowski, T.

Brintlinger, P. Gogotsi, S. Chattopadhyay, T. Shibata, J. F. Parker, B. P. Hahn, D. R.

Rolison, and J. W. Long, J. Mater. Chem. A
3, 12059 (2015).

2. C. N. Chervin, R. H. DeBlock, J. F. Parker, B. M. Hudak, N. L. Skeele, J. S. Ko, D. R.

Rolison, and J. W. Long, RSC Adv.
11, 14495 (2021).
(Best Student Presentation) Impact of Surface Characteristics on Interfacial Stability in Lithium Metal Batteries
Authors: Morey Madison , Ryan Emily
Published: September 2023

A comprehensive understanding of the morphology evolution of deposited lithium (Li) is a primary challenge in the commercialization of Li-metal batteries. Li-metal batteries, which contain a Li-metal anode, have a theoretical capacity that is an order of magnitude greater than that of a Li-ion battery helping to overcome their energy storage limitations. However, while Li-metal batteries have proven to have a much larger specific capacity, they are hindered by unstable deposition at the electrode-electrolyte interface and severe dendritic growth. Interfacial stability is a complex phenomenon that is influenced by many different factors, including local current densities, overpotentials, Li+ concentrations, and transport properties. Additionally, varying surface characteristics such as surface chemistries and the physical structure of the anode can affect Li deposition and could be used to design a more stable interface. Due to the nature of the anode surface, it is difficult to observe the complex physics experimentally. Thus, computational modeling is a powerful tool for understanding the deposition of Li on the anode surface. In this work we present a computational model to comprehensively study the morphology of dendrites when exposed to varying conditions. While transport properties1, electrolyte characteristics2, separator structures3, and charging protocols4 play significant roles in Li dendrite morphology and interfacial stability, this work focuses on the impact of the anode surface itself on stability. This includes patterned anode surfaces for guided lithium deposition and varying surface chemistries such as surface energy and reaction rate. We concentrate on the types of defects that are present along the anode surface including surface roughness, points of high convexity, breaks in the SEI layer, lattice defects leading to changes in surface energy and their impact on instability. We also look at guided deposition through modifications of the anode surface.

1. J. Tan, A. M. Tartakovsky, K. Ferris, and E. M. Ryan, J Electrochem Soc, 163, A318–A327 (2016).

2. J. Tan and E. M. Ryan, J Power Sources, 323, 67–77 (2016).

3. A. Cannon and E. M. Ryan, ACS Appl Energy Mater, 4, 7848–7861 (2021).

4. T. Melsheimer, M. Morey, A. Cannon, and E. Ryan, Electrochim Acta, 433 (2022).
Nanoengineered Carbon Surfaces for Ultrasensitive Neurochemical Detection
Authors: Ross Ashley E , Ostertag Blaise J
Published: September 2023

Hypothesis-driven methods to tailor the functionality, topology, carbon orientation, and three-dimensional (3D) structure of carbon microelectrodes, for specific classes of neurochemicals, would significantly improve analyte specificity and lower the limits of detection for fast-scan cyclic voltammetry (FSCV) detection in the brain and beyond. FSCV at carbon-fiber microelectrodes is an established technique to study the signaling dynamics of many different neurochemicals in the brain. Despite its widespread applicability to many analytes, most in vivo studies are conducted on bare, unmodified carbon-fiber microelectrodes and many of the fundamental studies of new electrode materials focus on dopamine detection. Manipulations of the carbon surface can have profound effects on electrochemical detection and carefully controlled experiments to manipulate the analyte-electrode interface could provide exquisite information for future design of electrode materials. Here, we will discuss our latest work on synthesizing and manipulating the surfaces of carbon-based materials including graphene-based fibers and porous PAN-derived carbon-fiber, to exploit specific neurochemical-electrode interactions for improved detection. This presentation will demonstrate the importance of understanding the analyte-structure-electrode-surface interface for designing optimal electrodes.
Stability of N-Heterocyclic Carbene Monolayers Under Continuous Voltammetric Cycling
Authors: Arroyo Netz
Published: September 2023

N-heterocyclic carbenes (NHCs) are promising monolayer-forming chemistries that can overcome limitations of thiol-based monolayers in terms of stability, surface functionality and reactivity across a variety of transition metal surfaces. Recent publications have reported the ability of NHCs to support biomolecular receptors on gold substrates for sensing applications, and improved tolerance to prolonged biofluid exposure relative to thiol chemistries. However, important questions remain regarding the stability of these monolayers when subjected to voltage perturbations, which is needed for technology application in electrochemical platforms. In response, we investigated the ability of two NHC chemistries, 1,3-diisopropylbenzimidazole and 5-(ethoxycarbonyl)-1,3-diisopropylbenzimidazole, to form monolayers via self-assembly from methanolic solutions of their trifluoromethanesulfonate salts. We compared the electrochemical behavior of the resulting monolayers relative to that of benchmark mercaptohexanol monolayers in phosphate-buffered saline. In this presentation I will discuss the results of this study and how they can affect future use of NHCs in electrochemical biosensors.
Enzymatic Electrochemical Immunoassay Utilizing Magnetic Beads for Detection of Preterm Birth Biomarkers
Authors: Owens Olivia E. , Buckey Grace , Cliffel David E
Published: September 2023

The mechanisms that preclude preterm birth are largely unknown. Studying the concentration changes of known preterm birth protein biomarkers in response to infections can help elucidate these mechanisms. The development of sensors for two potential biomarkers, matrix metalloproteinase 3 (MMP-3) and interleukin-1beta (IL-1β), will aid in such studies. IL-1β is an inflammatory cytokine that assists in initiating the inflammatory response associated with birth while MMP-3 plays an essential role in degrading the fetal membrane, inducing labor. Both IL-1β and MMP-3 are known to be present during a healthy birth, but when prematurely induced, can result in preterm birth.

Magnetic bead-based competitive and sandwich assays are being developed to detect concentrations of IL-1β and MMP-3. These sensor designs utilize Horseradish peroxidase (HRP)/3,3′,5,5′-Tetramethylbenzidine (TMB) as the enzyme/substrate pair. Magnetic beads are modified with the antibody of interest and subsequently reacted with the target protein. In the competitive assays, the target protein is tagged with HRP; in the sandwich assays, a detection antibody is reacted with the target protein and subsequently tagged with HRP. When TMB is reacted with the modified beads, the HRP enzyme oxidizes TMB to TMB diimine which is then electrochemically reduced. The current generated in this process can be used to create a calibration curve with known protein concentrations versus current output. Current efforts are focused on improving sensitivity and replicability of the sensor designs. Future directions include monitoring the concentration of MMP-3 and IL-1 β before and after infection of an instrumental fetal membrane on-a-chip.
Scanning Local Redox on 10 Micron Spots on a Monolith Electrode to Quantify Multiple Analytes at 10 Attomolar Sensitivity with Dynamic Range of Seven Orders of Magnitude
Authors: Saraf Ravi , Saraf Akshat , Lim Jay Min , Prasad Abhijeet , Tevatia Rahul , Chan Alicia , Ruder Alexander
Published: September 2023

Electrochemical transduction is arguably the most prolific and impactful method to sense chemicals and biochemicals. For example, electrochemical methods have the distinct advantage to quantitatively measure nucleic acid (NA) sequences at a limit of quantification (LOQ) of 10 attomolars and high sequence specificity. The sensitivity and dynamic range significantly surpasses optical/spectroscopic, gravimetric, and electronic transduction methods. However, electrochemical sensing cannot be easily multiplexed. Only one analyte per electrode can be measured. Furthermore, the electrode size, i.e., the sensor area, for reasonable redox current, is typically, at least 1 mm2 for small analyte concentration.

A fully automated instrument, called the Scanning Electrometer for Electrical Double-layer (SEED), will be described that addresses the abovementioned limitations. SEED, based on differential optics, quantitatively measures electrochemical process by changes in the electrical double-layer (EDL) and the surface during electrochemical process. The instrument can be operated in three modes: (a) reflectivity; (b) interferometry; (c) spectroscopy. The instrument can be toggled between the three modes without moving the sample or realigning the optics. The three modes measure the structural change at the surface, change in charge state of the EDL, and change in the molecule’s electronic structure due to the electrochemical process.

The principle will be described with following applications in material science, sensing and life science: (i) miRNA profiling at LOQ of 10 attomolar with dynamic range of seven orders of magnitude; (ii) single base mutation in NA sequence; (iii) heavy metal ion detection from ppt to ppb levels; (iv) spectroscopic measurement during redox on graphene; (v) Langmuir adsorption of ions on Au electrode; and (vi) direct measurement of potential of zero charge (PZC).

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Quantitative Electrochemistry-Mass Spectrometry: Real-Time Detection of Volatile Products for Electrocatalysis and Batteries
Authors: Winiwarter Anna , Jensen Kim Degn , Novak Hartmann Johannes
Published: September 2023

A major challenge both within electrocatalysis and battery research concerns the real-time (i) identification and (ii) quantification of volatile reaction products as a function of the applied electrochemical parameters and the reaction conditions. Analysis of both steadily evolving gases and of fast- and transient reaction phenomena can reveal key insights into reaction mechanisms. To this end, methods like Differential Electrochemical Mass Spectrometry (DEMS)1 and On-line Electrochemical Mass Spectrometry (OLEMS)2 have been used successfully to study reaction mechanisms to an ever-increasing degree in recent years, primarily in aqueous electrolytes. Similarly, Online Electrochemical Mass Spectrometers (OEMS)3 have been essential for the study of gas evolution in batteries.

However, to gain an in-depth understanding of these mechanisms, the ability to accurately relate the electrochemical charge transferred in the reaction to the amount of evolved product is essential. To this end, accurate calibration of MS signals is paramount. Calibration procedures available for DEMS systems are by themselves cumbersome and unreliable and full quantification is not possible for OLEMS.

Herein, we show how a simple gas-based calibration procedure using chip-based Electrochemistry-Mass Spectrometry (EC-MS) can be used for reliable, fully quantitative real-time analysis of volatile electrochemical reaction products. We validate this calibration with electrochemistry-based calibration methods described previously.4,5 The new procedure allows to extend the quantitative analysis to systems with no a priori knowledge of faradaic efficiencies. We demonstrate calibration of important gases like H2, O2 and C2H4 in aqueous and non-aqueous electrolytes and exemplify the calibration methodology’s usefulness on standard electrochemical reactions.

References

H. Baltruschat, J Am Soc Mass Spectrom, 15, 1693–1706 (2004).

A. H. Wonders, T. H. M. Housmans, V. Rosca, and M. T. M. Koper, J Appl Electrochem, 36, 1215–1221 (2006).

N. Tsiouvaras, S. Meini, I. Buchberger, and H. A. Gasteiger, J Electrochem Soc, 160, A471–A477 (2013).

D. B. Trimarco et al., Electrochim Acta, 268 (2018).

S. B. Scott, PhD thesis, Technical University of Denmark (2019).

Figure 1: a) Schematic of the MS inlet chip’s working principle. b) Uncalibrated M2 and M32 signals (dotted lines) and the same signals after calibration for H2 and O2 (full lines) in a cyclic voltammogram of PtPoly in 0.1 M HClO4 obtained at room temperature at 20 mV/s.

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Enhanced Electrochemical Performance of Lithium Metal Batteries with Fluorine Doped SO2 Based Nonflammable Inorganic Electrolytes
Authors: Lee Jiwhan , Park Haeseok , Choi Seong Hoon , Seung Do Mun , Kim Hansu
Published: September 2023

With the demands for high energy density of lithium ion batteries(LIBs), replacing conventional anode of LIBs with lithium metal provide a great opportunity to overcome the limits of batteries because of their high-energy-density. However, utilizing lithium metal in battery system has problems like uncontrollable lithium dendrite growth during lithium plating/stripping and unstable solid electrolyte interface(SEI) on lithium metal which can cause short circuit of batteries. Fluorine is one of the well-known components to stabilize SEI layer in the battery system using commercial organic electrolytes. In this presentation, we introduce lithium metal batteries(LMBs) based fluorine doped LiAlCl4-xFx-3SO2 nonflammable inorganic liquid electrolyte to achieve stable SEI and uniform deposition of lithium. Compare to non-doped LiAlCl4-3SO2 electrolyte, the fluorine doped SO2 based inorganic electrolyte show much alleviated overpotential during cycling. We will show how fluorine doping in electrolytes impact the electrochemical performance of LMBs with SO2 based inorganic liquid electrolytes. Detailed reaction mechanism of our battery system with fluorine doped LiAlCl4-xFx-3SO2 nonflammable inorganic liquid electrolyte will be discussed in the presentation.
High Voltage Long-Lifetime Mild pH-Decoupling Aqueous Flow Battery with in-Situ pH Recovery
Authors: Xi Dawei , Alfaraidi Abdulrahman , Gao Jinxu , Cochard Thomas , Faria Luana Italiano , George Thomas Young , Amini Kiana , Sosa Jordan D. , Wang Taobo , Liu Richard , Gordon Roy G. , Aziz Michael J.
Published: September 2023

Aqueous redox flow batteries (ARFBs) are being developed for grid scale electricity storage. However, the 1.23 V water splitting window makes the development of a long lifetime high-voltage ARFB challenging. Though the pH-decoupling design, with an acidic posolyte and an alkaline negolyte has been demonstrated to broaden the operating voltage window, long term operational stability and overall energy efficiency are penalized because of acid-base leakage along the pH gradient. Mild acid and base are used as supporting electrolytes to diminish proton and hydroxide crossover rates, resulting in higher overall energy efficiency. An acid-base in-situ regeneration system is implemented to restore the negolyte and posolyte pH to starting values. The capacity fade rate achieved is < 0.08%/day, with > 75% overall energy efficiency, and the Coulombic efficiency is around 99%. This work demonstrates a possibility of solving the critical issues (lifespan, rate capability, long term practicability and energy efficiency) for pH-decoupling ARFBs and guides the design for next generation high voltage ARFBs.