bluuebunny/crossref_metadata_2025 huggingface dataset:
A Voltammetric Investigation of the Electrocatalytic Cycle Mechanism of Fe(I) and Mn(I) Complexes
Authors: Legaspi Kristine , Soto Jonathan , Tang Tianhua , Sigman Matthew , Minteer Shelley , Smith Diane
Published: September 2023

Earth-abundant, first row, low coordinate transition metal complexes are promising candidates for the electrocatalysis of a variety of organic synthesis reactions. However, transition metal complexes in the M(I) state have the propensity to undergo disproportionation, hindering their ability to carry out the electrocatalytic cycle. In this study, we seek to identify and understand the mechanism by which the M(I) complexes may act as an electrocatalyst for a simple organic coupling reaction, beginning with the radicalization of benzyl bromide as a representative starting material. Initial characterization of the complex and its components by cyclic voltammetry demonstrate general stability of the catalyst, while equivalent additions of benzyl bromide exhibit the execution of the electron transfer and radical generation. Cyclic voltammetry simulations provide supplementary guidance into the relationship between benzyl bromide and the catalyst. Additional experiments conducted using analytical techniques such as mass spectrometry, x-ray spectroscopy, and nuclear magnetic resonance help to further characterize portions of the proposed mechanism and supporting details. Analysis to date suggests that the model electrocatalytic cycle is interrupted to an extent, with contributions from both disproportionation and substituted coordination at the transition metal center. Experimental and simulated voltammograms are qualitatively consistent with this proposed catalytic cycle interruption.
(Invited) Molecular Reaction Imaging of Charge Transport in MoS2 Nanoflake Photoelectrodes
Authors: Sambur Justin
Published: September 2023

Transition metal dichalcogenides (TMD) such as WSe2 and MoS2 are highly efficient and stable light absorbers in TMD∣I−,I3
−∣Pt liquid junction solar cells. It is generally accepted that TMD crystals with a large fraction of exposed edge sites exhibit lower power conversion efficiencies (PCEs) than apparently smooth crystals. However, one open question is why does the PCE vary significantly from one crystal to another? Answering this critical question could lead to robust syntheses for high quality and uniform TMD samples. In this work, we apply nanoscale photoelectrochemical microscopy techniques to study n-type TMD nano flake∣I−,I3
−∣Pt cells. Using a combination of near-diffraction-limited photocurrent mapping and molecular reaction imaging techniques, we reveal a previously hidden surface recombination process: photogenerated holes in hidden p-type domains travel micron-scale distances parallel to the solid/liquid interface and preferentially react with iodide at step-edges. The overall efficiency of the nanoflake, as evidenced from whole nanoflake-level photoelectrochemical measurements, is dictated by the size, efficiency, and location of n- and p-type domains. These results provide a unifying view of efficiency losses in smooth TMD photoelectrodes and open the possibility to design electrode architectures that leverage the long-range lateral charge transport property for photoelectrocatalysis.
Different Approaches to Teaching Electrochemistry and Equilibria II - Updates and Aftermath®
Authors: Coduto Joshua Richard , Lazicki Andy Peter , Paschkewitz Timothy , Leddy Johna
Published: September 2023

Instruction in electrochemistry and equilibria was once algebraically intensive. But the skills of contemporary undergraduates have changed. Instruction has shifted to spreadsheets, web searching, and mathematical manipulators (e.g., Wolfram Widgets®). Emphasis on methods of problem solving requires full access to web tools, open book/ open computer exams, and new ways to present data.

For electrochemistry and equilibria, tools include systematic treatment of equilibria + Wolfram Widgets to complete the algebra once the system is specified; potential axes to identify spontaneous reactions and pH dependence; and spreadsheets tailored to various classes of titrations that are developed by the students with video supplements.

Here, several newly deployed tools for undergraduate instruction are briefly introduced. The commercial tools are available at little or no cost.

Wolfram Widgets®

“Walk the Duck”

Voltammetry i vs E and Ohm’s law

Merge Cubes® for display of 3D data

AfterMath cyclic voltammetric simulations (Pine Research)

ProWriting Aid® and BibCitation®

Tools are provided to allow students to “See the Beaker” and to encourage the students to speculate about chemical systems and test their ideas.

Acknowledgments: Work supported by the Carver Foundation and Innovations in Teaching with Technology Awards (ITTA) at the University of Iowa
In Situ Synthesis of Co-WO3 Anodic Layers for Enhanced Photoelectrochemical Water Splitting
Authors: Syrek Karolina , Zycha Marta , Kotarba Sebastian , Sulka Grzegorz
Published: September 2023

Photoelectrochemical water splitting under solar radiation is one of the most studied areas of science. However, there are still many problems connected with this topic such as the low efficiency of systems or their usability only in the region of ultraviolet radiation. Anodic metal oxides are used as working electrodes in PEC cells due to their unique geometry, relatively high surface area, simple preparation, and their unique properties. Nanostructured tungsten oxide is characterized by strong photocorrosion stability in aqueous solutions and stable physicochemical properties. The main advantage of this material is its bang gap energy (2.6 eV), which is much lower than that of the commonly used titanium dioxide (3.2 eV). In consequence, absorption in the visible light region is significantly increased (up to 12% of the solar spectrum). The main objective of this project is to develop and optimize the single-step fabrication method of cobalt-doped nanostructured anodic tungsten oxide with enhanced photoelectrochemical properties under solar radiation. Particular attention will be paid to finding the correlation between the concentration of Co2+ ions in the electrolyte and their amount embedded in the anodic layer. A complex characterization (SEM/EDS, XRD, XPS, UV-Vis DRS) of nanostructured Co-WO3 layers will be performed to establish correlations between material morphology, composition, structure, and its optical, semiconducting, spectro-, photo- and electrochemical properties.

Acknowledgements

This research was partially funded within the budget of the "Excellence Initiative - Research University" program at the Jagiellonian University in Krakow.
Operando Microscopy of Model Electrocatalysts during Oxygen Evolution Reaction
Authors: Akbashev Andrew
Published: September 2023

In situ characterization of electrochemical processes in model materials are central to fundamental electrochemistry as they provide precise potential-dependent quantities that can be used to accurately assess theoretical models and predictions. As such, structural evolution of materials under highly oxidizing conditions represents a particular challenge. To gain the necessary insight into the surface and bulk behavior, one should combine advanced in situ characterization techniques with well-defined materials that are essential for modeling.

In this talk, I will discuss how a combination of in situ microscopy techniques can provide insight into the surface and bulk behavior of electrocatalysts during electrocatalytic water splitting (OER). Specifically, I will show how operando electrochemical atomic force microscopy (EC-AFM) can be used to record nanoscale changes in the surface morphology during anodic corrosion of the perovskite SrIrO3 surface. I will also discuss how operando EC-AFM can be combined with operando transmission X-ray microscopy and scanning electrochemical cell technique to probe the evolution and reactivity of single particles of Co(OH)2.
Voltage Controlled Ab-Initio Simulations of Metal-Insulator Interfaces Immersed in Electrolyte for Corrosion and Battery Applications Via the Quantum Continuum Approximation (QCA)
Authors: Campbell Quinn
Published: September 2023

While Density Functional Theory (DFT) has been an invaluable tool for exploring atomic interaction of defects and interfaces, it has been difficult to include information about the voltage of the larger electrochemical system into these calculations. This is because the electric field at any given simulation region is dependent on the broader interface, which is usually 10s of nm long. Fully simulating this interface with DFT is computationally prohibitive, and most studies simulate smaller portions. This reduction eliminates the information about the surrounding electric field, however, and thus the interaction with the global potential is unaccounted for. In this talk, we introduce the Quantum Continuum Approximation (QCA) as a methodology for including interface voltage information into limited-size DFT calculations by self-consistently coupling DFT calculations of defect/interface regions to Poisson-Boltzmann descriptions of the surrounding insulating and electrolyte regions. By reducing the number of atoms needed to incorporate voltage information into DFT calculations by an order of magnitude, QCA makes the voltage-dependent first-principles study of full electrochemical interfaces viable. We demonstrate this methodology to examine Cl- ion insertion into aluminum/aluminum oxide interfaces as a function of voltage. We find good agreement between the voltage threshold for stability predicted by QCA and those found experimentally. We then demonstrate QCA as a tool for measuring Li+ ion transport barriers through different solid-electrolyte interface (SEI) regions in battery chemistry as a function of voltage. Our work demonstrates the ability to attach a potentiostat to DFT calculations of interfaces relevant to simulations of electrochemical applications at reasonable computational cost.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525
(Invited) Using Molecular Dynamics Simulations to Relate Morphology to Water and Ion Dynamics in Hydrated Ion-Conducting Polymers
Authors: Frischknecht Amalie L.
Published: September 2023

Hydrated ion-containing polymer membranes are used as electrolytes in a variety of applications, including in fuel cells and in alkaline batteries. Achieving high conductivity in hydrated, ion-conducting polymers typically requires the hydrophobic backbone of the polymers to be nano-phase separated from the hydrophilic domains so that the ions (protons or hydroxide ions) have well-defined water domains for efficient transport. The ion transport thus depends strongly on the hydration level and on the detailed morphology of the hydrophilic domains. It is often difficult to determine the morphology of these domains experimentally. I will present results from atomistic molecular dynamics (MD) simulations that reveal the domain morphology in various ionic polymers. Increasing water content generally leads to an increase in the characteristic spacing between hydrophilic domains. However, this swelling can be obscured in X-ray scattering due to a loss of scattering contrast between the hydrophobic and hydrophilic domains. The MD simulations reveal that the systems are nano-phase separated, even when X-ray scattering appears to indicate otherwise. Calculated and measured scattering profiles are in good qualitative agreement. I will discuss several methods to characterize the water domain morphology in more detail, including various measures of pore size distributions, surface areas, and fractal dimension. Water and ion diffusivities calculated from the MD simulations follow the experimentally-measured trends in conductivity and are consistent with changes in the nanoscale morphology with changing water content. I will discuss the implications of the results for the future design of ion-conducting polymers for use as membranes in electrochemical devices.

This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE’s National Nuclear Security Administration under contract DE-NA-0003525.

Figure 1
Investigation of Electrocatalytic CO2 Reduction Reaction Mechanism: Role of H2s and Exsolved Metal Nanoparticle at Perovskite Oxides Electrodes
Authors: Aydogdu Irfan , Martinez Rios Franz Michel , Birss Viola Ingrid , Ponnurangam Sathish
Published: September 2023

ABSTRACT

Affordable and sustainable energy demands from post-modern society as well as the need to lower the CO2 emissions require alternative approaches rather than business-as-usual [1]. Solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) are one of the promising technologies that are being developed to meet these needs. The working principle of an SOEC is based on heterogeneous electrocatalysis to produce syngas (CO and H2) by splitting CO2 and H2O at high temperatures. The stability and electrochemical performance of the components, including the solid-state electrolyte and the electrode materials, are vital to making this technology mature enough to enhance its economic competitiveness [2]. Therefore, the physical and chemical features of the components need to be understood fundamentally. Due to its high electrocatalytic activity, Ni-YSZ cermets are still the most commonly used electrode materials in SOECs. However, the poisoning of these catalysts by sulfur deposition and coke formation is a problem. As a result, there has been growing interest in using mixed conducting perovskites oxides (MIECS) as electrode materials, which are more resistant to these challenges and as their chemical and physical properties can be easily tailored [3].

Here, we investigate a family of MIECS that can be used in many fuel environments and is also highly active in air, namely LCFCr (La0.3Ca0.7Fe0.7Cr0.3O3-δ). One specific objective of the current study is to elucidate the CO2 reduction mechanism based on varying the composition of LCFCr [4,5] as well as by alterations of the operating conditions, such as temperature, reactant gas mixture, and applied potential. Importantly, the effect of the presence of H2S in the gas phase [6] and ex-solved metal nanoparticles on the surface [7] during exposure to CO2 at open circuit and under CO2 reduction conditions is being investigated. This work involves the use of reactive molecular dynamics (ReaxFF MD), electrochemical perturbations, and thermo-catalytic methods, with our initial ReaxFF MD results showing good agreement with the experimental results [8].

ACKNOWLEDGMENTS

This computational research was supported by the Canada First Research Excellence Fund (CFREF), while the platforms for this computational work were provided by Westgrid (https://www.westgrid.ca) and Compute Canada (https://www.computecanada.ca). Thanks are also extended to Dr. Haris Ansari, Oliver Calderon, Michael Pidburtnyi, Dr. Scott Paulson, Dr. Anand Singh, Sara Bouzidi and Adam Bass for helpful discussions.
(Invited) Bridging the Gap between the Physics and Chemistry of Electric Double Layer
Authors: Wu Jianzhong
Published: September 2023

Classical models of electric double layer (EDL) are mostly concerned with ion distributions and their responses to the surface potential that can be regulated by changing either the voltage or the extent of surface ionization. With the help of adjustable parameters, classical EDL models are able to describe diverse physical phenomena including EDL capacitance and ion transport in good agreement with experimental measurements. However, major challenges remain in understanding chemical reactions within EDL important for the rational design and optimization of electrochemical processes such as energy storage and electrocatalysis. In this talk, I will present a molecular-thermodynamic model to predict the charging behavior of ionizable surfaces under various solution conditions. If a solid is non-conductive, the surface reactions can be reliably described with a Langmuir-type model coupled with liquid-state methods to account for the local thermodynamic non-ideality. When a solid is conductive, however, the electronic properties of different surface sites are intrinsically coupled with each other leading to highly correlated surface reactions. While the brute-force prediction of chemical equilibrium at an electrified surface is computationally prohibitive, a combination of the first-principles calculations and coarse-grained modeling provides complemental information that may be useful for diverse electrochemical applications.
A Diffuse-Interface Description of Electron Tunneling across Solid Electrolyte Interphases
Authors: Ji Yanzhou , Nabavizadeh Seyed Amin , Wu Qisheng , Qi Yue , Chen Long-Qing
Published: September 2023

Solid electrolyte interphase (SEI) is an electronically insulating layer on battery electrode due to electrolyte decomposition, which critically affects the battery performance. Electron tunneling is a key short-term electron transport mechanism that controls the SEI thickness and its growth behavior. The electron tunneling behavior is governed by the static Schrödinger equation and the tunneling barrier of SEIs, which shows an exponential decay of electron probability across the SEI layer. Here we develop a diffuse-interface description of electron tunneling behavior by formulating a phase-dependent tunneling barrier, so that the electrode/SEI and SEI/electrolyte interface positions do not need to be explicitly tracked when numerically solving the Schrödinger equation. We will show that this diffuse-interface description can accurately and efficiently predict the electron tunneling behaviors in 2D and 3D especially when the electrode/SEI and SEI/electrolyte interfaces are highly nonuniform. Furthermore, we will show that it can be seamlessly integrated with the phase-field simulation of electrodeposition and SEI growth in lithium-ion batteries, providing guidance for controlling the SEI morphology and improving the battery performance.
Elucidating the Performance Limits for Electrochemical CO2 Separation Using Exergy Loss Analysis and Zero-Dimensional Modeling
Authors: Ali Fawaz , Modak Sanat Vibhas , Kwabi David G.
Published: September 2023

The use of renewable electricity to power electrochemical CO2 removal and concentration from point sources, air, and seawater is receiving considerable interest as one strategy in our portfolio of options for mitigating climate change. Two common embodiments of this idea involve CO2 separation via electrochemically reversible binding of CO2 to a nucleophilic redox mediator, or a pH swing/gradient in aqueous solution. For either embodiment to be feasible, the energetic cost of regenerating the sorbent should be low at practical separation throughputs. Consequently, there have been a number of efforts to understand how the thermodynamic minimum work input for a given separation cycle varies under different conditions using modeling. In this talk, we demonstrate that the thermodynamic minimum work input for electrochemical CO2 separation is the sum of exergy losses incurred from differences between the partial pressure of CO2 within the CO2 source/exit streams and the partial pressure of CO2 in the sorbent. This framework rationalizes minimum work inputs for pH-swing and redox-mediator-based CO2 separation cycles, and motivates the measurement or estimation of the aforementioned CO2 partial pressures in experimental studies. Applying a zero-dimensional model recently developed in our group to pH-swing-driven CO2 separation, we will then discuss how the total energetic cost of CO2 separation can be simulated under a variety of scenarios relevant to practical CO2 concentration from flue gas.
(Invited) Graphene-Capped Micro-Reactors for X-Ray Photoelectron Spectroscopy Measurements Under Electrochemical Control
Authors: Eren Baran
Published: September 2023

A micro-electrochemical cell is sealed with 2–5 layers of graphene to monitor the changing oxidation state of Cu and Ni nanoparticles (NPs) with X-ray photoelectron spectroscopy (XPS) in a mildly alkaline aqueous solution under electrochemical control. The main role of graphene is to ensure an abrupt change between the liquid and vacuum environments, where the latter is required for conducting XPS experiments. Decent transparency to the generated photoelectrons with a kinetic energy of few hundred eV is another requirement that graphene fulfills for performing such experiments. Graphene also acts as an electrically conducting support material for Cu and Ni NPs, ensuring that a bias can be applied to them. Proof-of-concept measurements will be presented in this talk, which show that relatively lower flux X-ray sources, such as those with Al-Kα emission that are commonly used in laboratories, are sufficient for probing the electrified solid–liquid interfaces with this approach.
Cu Surface Chemistry in Acid Media: Vibrational Spectroscopy, Mass Spectrometry and ECSTM Measurements
Authors: Raciti David , Hight Walker Angela , Moffat Thomas P
Published: September 2023

Copper electrodeposition is a central process in the metallization of microelectronics and more recently copper has also found use as an important electrocatalyst in the conversion of CO2 to hydrocarbons. Gaining mechanistic insight into the reactivity of Cu surfaces requires in situ and better still in operando measurements. Herein the utility of the combination of vibrational spectroscopy (SEIRAS, SHINERS), electrochemical mass spectrometry (EC-MS) and scanning tunneling microscopy (ECSTM) to examine the competitive and co-adsorption interactions between potential dependent halide adsorption, molecular adsorption, underpotential metal deposition and hydride formation on low index Cu single crystals surface will be detailed. Further still, the emergent opportunity to study the impact of such interaction on metal deposition reactions will also be explored.

1.Raciti and T.P. Moffat, “Quantification of Hydride Coverage on Cu(111) by Electrochemical Mass Spectrometry,” J. Phys. Chem., 126, 18734-18743 (2022).

2.Raciti, A.R. Hight Walker, T. P. Moffat, “Mapping Surface Chemistry During Superfilling with Shell- Isolated Nanoparticle Enhanced Raman Spectroscopy and X-ray Photoelectron Spectroscopy,” J. Electrochem. Soc., 169, 082506 (2022).

3.B.M. Tackett, D. Raciti, A.R. Hight Walker, T.P. Moffat, “Surface Hydride Formation on Cu (111) and its Decomposition to Form H2 in Acid Electrolytes,” J. Phys. Chem. Lett., 12, 10936-10941 (2021).

4. G.Liu, S. Zou, D. Josell, L.J. Richter and T.P. Moffat, “SEIRAS Study of Chloride Mediated Polyether Adsorption on Cu,” J. Phys. Chem. C., 122, 21933-21951, (2018).
(Invited) Towards a Mechanistic Understanding of the Oxygen Evolution Reaction on Hematite: Operando Characterization of Band Bending and Interfacial Chemical Speciation Using Sum Frequency Generation Spectroscopy
Authors: Yang Yuke , Tong Yujin , Campen R. Kramer
Published: September 2023

Hematite is an attractive photoanode for the oxygen evolution reaction (OER) due to its cheap price, relatively small band gap, stability in alkaline solution and a valence band energy suitable for OER catalysis. However, insight into the OER mechanism, and thus the capability to rationally modify this material to optimize performance, is limited by the challenge in relating band bending, surface state population and chemical reactivity operando. Conventionally these issues are addressed by some combination of electrochemical impedance spectroscopy (EIS), photocurrent/voltage kinetics, and linear optical spectroscopies in the visible. While important, all of these approaches suffer from significant limitations: e.g. EIS and related techniques integrate over all charge transfer processes in the device while only those at the hematite/water interface are of interest (and thus require a challenging to validate model to quantify) and UV/Vis absorption measurements (whether steady-state or time resolved) are bulk-sensitive and probe spectrally broad features that are challenging to relate to surface structure.

Sum Frequency Generation (SFG) spectroscopy is interface-specific by its symmetry selection rules, can straightforwardly probe interfacial chemical speciation if one of the two incident fields is in the infrared, and is sensitive to the amplitude of interfacial electric fields. These attributes make the technique particularly suitable for characterization of interfacial chemical speciation, double layer and space charge layer structure at the working electrode/electrolyte interface within thin-film spectroelectrochemical cells. Here I describe our recent efforts to characterize chemical speciation and interfacial field at a hematite/electrolyte interface, in the presence and absence of external illumination, as one moves from the Hematite flat band potential through the onset of the OER. Using vibrationally resonant SFG spectroscopy, at infrared wavelengths > 10 micron, we quantify the population of surface holes, i.e. Fe(IV)=0 groups, as the OER turns on. Concurrently we quantify the development of the space charge potential using non-resonant SFG. Recent work has argued, largely from current or optical transients in the visible under chopped illumination, that the OER on Hematite proceeds by a multi-hole mechanism. Because our approach allows for the simultaneous quantification of interfacial field and chemical speciation we directly address this mechanism and the circumstances under which it is expected to apply. More generally, the role of interfacial field in oxidation catalysis has been an object of much current interest. The approach described here – in which interfacial speciation and field can be quantified operando – offers an ability to explore this relationship not possible via any other combination of experimental approaches.
The Role of Imidazolium 2-Cyanopyrrolide Ionic Liquid in Reduction of CO2 to CO, Formate, and Ethylene on Copper Electrode Revealed By SERS
Authors: Coskun Oguz Kagan , Dongare Saudagar , Klemm Aidan , Gurkan Burcu E
Published: September 2023

Electrochemical conversion of CO2 over copper catalyst is known to produce higher value products such as methane, ethylene, formate and alcohols in aqueous electrolytes. Since CO2 is a stable molecule, the electrochemical reduction reaction requires significant overpotential (-1.9 V vs SHE) for the first electron transfer to form CO2
-. Ionic liquids (ILs) have high CO2 solubility and can be further functionalized to bind with CO2 such that CO2 can be brought to the electrode surface in a more reactive state. In this study, we studied electroreduction of CO2 over copper in non-aqueous electrolyte with the reactive IL 1-ethyl-3-methylimidazolium 2-cyanopyrolide ([EMIM][2-CNpyr]) in the concentration range of 0.1 to 1 M. The linear sweep voltammetry experiments show the absence of a noticeable Faradic current within the potential window of -1.8 to -2.2 V vs Ag/Ag+ under N2 demonstrating the stability of the imidazolium cation against electrochemical conversion, which is also confirmed by NMR analysis. In the presence of CO2, the onset potential of reduction is at -1.9 V vs Ag/Ag+ (-1.4 V vs. SHE) and does not change with IL concentration. By employing surface enhanced Raman spectroscopy (SERS), potential dependent changes in the interfacial microenvironment during CO2 reduction was revealed. Specifically, imidazolium enrichment and surface adsorbed CO formation were captured. These results confirmed the catalytic role of the IL by facilitating the transport of the reactive CO2 to the electrode surface via imidazolium in particular. On the other hand, surface coverage by imidazolium cations on the electrode seems to prohibit higher level of C-C couplings, thus limiting reaction products to C1 and C2 products. During 3 hrs of bulk electrolysis at -2.1 V (vs. Ag/Ag+) in an H-cell with non-aqueous negolyte containing the IL and an aqueous posolyte (proton source), gaseous products of CO and H2, liquid product of HCOO- and dissolved C2H4were determined by GC and NMR analysis, respectively. Oxidation of Cu electrode was separately captured by ex-situ XPS measurements after 3 hrs of bulk electrolysis. Even though high CO2 concentrations are achieved in ILs and they are stable at CO2 reduction conditions even after 3 hours on Cu surface, IL structure should be optimized to allow C-C coupling to obtain C2+ products.
Spectroelectrochemical Detection of Acetaldehyde in Wines
Authors: Williams Kia , Ibáñez David , González-García María Begoña , Hernández-Santos David , Fanjul Pablo
Published: September 2023

The combination of electrochemical sensors and spectroscopy has been scarcely used due to the traditional instrumental limitations of spectroelectrochemical techniques. However, the development of new setups and commercial instruments enables the spectroelectrochemical detection of a variety of analytes [1]. In that way, UV-Vis spectroelectrochemistry joins the advantages of electrochemistry and UV-Vis spectroscopy, improving the analytical features that both techniques have separately.

In this work, a new spectroelectrochemical two-enzyme sensor system has been developed for the detection of acetaldehyde in wine. Spectroelectrochemical detection is achieved by the analysis of the optical properties of the ferri/ferrocyanide redox couple involved in the enzymatic process: aldehyde dehydrogenase catalyzes the aldehyde oxidation using NAD+ as a cofactor and, simultaneously, diaphorase reoxidizes the NADH formed in the first enzymatic process due to the presence of ferricyanide. The analysis of the characteristic UV-Vis bands of ferricyanide at 310 and 420 nm allows the detection of acetaldehyde, since absorption bands are only related to the oxidation of this substrate and avoids the contribution of other interferents [2]. Two different wines have been evaluated in this work, obtaining excellent results that agree with the literature as well as with those obtained with a commercial fluorogenic kit.

References

[1] C. Navarro, M.B. González-García; D. Hernández-Santos; M.A. Heras, A. Colina, P. Fanjul-Bolado, Electrochem. Commun. 2016, 64, 65–68.

[2] D. Ibáñez, M. B. González-García, D. Hernández-Santos, P. Fanjul-Bolado, Biosensors 2022, 12, 1032.
Using Ambient Pressure Photoelectron Spectroscopy to Investigate the Time Dependence of Electrostatic Potential Difference over the Interphase between an Electrode and an Electrolyte
Authors: Krizan Alenka , Ericson Tove , Kallquist Ida , Chen Heyin , Temperton Robert , Dominko Robert , Gaberscek Miran , Hahlin Maria
Published: September 2023

Ambient pressure photoelectron spectroscopy (APPES) is a method well-suited for measuring the change ∆φ in electrostatic potential difference φ over an interphase between an electronic conductor and an insulator. APPES had previously been used to compare ∆φ over an interphase between an electrode and an electrolyte with the change in electrochemical potential difference ∆UWE-RE
between the working and the reference electrode UWE-RE
.[1] The relationship between ∆φ and ∆UWE-RE
at low current-transient had been shown to follow two distinct trends depending on whether charge transfer of Li+ ions between an electrode and an electrolyte occurs or not.[1,2] In this work, APPES was used to investigate the time dependence of ∆φ after changing UWE-RE
. The studied electrochemical system consisted of Au (working electrode), Li4Ti5O12 (reference electrode) and a second Li4Ti5O12 (counter electrode) with 0.008 M LiClO4 in propylene carbonate (PC) as the electrolyte. Pressure in the sample compartment was equal to the saturated PC pressure. APPES experiments were performed at HIPPIE beamline at MAX IV in Lund and were conducted as follows. After applying a potential step ∆UWE-RE
, a C 1s spectrum was measured every 7 s. Incident photon energy was 1800 eV. Each spectrum was fitted using a Python code written especially for the obtained C 1s spectra. Time dependence of ∆φ was extracted from the shift in the kinetic energy ∆KE of the C=O peak (∆φ = ∆KE). Experiments were performed in both regimes, i.e. when the working electrode behaves as an ideal polarizable electrode and when it behaves as an ideal non-polarizable electrode, and have shown the time dependence of ∆φ to differ for the two regimes. Behaviour of ∆φ(t) as well as the experimental setup and spectral fitting using the Python code will be discussed.

Figure 1: a) Schematic depiction of the electronic electrostatic potential φ between a working (WE) and a reference electrode (RE). Electrostatic potential profile is not to scale. b) An example of the experimentally obtained time dependence of the C=O peak kinetic energy KE(t). KE(t) is related to φ(t) as ∆φ(t) = ∆KE(t).

References:

[1] Källquist, I. et al. Probing Electrochemical Potential Differences over the Solid/Liquid Interface in Li-Ion Battery Model Systems. ACS applied materials & interfaces
13, 32989–32996 (2021).

[2] Källquist, I. et al. Potentials in Li-Ion Batteries Probed by Operando Ambient Pressure Photoelectron Spectroscopy. ACS Applied Materials & Interfaces
14, 6465-6475 (2021).

Figure 1
(Invited) Using Synchrotron Techniques to Pry into Lithium-Ion Batteries Limitations
Authors: Mauzeroll Janine , Schougaard Steen Brian
Published: September 2023

Li-ion batteries have been highly successful since they were introduced commercially some 30 years ago. However, there are still improvement to be made to reduce cost, charging times, energy density etc. In this talk, we will present the some of our recent synchrotron radiation-based work on the sub-processes that must work in unison for lithium battery operation, in particular at high current densities. Specifically, we will present work at the particle level on high power charging, illustrating how under favorable conditions some commercial cathode materials may be fully charged within tens of seconds. Moving towards the electrode scale, our latest technique development include an x-ray fluorescence technique that permits the determination of the electrolyte concentration within
the electrode during battery operation. As such, this represent a major step forward towards validating mesoscale modeling as well as testing novel electrode architectures specifically designed for improved electrolyte transport. The importance of the electrode design is that in theory it can provide higher active material loading per area without losss of power capabilities. As such, the mass and volume of separator as well as current collector could be minimized improving both energy density and cost.
Improving Fast Charging Capability of Graphite Anode Material Via Si/SiO
x
Coating for Lithium-Ion Battery
Authors: Ma Donghyeok , Yu Mi , Kim Hansu
Published: September 2023

As the electric vehicle(EV) market is expanded, Lithium-ion batteries(LIBs) have faced a new challenge of fast charging. However, currently used graphite have limitation with poor kinetics and Li plating during fast charging process. To overcome this limitation, many materials have been researched for alternative of graphite materials. In this work, we propose Si/SiO
x
coated graphite material to improve fast charging capability and prevent Li plating. At a rate of 10 C-rate (3600 mA g-1), Si/SiO
x
coated graphite anode electrode exhibited 80.9 % of capacity obtained at a rate of 0.1 C-rate (36 mA g-1). Also, the Si/SiO
x
coated graphite is confirmed through the OCV behavior that Li plating is controlled. Therefore, surface modification by coating Si/SiO
x
on graphite anode material would be noticeable method to develop an anode material with fast charging ability for LIB. Detailed characteristic that material properties and electrochemical performance of Si/SiO
x
coated graphite will be discussed in the presentation.
Impact of Coin Cell Preparation and Testing Protocols on Coulombic Efficiency Measurements
Authors: Jiang Kyle S. , Gallant Betar M.
Published: September 2023

The lithium (Li) metal anode holds great promise for high energy-density rechargeable batteries due to its high gravimetric capacity (3860 mAh/g), an order of magnitude larger than graphite at a similar electrochemical potential (-3.040 V vs SHE for Li). However, limited Coulombic efficiency (CE), caused by the thermodynamic instability of conventional Li-ion electrolyte solvents and salts with Li that leads to unstable solid-electrolyte interphase (SEI) during repeated plating and stripping, has hindered the commercialization of Li metal batteries. Research efforts have focused on tuning the electrolyte composition to promote a stable SEI that simultaneously blocks continuous side reactions and electronic conductivity while facilitating Li+ transport [1], with coin cells being by far the most preferred form factor for evaluating these electrolyte designs.

Coin cells enable accessible and rapid testing of diverse electrolyte compositions. Their preparation requires no specialized equipment beyond an inert chemical environment, a crimping mechanism to seal the cell, and modest quantities of Li metal (~50 - 100 μm thickness) and electrolyte (~50 - 100 μL volume) [2]. Despite these attractive features, the procedures for preparing and techniques for measuring CE in coin cells are not fully standardized. In this presentation, we examine the impact on measured CE from preparation and testing procedures, including the internal coin cell stack consisting of components such as the electrodes, current collectors / spacers, and separators, and the cycling protocol. While the cycling protocol and cycling capacity are known to affect capacity loss mechanisms in Li metal batteries [3], we show that variances in CE can additionally be attributed to specific details of cell preparation. In particular, the working electrode area and stack thickness affect the pressure magnitude and uniformity inside the cell. We demonstrate that standardizing the procedures for preparing coin cells reduces variation due to nonuniformities and edge effects and hence improves the reproducibility of CE measurements.

[1] Hobold, G. M., et al. Nature Energy
2021
6 (10), 951-960.

[2] Xiao, J., et al. Nature Energy
2020
5 (8), 561-568.

[3] Adams, B. D., et al. Advanced Energy Materials
2018
8 (7), 1702097.

Figure 1
Prelithiated SiO
x
Anode Materials for Fast Chargeable Lithium-Ion Batteries
Authors: Yu Mi , Ma Donghyeok , Kim Hansu
Published: September 2023

To meet the increased demands for electric vehicles(EV), Lithium-ion batteries(LIBs) requires fast charging capability. Conventional LIBs using graphite anodes (with a theoretical specific capacity of 372mAh g-1) have limitations with lithium plating and slow kinetics during fast charging process. To overcome these limitations, many anode materials have been explored in the attempt to replace graphite. Among silicon based anode materials, SiO
x
is one of suitable materials for fast charging due to its high reaction voltage and high energy density. However, its low initial Coulombic efficiency(ICE) and poor cycle life remain as critical challenges. Herein, we propose prelithiated SiO
x
materials prepared by dehydrogenation-driven prelithiation of SiO
x
using LiH to improve the low ICE and poor cycle life. The prelithiated SiO
x
shows about 85.5 % of ICE and improved long-term cycle performance for over 300 cycles. Also, the prelithiated SiO
x
anode shows higher charged capacity at high current density. More detailed microstructure and electrochemical properties of the prelithiated SiO
x
materials will be discussed in this presentation.
Toward the Development of an Electrochemical Aptamer-Based Sensor for Preterm Birth Biomarker, Interleukin-6
Authors: Buckey Grace , Cliffel David E
Published: September 2023

Preterm birth (PTB) is the leading cause of death in newborns and children under the age of five. While certain cytokines, like interleukin-6 (IL-6) are known to facilitate the degradation of the fetal membrane, the mechanisms that result in fetal membrane rupture under both normal and pathological conditions are largely unknown. Electrochemical sensors for cytokines can provide further insight into the mechanisms underlying PTB by offering low-level protein biomarker quantification.Electrochemical aptamer-based (EAB) sensors afford advantages like rapid and sensitive detection, reagentlesssignaling, easy fabrication, and reusability. The aptamer is typically modified with a reversible electrochemical tag, methylene blue, to allow for electrochemical detection without addition of labeling reagents to the sample, a quality often referred to as reagentless, and with a C6-thiol to allow for ease of fabrication. However, the development of new aptamer-based sensors for clinically relevant targets faces several challenges that limit their widespread application. The primary challenge in the development of an IL-6 EAB sensor involves the absence of signal change upon aptamer–IL-6 binding, possibly due to an absence in conformational change. Current strategies to improve sensor performance include sensor interrogation via an in solution redox couple to remove the need of conformational change.
Electroanalytical Measurement of Steroid Hormone with Carbon Electrode Sensor
Authors: Zestos Alexander George , Hadad Michelle , Hadad Nadine
Published: September 2023

Cortisol is a vital steroid hormone that has been known as the “stress hormone,” which is elevated during times of high stress and anxiety. The improved detection of cortisol is critically important as it will help further our understanding of stress during several physiological states. Several methods exist to detect cortisol, however, they suffer from low biocompatibility, spatiotemporal resolution, and are relatively slow. In this study, we developed an assay to measure cortisol with carbon fiber microelectrodes (CFMEs) and fast-scan cyclic voltammetry (FSCV). FSCV is typically utilized to measure small molecule neurotransmitters by producing a readout CV for the specific detection of biomolecules on a fast, subsecond timescale with biocompatible CFMEs. It has seen enhanced utility in measuring peptides and other larger and more complex molecules. We developed a waveform to electro-reduce cortisol at the surface of CFMEs. The sensitivity of cortisol was found to be 5 nA/uM and was adsorption controlled on the surface of CFMEs and stable over several hours. Cortisol was co-detected with several other biomolecules such as dopamine and serotonin, and the waveform was fouling resistant to repeated injections of cortisol on the surface of the CFMEs. Furthermore, we also measured exogenously applied cortisol onto brain tissue and simulated urine to demonstrate biocompatibility and potential use in vivo. The specific biocompatible detection of cortisol with high spatiotemporal resolution will help further elucidate its biological significance and further understand its physiological importance in the brain.
High-Entropy Oxides as Nanozymes for Non-Immunological Electrochemical Monitoring of Cortisol
Authors: Yin Ziyu , Clark Kaylee , Ray Tyler R
Published: September 2023

High entropy oxides (HEOs) are a class of materials that have garnered significant attention in recent years due to their potential use as catalysts in energy-related applications[1]. These materials are derived from high entropy compounds, which consist of equimolar or near equimolar ratios of multiple primary elements and have configurational entropy in the formation of a single-phase structure. The cocktail effect of HEOs gives rise to various catalytically active sites due to the synergistic interaction of the different elements, and lattice distortion during the formation of a single-phase solid solution results in the generation of abundant oxygen vacancies, which enhances the adsorption activity of HEOs and improves their catalytic performance[2]. HEOs can also be cost-efficient by utilizing low-cost transition metal elements as their active centers. Despite their widespread use as catalysts, the application of HEOs in electrocatalysis for molecule monitoring and early diagnosis remains largely unexplored.

Cortisol, a glucocorticoid hormone that regulates many aspects of metabolism, stress, and immune response, is closely related to various diseases and disorders[3]. Current methods for noninvasive monitoring of cortisol relies upon immunological assays and typically limited to labor-intensive and time-consuming laboratory techniques. As a consequence, detecting cortisol in a label-free manner that is low cost and offers significant sensor stability and high sensitivity is desirable for many emerging applications, particularly for on-body monitoring.

Here, we present work that examines the catalytic activities of HEOs as nanozymes for the electrocatalysis of cortisol. The electrochemical cortisol sensor is based on a novel one-pot microwave-assisted reaction synthesized (Fe, Co, Mn, Ni, Cu) Ox. The catalytic mechanism of electrochemical sensors depends on the formation of various valence metal redox species pairs, where the higher valence state oxidizes cortisol species present on the electrode surface, accompanied by a reduced lower valence state. The one-pot microwave-assisted synthesized HEOs exhibited ultra-high catalytic activity towards cortisol species as measured by cyclic voltammetry and chronoamperometry. Experimental results show a superior sensing performance including a detection limit as low as 0.5 µM (s/N=3), a good linear detection range between 0.01 ~ 4.01 µM, and a sensitivity of 46.5 µA µM-1 cm-2.

References:

[1] Y. Pan, J.-X. Liu, T.-Z. Tu, W. Wang, and G.-J. Zhang, “High-entropy oxides for catalysis: a diamond in the rough,” Chem. Eng. J., p. 138659, 2022.

[2] D. Feng et al., “Holey lamellar high-entropy oxide as an ultra-high-activity heterogeneous catalyst for solvent-free aerobic oxidation of benzyl alcohol,” Angew. Chem., vol. 132, no. 44, pp. 19671–19677, 2020.

[3] B. Wang et al., “Wearable aptamer-field-effect transistor sensing system for noninvasive cortisol monitoring,” Sci. Adv., vol. 8, no. 1, p. eabk0967, 2022.