bluuebunny/crossref_metadata_2025 huggingface dataset:
Facilitated Enzymatic Chain Reaction-Based Bioelectrocatalysis via Solid Binding Peptide-Guided Bienzyme Co-Immobilization Strategy
Authors: Lee Hyeryeong , Bang Yuna , Chang In Seop
Published: September 2023

The multienzyme complex in biological systems are highly ordered so that intermediate molecules occurred during enzymatic sequential reaction are efficiently delivered to downstream enzymes without diffused to bulk phase. Recently, the cascadic multienzymes have been adopted to enzymatic electrocatalytic platform to be applied for enzyme-based bioelectronics such as enzyme fuel cell, biosensors, and electrosynthetic system. This cascadic enzyme-electrode, in which interfacial electron transfer (ET) occurs concurrently with inter-enzyme chain reaction, has been regarded promising for the advancement of enzyme-based bioelectronics performance. However, co-regulation of interfacial electrical connection and inter-enzyme chain reaction efficiency has been known to be highly challenging due to systematic complexity. In this context, the generalized enzyme immobilization tool is significantly needed to be developed to control inter-enzyme and enzyme-electrode interface concurrently.

Herein, enzyme cascade-based direct bioelectrocatalytic system has been constructed by immobilizing enzymes using the solid binding peptide (SBP) linker that can control surface-orientation of enzymes on electrode. Here, invertase (INV) and FAD-dependent glucose dehydrogenase gamma-alpha complex (GDHγα) were utilized as upstream- and downstream enzyme so that the sucrose hydrolysis (at INV) and glucose oxidation (at GDHγα) is concomitantly occurred. Especially, the GDHγα that is direct electron transfer (DET)-capable oxidoreductase, has bi-function that are downstream catalysis and transport of produced electrons toward electrode that cause bioelectrocatalytic current signal. To immobilize enzymes and control relative orientation of coupling enzymes, the SBP linker was tethered various termini (C-, N-, or both termini) of INV when SBP fusion site of GDHγα was fixed to C-terminus of GDH α subunit to enable efficient interfacial DET, based on previous study. Therefore, the inter-enzyme relative orientation dependent chain reaction efficiency was evaluated with resulting DET-based electrocatalytic current. In the result, it was found that the interfacial DET at GDHγα-electrode could be affected by binding conformation of co-immobilized enzyme, fusion INV. Most importantly, the chain reaction efficiency between INV and GDHγα was revealed to be diverse depending on different relative orientation determined by SBP tethering sites in enzymes. The intermediate delivery route was changed by relative positioning of coupling active sites, affecting overall cascade reaction rate. Taking into account the factors related with interfacial DET and intermediate delivery, precise design of bienzymatic electrode is indeed necessary in order to introduce SBP-tethering technique to cascadic enzyme-derived direct electrocatalytic platform.

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Colorimetric Assay for Protein Redox Activity – a Complement to Electrochemistry
Authors: Baskaran Barathkumar , Gill Thomas Mark , Furst Ariel L
Published: September 2023

Oxidoreductases are vital biocatalytic tools for driving redox conversions that are challenging using conventional catalysts. Monooxygenases, an important class of these enzymes, have been the subject of enzyme engineering due to their high activity and versatile substrate scope. Reactions performed by these biocatalysts have long been monitored by a colorimetric method involving the coupling of a dye precursor to naphthalene hydroxylation products generated by the enzyme. Despite the popularity of this method, we found the dye product to be unstable, preventing quantitative readout. By incorporating an extraction step to solubilize the dye produced, we have improved this assay to the point where quantitation of enzyme activity is possible. Further, by incorporating spectral deconvolution, we have, for the first time, enabled independent quantification of the two possible regioisomeric products: 1-naphthol and 2-naphthol. Previously, such analysis was only possible with chromatographic separation, increasing the cost and complexity of analysis. The efficacy of our improved workflow was evaluated by monitoring the activity of a toluene-4-monooxygenase enzyme from Pseudomonas mendocina KR-1. Our colorimetric regioisomer quantification was found to be consistent with chromatographic analysis by HPLC. The development and validation of a quantitative colorimetric assay for monooxygenase activity that enables regioisomeric distinction and quantification represents a significant advance in analytical methods to monitor enzyme activity. By maintaining facile, low-cost, high-throughput readout while incorporating quantification, this assay represents an important alternative to more expensive chromatographic quantification techniques. For the electrochemistry community, the use of monooxygenases or other redox capable enzymes for biocatalysis must be complemented by a toolkit of methods for accurate enzyme activity measurement. Our approach demonstrates that accurate, mixture analysis is possible in a higher throughput using the improved colorimetric method. The relevant assay reaction, the hydroxylation of naphthalene, may be readily incorporated in the future for measurement schemes with other enzymes than the tested toluene-4-monooxygenase, thus enabling opportunities to tune these biocatalysts towards desired activities.
Polypyrrole Electrodes Show Strain-Specific Enhancement of Photocurrent from Cyanobacteria
Authors: Roullier Charlotte , Reggente Melania , Gilibert Pierrick , Boghossian Ardemis Anoush
Published: September 2023

Except for a limited number of exoelectrogens, most microbes of interest are surrounded by insulating membranes impairing an efficient extracellular electron transfer. This study focuses on the fabrication of a conductive polypyrrole (PPy) based coating for enhancing microbial charge extraction. The polymer deposition was characterized and optimized using a combination of potentiodynamic and potentiostatic measurements as well as scanning electron microscopy (SEM), energy dispersive X-Ray (EDX) analysis, and Raman spectroscopy. The electrodes were used to extract photosynthetic electrons from the cyanobacteria Synechocystis sp. PCC6803 and Synechococcus Elongatus PCC7942. The PPy electrode showed a six-fold increase in extracted photocurrent for Synechocystis under unmediated conditions compared to bare graphite electrodes. This enhancement was attributed to decreased resistivity and increased electroactive surface area of the PPy electrode. By contrast, Elongatus showed no substantial difference in photocurrent between the PPy and bare electrodes. A comparison of the zeta potential and adherence of the cells suggested more limited charge interaction of Elongatus cells with the PPy surface compared to the Synechocystis cells indicating a strain-specific enhancement of these electrodes.
Construction of Solid Binding Peptide (SBP)-Fused Non-Native Chimeric Enzyme to Promote Bienzymatic Cascade Induced Bioelectrocatalysis
Authors: Bang Yuna , Lee Hyeryeong , Chang In Seop
Published: September 2023

In nature, most enzymes form a multienzyme complex called “metabolon” in the cellular system. The natural metabolon has been evolved to increase the efficiency of multi-step biocatalysis involved in such conditions. Such principle of enzymatic cascade reaction could be applied to the system which mimics pertinent reaction in vitro. Especially, its pertaining to bioelectrocatalytic system is quite promising to enhance its performance in terms of electrical generation or biochemical production, depending on systematic applications. In the previous studies , it was abundantly reported that multi-enzymatic reaction has been utilized to generate higher electrical current via sequential enzymatic oxidation of substrates (e.g., methanol, glucose, etc.) in bioelectrochemical systems, and to operate biochemical production system utilizing multi-enzymic conversion or reduction reactions. However, it is still challenging to implement multi-step enzymatic reaction in the electrode platforms due to unmanageable regulations of inter-enzyme distance or electrical connection between enzymatic cofactor and electrode, during multi-enzyme co-immobilization on electrode surface.

Herein, we intentionally design and construct variants of chimeric enzyme in which two enzymes, invertase (INV) and glucose dehydrogenase (GDH), are conjugated with peptide linkers. We expected that INV hydrolyzes sucrose into fructose and glucose, then glucose is oxidized at the catalytic subunit of GDH, releasing electrons toward the electrode. It also employed solid binding peptides (SBPs) fused to GDH in chimeric enzyme for the electrical connection of GDH-SBP and electrode. In order to accomplish the desired reaction with chimeric enzyme, we have conducted the following tests; 1) The recombinant plasmid harboring the genetic sequence of two enzymes with an in-between linker was constructed. 2) By production of chimeric proteins, the chain reaction efficiency of fusion constructs was compared depending on the length of the linker. 3) The gold binding peptide (GBP) was fused to sites (N- and C-terminus, or other sites) of the catalytic subunit of GDH. And finally, 4) the electron transfer rates were monitored and compared depending on the GBP tethering sites. Throughout the whole study, we found the factors affecting the occurrence of multienzyme cascade-based bioelectrochemical reactions and how to control these factors to improve the reaction efficiency

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Expanding Our Cyclodextrin-Based Sensors with Automation and New Surfaces
Authors: Sajedi Ferdows , Edgar Julia , Halpern Jeffrey M
Published: September 2023

We have had significant success in building cyclodextrin mediated sensors. We initially started with a gold surface, being able to detect analyte up to three times post modification [1]. Afterwards, we improved the stability and reusability by moving to a phenyl-modified carbon electrode via diazonium salt chemistry [2]. With his new surface, we were able to detect cortisol up to 10 different times with high accuracy, repeatability, and sensitivity in buffer, urine, and artificial saliva. We were limited by manually manipulating the electrode; therefore, we were not able to test the electrode for greater than 10 measurements. Within this poster, we intend to present our ideas and progress towards developing an automated detection system that can be preprogrammed to clean, reset, and test the cyclodextrin-mediated surface with target analytes. Further, we will share our various target analytes and our strategy to expand our sensor surface to include multiple cyclodextrin derivatives.

Research supported by New Hampshire- INBRE through an Institutional Development Award (IDeA), P20GM103506, from the National Institute of General Medical Sciences of the NIH.

[1] Z. Panahi, M. A. Merrill, and J. M. Halpern, “Reusable Cyclodextrin-Based Electrochemical Platform for Detection of trans -Resveratrol,” ACS Appl. Polym. Mater., vol. 2, no. 11, pp. 5086–5093, Nov. 2020.

[2] Z. Panahi, T. Ren, and J. M. Halpern, “Nanostructured Cyclodextrin-Mediated Surface for Capacitive Determination of Cortisol in Multiple Biofluids,” ACS Appl. Mater. Interfaces, Aug. 2022.
Electrodeposition of Ni-Co Alloys from Ionic Liquids and Their Electrocatalytic Properties
Authors: Turmine Mireille , Xie Yuelin , Miche Antoine , Vivier Vincent
Published: September 2023

Amorphous and nanocrystalline Ni-Co alloys have been deposited on FTO glass in ethylammonium nitrate (EAN), a protic ionic liquid (PIL). In a first step, the physicochemical properties of EAN with Ni2+ and Co2+ salts have been studied as well as the electrochemical behavior of these metal cations in the PIL in order to optimize the electroplating process (Fig. 1). It was shown that when the electrodeposition of Co, Ni and Ni-Co alloys was performed on FTO glass in EAN at 60 ℃ in an oxygen-free environment, nanocrystalline Ni-Co alloys with different atomic ratios were obtained, depending on both the deposition potential and the ion concentration in solution.

The electrocatalytic properties of these materials were then investigated towards the hydrogen evolution reaction (HER). It was shown that the addition of Co in Ni-based alloys can promote the HER, and most notably, amorphous Ni-Co alloys show lower overpotential or reaction rate. This work provides a new route to prepare nanocrystalline and amorphous Ni-Co alloys with different ratio in PIL for practical applications in electrocatalysis such as water splitting.

Figure 1
Assessing Proton and Hydrogen Permeabilities for Nanoscopic Oxide Coatings Using a Rotating Disk Electrode
Authors: Yim Kyungmin , Cohen Lucas , Fraga Alvarez Daniela V. , Jin Jingjing , West Alan C. , Weimer Matthew S , Dameron Arrelaine A , Moulton Staci , Fortiner Serafina , Glenn Jennifer , Hawkes Justin , Capuano Christopher , Ayers Katherine E. , Esposito Daniel V.
Published: September 2023

The transport of protons and molecular hydrogen (H2) are of relevance to a wide range of electrochemical applications ranging from fuel cells and electrolyzers to sensors and photoelectrochemical cells. One way to modulate the flux of these species to improve device performance such as selectivity and efficiency is to encapsulate electrodes with semi-permeable oxide coatings. [1-3] Thus, knowing the permeabilities of these species within thin oxide layers is of great importance for guiding the design of electrodes and devices. Towards this end, we have employed a modified rotating disk electrode (RDE) set-up to quantify proton and hydrogen permeabilities through sub- 20 nm thick silicon oxide coatings and understand how these transport properties change as a function of the structural and compositional characteristics of the coatings. Oxide coatings were fabricated by both atomic layer deposition (ALD) and photochemical deposition, and their physical and chemical properties characterized by X-Ray Photoelectron spectroscopy and ellipsometry. Based on measurements of the mass transfer limited current density for the hydrogen evolution and hydrogen oxidation reactions, permeabilities were computed. Species permeabilities are furthermore correlated with membrane density and composition, revealing structure-property-performance relationships that can be used to guide the selection of oxide thickness and processing conditions that will optimize performance for an application of interest.

References:

[1] Labrador, N. Y., et al. Hydrogen evolution at the buried interface between Pt thin films and silicon oxide nanomembranes. ACS Catalysis 8, 1767-1778 (2018).

[2] Beatty, M. E., Gillette, E. I., Haley, A. T. & Esposito, D. V. Controlling the Relative Fluxes of Protons and Oxygen to Electrocatalytic Buried Interfaces with Tunable Silicon Oxide Overlayers. ACS Applied Energy Materials 3, 12338-12350 (2020).

[3] Bhardwaj, A. A., et al. Ultrathin silicon oxide overlayers enable selective oxygen evolution from acidic and unbuffered pH-neutral seawater. ACS Catalysis 11, 1316-1330 (2021).
Paper-Derived Carbon Electrodes, a Versatile Option to Develop Electrochemical Sensors
Authors: Elashkar Nourhan Esmat , Ayres Lucas B , Vidal Ezequiel , Arroyo Netz , Garcia Carlos D
Published: September 2023

Carbon-based materials are particularly well-suited for electroanalytical applications due to their distinct properties, such as high chemical stability, large electroactive areas, wide electrochemical potential window in aqueous solutions, low electrical resistance, rich surface chemistry, and activity towards a variety of redox reactions. While carbon electrodes can be produced via thermal decomposition of gaseous hydrocarbons followed by their surface-induced recombination, this method is not cost-effective and suffers from both low efficiency (~20%) and limited selectivity towards graphitic forms. Alternatively, carbon electrodes can be developed via pyrolytic treatment of non-volatile substrates. This approach yields carbon materials that are rich in graphitic phases and provides researchers a much richer selection of starting materials and source-to-product efficiencies ~70%. Our team has applied this approach to develop several optically transparent carbon electrodes and has described a method for fabricating carbon electrodes by pyrolysis of paper, using a tube furnace and under a mild reducing atmosphere. The resulting electrodes not only feature the properties of traditional carbon materials but also preserve the 3D structure of the starting material, are mildly hydrophobic, and offer a wide electrochemical window and can be patterned using laser engraving. Moreover, the process also enables the incorporation of metallic nanoparticles within the structure of the material (by pyrolyzing paper pre-soaked in a solution containing the selected cation), significantly improving the conductivity of the material. Thus, this presentation will provide a brief summary of the reactions leading to the fabrication of these substrates as well as discuss the most recent applications towards their use as sensors in microfluidic devices.

Special emphasis will be placed on the use of these electrodes for the detection of S. aureus, application that required the modification of the material with a thin layer of sputtered gold (that minimizes lateral resistivity and significantly improves the electron transfer process) and with chitosan (used as a binder to offer flexibility). This biosensor was controlled using a custom-built potentiostat (via a wireless connection), which was used to detect the presence of the bacteria via the oxidation of the ferrocyanide (produced by the bacteria’s respiration cycle) in the presence of mannitol.

More information about the group can be found in our web site scienceweb.clemson.edu/uacl/
Applying Super High Resolution Fluorescence Microscope and Advanced Smart Cloud Algorithm in Real-Time Quantitative Processing and Analysis of Electroconvection
Authors: Zhang Duhan
Published: September 2023

In an electrochemical cell at high current densities, electroconvection plays a critical role in determining the morphology of electrodeposited metals. The resultant dendrite formation leads to risky battery performance failure. Over the past decades, though intensive theoretical analysis and experimental effort have been done, the detailed structure and dynamics of electroconvection remain unknown, because experimental observations lacked the resolution to expose the fundamental, hierarchical spatial structure of these flows, while the data processing algorithms were not fully established for large sample size. To address this shortcoming, we built an advanced optical electrochemical cell that fits in situ imaging with a super-resolution fluorescence microscope. By observing and recording real-time motions of electrolytes, electroconvection flows have been interrogated at unprecedented, high temporal and spatial resolution. As a complement to the visualization studies, a cloud-computing analysis algorithm was developed by combining a higher resolution Particle Image Velocimetry algorithm and a machine learning model to enable velocity distribution data over the entire optical field of view at nanoscale or microscale spatial resolution. Consequently, detailed velocity maps are obtained across the optical electrochemical cell, allowing us to quantitatively measure and analyze the initiation and evolution of the hierarchical microstructures inside the electroconvection in a unidirectional electric field. With these powerful tools, we further studied the effect of polymer viscoelasticity on electroconvection and electrodeposition. The addition of an ultrahigh molar mass polyethylene oxide to the electrolytes transforms the materials to a viscoelastic fluid state that changes the electroconvection dependence on time and voltage and induces a smooth electrodeposition on the metal anode by unique polymer rheological properties. Especially, the relaxation of long polymer chains in electrolyte provides a promising manner to prevent dendrite growth. We further analyzed these observations using direct numerical simulations for Newtonian and viscoelastic fluid models, and the quantitative analysis of experimental results indicates good consistency with simulation predictions.
Spatiotemporal Pattern Formation of Metal Electrodissolution Reactions Using Multielectrode Arrays in Lab-on-Chip Cells
Authors: Kiss Istvan Z , Tetteh John Anum
Published: September 2023

Electrochemical reactions can generate complex spatiotemporal patterns due to the inherent nonlinearities in the reaction kinetics, which often couple with various mass transfer and electrical coupling effects. We explore spatiotemporal pattern formation using multielectrode arrays embedded in flow channels. The kinetic equations are expressed as a superposition of local kinetics with a network of electrical coupling due to ohmic potential drops in the electrolyte. The networks are revealed by analysis of the synchronization patterns with the use of an oscillatory chemical reaction (nickel electrodissolution) and are further confirmed by direct decoding using phase model analysis. In dual electrode configuration, a variety coupling schemes, (uni- or bidirectional positive or negative) were identified depending on the relative placement of the reference and counter electrodes (e.g., placed at the same or the opposite ends of the ow channel). The synchronization patterns and the network configuration are compared for the linear and the branched channel configurations. With straight channel and multiple electrodes, a scale-free network was formed. With branched channels, the global to local coupling can be changed by the position of electrodes in the channel, and introduction of different concentration of electrolyte can mediate coupling between only the downstream electrodes. In fluidic network with cross channels, nonlinearity can be induced by obstacles in the channel which open ways to investigate the Braess’s paradox. The networked, electrode potential (current) spike generating electrochemical reactions hold potential for construction of an in-situ information processing unit to be used in electrochemical devices in sensors and batteries.
Mechanistic Study of Lithium Electrodeposition Using Dynamic Electrochemical Impedance Spectroscopy
Authors: Sacci Robert L , Sahore Ritu , Westover Andrew S
Published: September 2023

Lithium metal batteries have increased energy density over standard graphite-based Li-ion anodes. However, Li metal anodes have difficulty forming stable passivation layer (called solid electrolyte interphase, SEI) leading to poor use of Li inventory. That is, LI metals require larger cathode loading, which reduces the energy density gain. A holistic approach to Li anode incorporation includes electrolyte design, mechanism understanding, and battery engineering. A factor that has not been fully appreciated is the nature of the Lithium metal itself, namely its SEI before incorporation into the battery device may affect the subsequent SEI formation. Here, we present a mechanistic study on lithium SEI formation on various lithium sources, as well as the Li cycling.

We utilized dynamic impedance spectroscopy (dEIS) to probe the formation and evolution of the SEI during Li cycling of various Li sources. dEIS superimposes a multisine waveform atop the dc stimulus signal. After applying a sliding window FFT protocol that takes the complex ratio of the measured potential and current signals time-resolved complex impedance can be obtained. We will discuss the differences between the Li cycling profiles using Lipon (a glassy solid electrolyte) and a liquid electrolyte. We will relate the differences in cycling performance, particularly the SEI evolution to the surface chemistry of the as-received Li metal source.

The US Department of Energy's Energy Efficiency and Renewable Energy Vehicles Technologies Office provided funding for this work under the US-German Cooperation on Energy Storage: Lithium-Solid-Electrolyte Interfaces program.
Stable Organic Radical for Enhancing Metal-Monolayer-Semiconductor Junctions Performance
Authors: Fabre Bruno , De Sousa Jesus Alejandro , Pfattner Raphael , Rovira Concepcio , Mas-Torrent Marta , Crivillers Nuria
Published: September 2023

Among the large amount of families of molecules investigated in molecular junctions (MJs), stable free organic radicals have gained an increasing attention over the last years.1 Thanks to their open-shell electronic configuration, these molecules are paramagnetic, redox and optically active, which make them appealing species for a variety of applications.2 Chlorinated trityl radicals, and in particular the perchlorotriphenylmethyl radicals have shown to be highly stable as active molecular units in MJs.3 Such functional molecules have been recently covalently bound to photoactive, hydrogen-terminated silicon surfaces and the so modified surfaces have been demonstrated to function as light-triggered capacitance switches with good stability.4

Herein, the charge transport of these systems, employing the open- and closed-shell molecules (Rad-PTM and αH-PTM, Figure 1a), is investigated as solid-state Metal/monolayer/Semiconductor (MmS) junctions using an eutectic Gallium-Indium liquid metal as the top electrode. A characteristic diode behavior is observed which is tuned by the electronic characteristics of the organic molecule. Our results clearly indicate that the presence of the SOMO-SUMO molecular orbitals impacts on the device performance. The junction incorporating the radical shows an almost two orders of magnitude higher rectification ratio (R = 104.04) in comparison with the non-radical one (R = 102.30) at ± 1 V bias. Interestingly, the high stability of the fabricated MmS permits to interrogate the system under irradiation, evidencing that at the wavelength where the photon energy is close to the band gap of the radical, there is a clear enhancement of the photoresponse.5

(1) Ratera, I.; Vidal-Gancedo, J.; Maspoch, D.; Bromley, S. T.; Crivillers, N.; Mas-Torrent, M. J. Mater. Chem. C
2021, 9, 10610–10623.

(2) Mas-Torrent, M.; Crivillers, N.; Mugnaini, V.; Ratera, I.; Rovira, C.; Veciana, J. J. Mater. Chem.
2009, 19, 1691–1695.

(3) Bejarano, F.; Olavarria-Contreras, I. J.; Droghetti, A.; Rungger, I.; Rudnev, A.; Gutiérrez, D.; Mas-Torrent, M.; Veciana, J.; Van Der Zant, H. S. J.; Rovira, C.; et al. J. Am. Chem. Soc.
2018, 140, 1691–1696.

(4) De Sousa, J. A.; Bejarano, F.; Gutiérrez, D.; Leroux, Y. R.; Nowik-Boltyk, E. M.; Junghoefer, T.; Giangrisostomi, E.; Ovsyannikov, R.; Casu, M. B.; Veciana, J.; et al. Chem. Sci.
2020, 11, 516–524.

(5) De Sousa, J. A.; Pfattner, R.; Gutiérrez, D.; Bromley, S. T.; Veciana, J.; Rovira, C.; Mas-Torrent, M.; Fabre, B.; Crivillers, N. ACS Appl. Mater. Interf., submitted.

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(Invited) Bioelectrochemical Strategies for C-H Activation
Authors: Minteer Shelley D.
Published: September 2023

Petroleum hydrocarbons are currently our major energy source and an important feedstock for the chemical industry. Beyond combustion, conversion of chemically inert hydrocarbons to more valuable chemicals is of considerable interest. However, two challenges hinder this conversion. One is the regioselective activation of inert carbon–hydrogen (C–H) bonds. The other is designing a pathway to realize this complicated conversion. This paper will discuss the use of alkane monoxygenases in bioelectrochemical systems for C-H activation, as well as enzyme cascades and hybrid catalytic cascades for the conversion of inert alkanes to complex organic molecules like imines with selectivity far beyond traditional homogeneous and heterogeneous catalysts.
(Invited) Unique Size-Dependent Electrochemistry of Metal Nanoparticles in Aqueous and Hydrogel Environments
Authors: Zamborini Francis , Nambiar Harikrishnan , Waidyaratne Dilmi , Amechi Miracle , Singh Rajiv
Published: September 2023

Metal nanoparticles (NPs) exhibit unique size-dependent physical and chemical properties, providing many potential applications including sensing, catalysis, optoelectronics, medical diagnostics and disease therapeutics, among others. Here we describe interesting size-dependent metal oxidation, metal reduction, and electrocatalytic properties for Au and other metal nanoparticles that are coated with relatively weak-binding stabilizers, which is necessary for effective electron transfer at the metal NP surface. Metal oxidation potentials decrease dramatically negative with decreasing NP size, especially below 4 nm down to ~1 nm in radius. Electrocatalytic seeded-growth kinetics also depend strongly on the metal NP size (seed size). The thermodynamics of other oxidation/reduction reactions, such as galvanic replacement, also depend dramatically on metal NP size, resulting in unique alloy nanostructures with improved electrocatalytic reactivity and stability. Size-dependent electrophoretic deposition of metal nanoparticles to form thin films also results from size-dependent electrocatalytic properties, allowing metal NP separations based on electrocatalytic activity. These oxidation, reduction, galvanic replacement, and electrocatalytic properties change dramatically when the metal NPs are coated with strong ligand stabilizers or when placed in a viscous hydrogel environment. The effect of the ligand and environment will be described here. A better understanding of size-dependent reactivity of metal NPs as a function of the type of stabilizer and environment is important to realize their potential for tuning the properties to optimize them for a specific application.
(Invited) Lessons in Electrode Architecture for Faradaic Desalination
Authors: Long Jeffrey W. , Neale Zachary G. , Hunt Rebecca A. , DeBlock Ryan H. , Sassin Megan B. , Rolison Debra R.
Published: September 2023

Potable water is an essential supply for humanitarian missions worldwide, yet delivering pre-purified water to remote locations is challenging, dangerous, and expensive. Therefore, it is desirable to develop and deploy on-site and portable desalination/water-purification equipment that draws on local water sources. Present reverse-osmosis systems effectively desalinate seawater, but are energy and time-intensive, require regular maintenance due to membrane fouling, and suffer from poor scalability. Capacitive deionization (CDI) technology provides energy-efficient desalination of brackish waters, but its use remains limited by low-capacity carbon-only electrodes that rely on double-layer ion storage. Transitioning to electrodes that also incorporate Faradaic ion-capturing materials with substantively higher storage capacity expands the efficacy and applicability of CDI. As one example, NRL-developed porous carbon nanofoam (CNF) architectures infiltrated with electrolessly deposited nanometric MnO2 demonstrate 6-fold increase in sodium-ion adsorption capacity compared to bare-carbon CNFs, while solvothermally deposited BiOCl renders a high-capacity chloride-ion adsorption electrode. The tunability of CNFs as an electrode scaffolding affords the opportunity to balance ion-storage capacity and electrolyte transport for optimized desalination performance. Lessons of electrode architecture extend to NRL silver “sponge” electrodes that provide high capacity for chloride, fast uptake dynamics, and opportunities for various flow configurations. Continued progress in bench-top level flow-cells with high-capacity faradaic materials will demonstrate the promise of this technology en route to development of larger-scale prototype desalination devices.
(Invited) Enhancing the Performance of Microbial Fuel Cells Via Metabolic Engineering of Escherichia coli for Phenazine Production
Authors: Simoska Olja , Minteer Shelley D.
Published: September 2023

Establishing an efficient and successful extracellular electron transfer (EET) between microorganisms and electrode surfaces plays a critical role in the design, development, and application of mediated microbial electrochemical technologies, such as microbial fuel cells (MFCs). Most microbial-based systems require the use of artificial, redox-active mediator systems in order to facilitate and/or increase electron transfer. Our previous work established an exogenous phenazine-based library as a mediator system to enable electron transfer from the model microorganism Escherichia coli. However, the addition of exogenous mediators to a microbial electrochemical system has certain limiting downsides, specifically with regard to mediator toxicity to cells and increased operational expenses. Herein, we demonstrate the metabolic and genetic engineering of E. coli to self-generate phenazine metabolites endogenously by introducing the phenazine biosynthetic pathway from Pseudomonas aeruginosa into E. coli. This pathway consists of a seven-gene phenazine biosynthetic cluster phzA-G responsible for the synthesis of phenazine-1-carboxylic acid (PCA) and two phenazine accessory genes phzM and phzS to produce pyocyanin (PYO). We present the characterization of the engineered E. coli cells via electrochemical measurements, RNA sequencing, and microscopy imaging. Finally, the engineered E. coli cells were used for the design of a microbial fuel cell with enhanced performances, demonstrating a maximum power density increase from 305 mW/m2 with non-engineered E. coli cells to 1555 mW/m2 with the genetically engineered, phenazine-producing E. coli. Our results indicate that introducing a heterologous electron shuttle into E. coli can be an efficient approach to establishing efficacious mediation in living bioelectrochemical systems and improving the performance of MFCs.
Electrochemical Colloquium and Beyond: Opportunities for Online Education in Electrochemistry
Authors: Akbashev Andrew
Published: September 2023

Electrochemistry represents an exceptionally multifaceted and hard-to-teach subject. First, it requires knowledge of very distinct fields, including chemical thermodynamics, surface science, quantum mechanics, solid state ionics, catalysis, photovoltaics, cellular biology, and others. As a result, no electrochemistry curriculum can cover all the material needed for comprehensive understanding of the subject, meaning that the course is often shaped by the teacher’s personal preferences and agenda (e.g., fundamental electrochemistry, energy storage, corrosion, bioelectrochemistry, etc.). Second, the very core of electrochemistry – electrical double layer – is heavily debated within the professional community and does not have a satisfactory and consensual description suitable for textbooks and teaching. Unlike the kinetics of molecular reactions in solutions or at gas-solid interfaces, the kinetics of electrochemical reactions with the double layer region, even in simplest cases, is almost impossible to predict from first principles. All this causes confusion among both students and teachers – how should we teach when the key concept cannot be described adequately? Third, the field of electrochemistry is evolving, older concepts are reconsidered, and the new ones are introduced. This makes it difficult for students to relate course material to what is going on in real research. Finally, electrochemistry is vital for industry, which makes it particularly tempting for teachers to introduce a substantial “engineering” component into the curriculum and turn it into “applied electrochemistry course” (covering energy storage and conversion, corrosion, electroplating, etc.). While being well-intended, this leads to oversimplification of electrochemistry and offers a general (and often confusing) overview of the field.

In my talk, I will discuss the difficulties of teaching electrochemistry courses and how online platforms can offer possible solutions. Specifically, I will draw on my experience with the Electrochemical Online Colloquium, which aims to make fundamental science and essential knowledge freely accessible to the public. My argument is that a holistic understanding of electrochemistry cannot be achieved if one ignores knowledge gained in neighboring fields. At the same time, discussion of open questions and critical assessment of concepts by experts helps a student understand what is truly well-established in the field and what is not. I will also discuss future opportunities for online education in electrochemistry and how we can improve the quality of research in this field.
Teaching Electrochemical Science and Engineering Online
Authors: Bazant Martin Z.
Published: September 2023

In many schools of science and engineering where electrochemistry is beginning to play a major role in research and advanced study, it is still missing from the curriculum, especially at the undergraduate level. One way to address this problem and draw students into electrochemistry is to teach online. This talk will describe the teaching of electrochemistry online at MIT by two different approaches: free course materials for 10.626/10.426 Electrochemical Energy Systems on OpenCourseWare and massive open online courses (MOOCs) for 10.50 Analysis of Transport Phenomena on edX and MITx Online.
Electrochemistry in the Teaching Laboratory to Synthesize and Evaluate Catalysts for Water Oxidation and Reduction
Authors: Young Elizabeth R
Published: September 2023

Electrochemical analysis is an important skill to teach in chemistry curricula because it is a critical tool in current high-impact chemical research. Electrochemistry enables researchers to analyze a variety of systems extending from molecules to materials that encompass research themes ranging from clean energy to substrate activation in biological systems. Specifically, it can reveal information about catalytic efficiency, the role of catalysts, and the nature of chemical reduction and oxidation (redox) processes. Researchers working in the area of catalysis rely heavily on electrochemistry, using it to identify effective catalysts and to optimize reaction conditions. This talk with describe a laboratory experiment designed for undergraduate chemistry majors. The laboratory experiment begins with an introductory tutorial to electrochemistry by guiding students through the use of several electrochemical techniques using the ferricyanide/ferrocyanide redox couple as a model system. The techniques covered in the tutorial include cyclic voltammetry, differential pulse voltammetry, Tafel analysis, and bulk electrolysis. The protocol then applies these techniques to electrocatalysis by identifying and characterizing catalysts for hydrogen and oxygen generation in the water electrolysis reaction. Electrochemical methods are connected to current chemical research by focusing on catalysis in the context of renewable energy, which is a current societal and curricular imperative. The entire laboratory protocol is suitable for upper-level physical, analytical or inorganic chemistry.

Figure 1
Visualizing 3D Data with Merge Cubes
Authors: Coduto Joshua Richard , Lazicki Andy Peter , Leddy Johna
Published: September 2023

Education in chemistry often requires students to interpret and manipulate data across three dimensions. In electrochemistry, 3D information can take the form of surface profiles, potential axes, Reinmuth plots, and more. While some students are adept at visualizing and interacting with complex 3D data, others struggle to do so. This creates a barrier and can prove a disadvantage in advanced chemistry courses. To better aid student understanding, Merge Cubes, an augmented reality tool, are introduced to an analytical chemistry course with a focus on equilibrium and electrochemistry. Students can view 3D objects with the smartphone companion app, where objects are superimposed on the cubes and displayed on the phone. The objects can be rotated, manipulated, and annotated to give a better understanding of 3D data. Objects are provided to students throughout the course, showing equilibria, titrations, potentiometry, and voltammetry in 3D space. The objects are used as introductory tools for content, visual aids for graded assignments, and as discussion activities. Student opinion surveys for each content module provide information on the efficacy of Merge Cubes and what format students found most helpful.

Figure 1
Mechanistic Insights into the Kinetics of Hydrogen Evolution Reaction on Au@Nis Yolk@Shell Nanocrystals
Authors: Kuo Hsuan Hung , Hsu Yung-Jung
Published: September 2023

In order to resolve the energy issue, green and renewable energy demand is increasing rapidly. Hydrogen is thought as a clean energy fuel to replace traditional fossil fuels and it can be produced by electrocatalysis from hydrogen evolution reaction (HER). However, traditional HER uses Pt or Pt-based material as working electrode, which is highly costly and thus not desirable for practical applications. Recent developments have showed that transition-metal sulfides, phosphides and selenides can perform superior HER over noble metals with good stability and even dual function enabling overall water. In this work, we have synthesized Au@NiS yolk@shell nanocrystals for efficient HER. The pronounced electronic interactions between Au and NiS can facilitate interfacial charge transfer to promote the kinetics of HER. In-situ X-ray absorption spectroscopic measurements were conducted to explore the working mechanism of HER over Au@NiS. The HER performance and durability in a wide range of pH is also tested in order to demonstrate the wide application scenarios.
(Keynote) Electrochemical Proton-Coupled Electron Transfer Theory
Authors: Hammes-Schiffer Sharon
Published: September 2023

Proton-coupled electron transfer (PCET) plays a vital role in a wide range of electrochemical processes. This talk will describe theoretical and computational methods that have been developed to study electrochemical PCET and a variety of applications to molecular and heterogeneous electrocatalysis. My group has formulated a general PCET theory that includes the quantum mechanical effects of the electrons and transferring protons, as well as the motions of the donor-acceptor modes and solvent or protein environment. This PCET theory enables the calculation of rate constants and kinetic isotope effects for comparison to experiment. Our extension of this theory to electrochemical PCET incorporates the electronic structure of the electrode and the interfacial electric fields arising from the electrical double layer. Theoretical formulations for both homogeneous and heterogeneous electrochemical PCET provide analytical expressions for the rate constants and current densities as functions of applied potential. This theory has been applied to proton discharge on metal electrodes, as well as PCET at metal oxides and graphite-conjugated catalysts. These applications highlight the importance of using a theory that quantizes the transferring proton and includes the effects of hydrogen tunneling and excited electron-proton vibronic states. The insights from these theoretical studies are useful for the design of electrocatalytic systems to control the movement and coupling of electrons and protons for energy conversion processes.

References

Venkataraman, A. V. Soudackov, and S. Hammes-Schiffer, Theoretical formulation of nonadiabatic electrochemical proton-coupled electron transfer at metal-solution interfaces, J. Phys. Chem. C
112, 12386-12397 (2008).

K. Goldsmith, Y. C. Lam, A V. Soudackov, and S. Hammes-Schiffer, Proton discharge on a gold electrode from triethylammonium in acetonitrile: Theoretical modeling of potential-dependent kinetic isotope effects, J. Am. Chem. Soc.
141, 1084-1090 (2019).

C. Lam, A. V. Soudackov, and S. Hammes-Schiffer, Kinetics of proton discharge on metal electrodes: Effects of vibrational nonadiabaticity and solvent dynamics, J. Phys. Chem. Lett.
10, 5312-5217 (2019).

E. Warburton, P. Hutchison, M. N. Jackson, M. L. Pegis, Y. Surendranath, and S. Hammes-Schiffer, “Interfacial field-driven proton-coupled electron transfer at graphite-conjugated organic acids,” J. Am. Chem. Soc.
142, 20855-20864 (2020).

E. Warburton, A. V. Soudackov, and S. Hammes-Schiffer, Theoretical modeling of electrochemical proton-coupled electron transfer, Chem. Rev.
122, 10599-10650 (2022).
Mechanistic Insights into Ion Transport in Polymerized Ionic Liquids
Authors: Zhu Zhenghao , Popov Ivan , Sokolov Alexei P. , Paddison Stephen J.
Published: September 2023

Polymerized ionic liquids (polyILs) continue to be of great interest as electrolytes in energy conversion and storage devices. However, challenges in enhancing the ionic conductivity to ~10-3 S/cm still hinder the application of these materials. Therefore, it is urgent to improve the conductivity in these electrolytes, which strongly relies on advances in molecular-level understanding of ion transport mechanisms governing charge transport. To this end, ionic correlations and the mechanisms of ion transport in the polyILs and their corresponding ILs have been systematically studied by altering the molecular chemistry of the cation and the anion using classical molecular dynamics simulations.

We first hypothesized that immobilization of one of the ions in the polymer may lead to a significant increase in negative correlations in the dynamics of the mobile ions. To verify this hypothesis, we used a polymethylmethacrylate (PMMA) based backbone with attached imidazolium cations and mobile anions, including TFSI−, PF6
−, BF4
−, and Br−. The increase in temperature enhances both intrachain and interchain ion hopping while reducing the rattling of mobile ions. The analysis of ionic correlations in both ILs and polyILs systems at various temperatures revealed that the inverse Heaven ratio was not temperature dependent in either of the systems. We further investigated the effect of side-chain flexibility of polyILs on ionic correlations by changing the side-chain length. The higher flexibility enhances local mobility of the imidazolium cations, leading to an increasing number of associating cations from more polymer chains to the anions. Another key factor in tuning ionic correlations in concentrated ionic systems is electrostatic interactions, whose role was investigated by changing the dielectric constant of the simulated systems. We believe these molecular-level insights will advance the rational design of novel polyILs for electrochemical applications.