bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Relays in Nanometer Scale Alumina: Effective Protection Layers for Water-Submersed Halide Perovskite Photocathodes
Authors: Edri Eran , Harari Yuval , Shakher Pathak Chandra
Published: February 2024

Halide perovskite (HaP) solar cells have an excellent voltage efficiency (>70%) and a low electron-affinity conduction band minimum, making them prospective candidates to be used as photocathodes in integrated low-cost solar fuel generators. However, halide perovskites are notoriously unstable in aqueous solutions and immediately dissolve upon exposure to liquid water. Ultrathin layers (< 10 nm) of Al2O3 deposited by atomic layer deposition are suitable encapsulants to prevent water ingression but are also electronically insulating. Embedding linear conjugated organic molecules (‘molecular relays’) that transverse the insulating layer enables selective electron transport across the insulating encapsulating layer. The electronic functionality of the embedded molecular relays is verified by conductive probe atomic force microscopy and photo-electrodeposition of metal particles (Pt and Ag) from ethanolic solutions. Lastly, the encapsulated HaP photoelectrodes were submersed in a CO2-saturated aqueous electrolyte and a photocurrent of ~100 µA/cm2 (at ~ -0.32 V vs. Ag/AgCl) was measured. This work demonstrates a way for stabilizing semiconductors in polar and protonic electrolytes as photoelectrodes for the generation of solar fuels.
(Invited) Surface and Structural Dependent Reactivity of Alkylphosphonic Acids-Modified Titanium Oxide Nanostructures with 2-Chloroethyl Ethyl Sulfide Under Visible Light Excitation
Authors: Baturina Olga A , Giles Spencer , Purdy Andrew P , Ratchford Daniel , Maza William A
Published: February 2024

Synthesizing novel TiO2 nanomaterials are valuable for heterogeneous reactivity to address toxic chemical remediation. Titanium oxide nanoflowers (comprising assemblies of nanorods) and nanowires have been synthesized in which photocatalytic reactivity with 2-chloroethyl ethyl sulfide (2-CEES) has been significantly enhanced under visible light (1000 nm > λ > 400 nm) excitation. Enhancement of photooxidation with reaction rates of 99 and 168 µmol/g/h (quantum yields of 5.07 x 10-4 and 8.58 x 10-4 molecules/photon) were observed for TiO2 synthesized in the presence of two different alkylphosphonic acids (C14H29PO3H2 and C9H19PO3H2). Additionally, H2Ti2O5‧H2O nanowires were synthesized and capable of highly efficient hydrolysis of the carbon-chlorine (C-Cl) bond of 2-CEES without light at a reaction rate of 279.2 µmol/g/h due to high surface area and chemical nature of the titanate structure. These observations are correlated with: 1) generation of new surface defects/states (i.e. oxygen vacancies) as a result of TiO2 grafting by alkyl phosphonic acid that may serve as reaction active sites; 2) better light absorption by assemblies of nanorods in comparison to individual nanorods, 3) surface area differences, and 4) the exclusion of OH groups due to the formation surface functionalization with alkylphosphonic acids via Ti-O-P bonds on the TiO2. These robust materials can be used for highly efficient surface decontamination.
Current-Voltage Analysis Tool for Solar Fuel Production (CATS)
Authors: Kistler Tobias
Published: February 2024

Solar-driven electrochemical devices, such as PV-electrolyzers and photoelectrochemical (PEC) devices, contain multiple components which can make it difficult to pinpoint the failing piece when overall device performance is degrading. The current-voltage analysis tool for solar fuel production (CATS) is a free app that analyzes current-voltage data collected during operation, parameters that are easily accessible for many devices of interest. The program captures the time-dependence of loss mechanisms at play during PEC device operation and opens the door for real-time optimizations of operational parameters like the feed humidity to minimize performance losses. Aside from the possibility of deconvoluting loss mechanisms, this software can also reveal possible performance benefits, such as by convective PV cooling when the photoabsorber is integrated into the electrolysis cell.
The Influence of Electrochemical Bias on the Exciton Dynamics of MoS2 thin Films
Authors: Samu Gergely Ferenc , Toth Peter , Sárosi Krisztina , Mogyorósi Károly , Gilicze Barnabás , Seres Imre , Bengery Zsolt , Jójárt Péter , Chikán Viktor , Janaky Csaba
Published: February 2024

2D transition metal dichalcogenides are an attractive family of materials in the field of electronics and optoelectronics. They are excellent candidates for sensitive photodetectors, light harvesting devices (photovoltaics, photocatalysts or photoelectrodes), lasers or non-linear optical devices. All these applications rely on light-matter interactions, which processes will ultimately decide the efficiency of the derived devices. Understanding carrier dynamics and the interaction of various exotic quasi-particles (excitons, trions) in these materials is of paramount importance to design better performing devices.

Pump-probe transient absorption/reflection spectroscopy (TAS/TRS) is a powerful technique to study photophysical processes involved in charge carrier generation and recombination on the ultrafast timescale. In MoS2 photoelectrodes after light excitation different types of excitons are generated, and their decay can be monitored with these techniques. Coupling electrochemical techniques with these ultrafast methods, allows to probe the decay of the excited state in these materials under working conditions. In this manner the effect of trap state filling [1] or the effect of charge extraction [2] on the charge carrier dynamics of photoelectrochemical systems can be revealed.

In my presentation I will show ultrafast spectroelectrochemical measurements on ITO/MoS2 photoelectrodes and reveal how the decay of excitons are influenced by the applied electrochemical bias. By comparing results from TAS/TRS spectroscopy the separation of carrier dynamics on the surface and bulk of these systems can be performed. These measurements reveal that the dissociation of excitons occurs at the ITO/MoS2 interface, resulting in a long living exciton population on the surface of these samples. Charging/discharging studies carried out in these systems reveal that the trap states involved in the dissociation of excitons in these systems can be permanently filled. The electrochemical filling of these trap states allows the tuning of the excited state lifetime of these systems, which can aid the better design of photoelectrochemical devices based on MoS2.

References

[1] ACS Energy Lett. 2019, 4, 3, 702–708

[2] J. Am. Chem. Soc. 2018, 140, 1, 86–89
Tandem Semiconductor Microwire Slurries for Solar Hydrogen Generation
Authors: Gulati Saumya , Mulvehill Matthew , Spurgeon Joshua M.
Published: February 2024

Meeting the industry goal of $2/kg for solar H2 is a daunting task that will require novel, highly efficient systems which eliminate many of the components and balance-of-systems costs inherent with photovoltaics + electrolyzers. Technoeconomic models have consistently shown that a photoactive slurry reactor for water-splitting could offer the cheapest route to storing solar energy as hydrogen fuel. However, abundant challenges with this approach have thus far limited such particle-based reactors to prohibitively low efficiencies. This talk will highlight our progress toward the development of a tandem semiconductor particle system designed to address the weaknesses of slurry reactors and achieve a high solar-to-hydrogen (STH) efficiency for particle systems. A proof-of-concept tandem structure uses silicon microwires as the base of the particle, with a wider bandgap TiO2 layer grown on top to gain the additional photovoltage necessary to split water. Semiconductor architecture development and performance will be discussed along with early modeling efforts. In-situ magnetic alignment of the particles has been demonstrated for possible improved tandem light management. In addition, slurry optical characterization and photoelectrochemical performance will be discussed as a function of slurry parameters including bubble flowrate, particle concentration, spectral conditions, and light management strategies. Slurry conditions for minimizing back reactions will be discussed as well.
(Invited) Electrosynthesis of Long-Chain Hydrocarbons and Oxygenates
Authors: Yeo Boon Siang Jason
Published: February 2024

The electroreduction of CO(2), driven by renewable electricity, can be used to sustainably generate synthetic fuels and chemical feedstocks. Long carbon chain molecules are of particular interest due to their high energy densities and utilities. However, to date, most of the CO(2) reduction products formed are limited to C2 and C3. Herein, we discuss the development of electrocatalysts for the reduction of CO(2) to long-chain oxygenates and hydrocarbons, and their underlying reaction mechanisms.

CO(2) electroreduction has been previously reported to yield a range of carbonaceous products including alcohols, hydrocarbons and carboxylic acids. Interestingly, esters, an important family of organic compounds, have not been formed. We show how C3–C6 acetate esters could be produced from CO reduction in a membrane electrode assembly (MEA) cell. The near water-free reaction environment and the high local pH in the MEA played key roles in forming the esters with a Faradaic efficiency of 22 % and a current density up to −55 mA cm−2. We also disclose that inorganic nickel oxygenate (INO)-derived electrocatalysts can reduce CO2 to linear and branched C3-C6 hydrocarbons with Faradaic efficiencies up to 6.5%. We identified Niδ+ active sites which bind CO moderately. Our results show that Ni atom polarization to be important in hindering CO poisoning of nickel and thus facilitating CO2 reduction to a wider pool of valuable products.

Finally, we show how MgAl layered double hydroxide (LDH) nanosheets ‘House-of-cards’ structures help to disperse CuO-derived Cu (OD-Cu) catalysts. The porous structures formed enhanced CO gas percolation through the catalyst layer. OD-Cu dispersed by the ‘House-of-cards’ structures catalysed CO electroreduction to C2+ products with a partial current density that is an order of magnitude higher than that shown by the unsupported OD-Cu.

References:

1) Kwon, et al. Angew. Chemie Int. Ed. 62, e202217252. 2023

2) Zhou, et al. Angew. Chemie Int. Ed. 61, e202202859. 2022.

3) Zhou, et al. Nature Catal. 5, 545. 2022.
(Invited) Electrocatalysts and Processes for Carbon Dioxide Reduction
Authors: Mueller Astrid M
Published: February 2024

Efficient and robust electrocatalytic processes that convert climate-damaging carbon dioxide into useful fuels and chemicals are essential to decarbonize our economy. The accelerated discovery of effective catalysts critically depends on rational materials design, predicated on mechanistic and structural understanding of catalysts, electrode–electrolyte interfaces, and mass transport and catalytic processes. New synthetic methods are needed that enable the preparation of tailored multimetallic nanomaterials with precisely controlled properties, for which pulsed laser in liquids synthesis is an ideal tool. Laser-made catalysts are intrinsically more active than analogs made by conventional equilibrium methods.[1] For electrolyzer devices, nanoparticulate catalysts must be immobilized on inert, high surface area carbon substrates for electrocatalysis in aqueous electrolytes. We solved this challenge by preparing carbon fiber paper with intact mesostructures and long-lasting hydrophilicity by a green chemistry process.[2] We developed novel copper-free trimetallic electrocatalysts for aqueous carbon dioxide reduction [3] that produced C–C-coupled products. Systematic variation of metal ratios revealed trends in product distributions. We also assessed gold nanoparticle–hydrophilic carbon fiber paper assemblies with ionomer overlayers for clean syngas generation. Our laser-made catalysts together with the newly developed ability to use them on high surface area electrode supports provide the foundation towards the realization of viable successor technologies.

References:

[1] R.C. Forsythe, C.P. Cox, M.K. Wilsey, A.M. Müller. Pulsed Laser in Liquids Made Nanomaterials for Catalysis. Chem. Rev.
2021, 121, 7568-7637.

[2] M.K. Wilsey, K.R. Watson, O.C. Fasusi, B.P. Yegela, C.P. Cox, P.R. Raffaelle, L. Cai, A.M. Müller. Selective Hydroxylation of Carbon Fiber Paper for Long-Lasting Hydrophilicity by a Green Chemistry Process. Adv. Mater. Interfaces
2023, 10, 2201684.

[3] M.K. Wilsey, C.P. Cox, R.C. Forsythe, L.R. McCarney, A.M. Müller. Selective CO2 reduction towards a single upgraded product: a minireview on multi-elemental copper-free electrocatalysts. Catal. Sci. Technol.
2021, 11, 416-424.
Carbon Dioxide Reduction on Alloyed Galinstan
Authors: Mohamed Aya , Bogdanoff Peter
Published: February 2024

Solar powered electrochemical CO₂ reduction to disposable products is presently being developed as one of negative carbon emission technologies1. State-of-the-art electrocatalysts are mainly developed for the CO2 reduction to hydrogen rich products or chemical feedstock materials while for the above-mentioned application solid carbon-rich products are desired (best pure carbon). Even though the formation of solid products is sometimes observed on catalysts (coking effect), this usually leads to an undesirable irreversible deactivation of their solid interfaces.

Thus, the development of next generation CO2 electrocatalysts is demanded based on liquid metal alloys such as galinstan (GaInSn). The advantage of using liquid phase electrodes is to eliminate coking and coarsening limitations that are associated with solid catalysts. For example, it has been reported that ceria-supported liquid galinstan can electrochemically produce carbonaceous materials from CO2 gas2. This shows, that doping with additional active elements can change the CO2 reduction activity of GaInSn in the direction of other desired products.

Our work investigates the activity of galinstan for the electroreduction of CO2 depending on alloying with additional metals (such as Ce, Ag, Pb). While pure GaInSn shows a predominant activity for the formation of C1 products (CO, HCOOH) in DMF/H2O electrolyte, we are mainly interested in the formation of solid carbon or oxalate. Therefore, our investigations aim at finding suitable modifications of GaInSn that achieve high selectivity for these products. Electrochemical analysis coupled with in-line gas chromatography and in-line mass spectroscopy are used to characterize the reactivity. Furthermore, the influence of the water content of the organic electrolyte on the product selectivity will be investigated. In particular, to suppress the observed low hydrogen evolution as a by-product even more efficiently.

May, M. M.; Rehfeld, K., Negative Emissions as the New Frontier of Photoelectrochemical CO2 Reduction. Advanced Energy Materials
2022, 2103801.

Esrafilzadeh, D.; Zavabeti, A.; Jalili, R.; Atkin, P.; Choi, J.; Carey, B. J.; Brkljača, R.; O’Mullane, A. P.; Dickey, M. D.; Officer, D. L.; MacFarlane, D. R.; Daeneke, T.; Kalantar-Zadeh, K., Room Temperature CO2 Reduction to Solid Carbon Species on Liquid Metals Featuring Atomically Thin Ceria Interfaces. Nature Communications
2019,
10 (1), 865.

Figure 1
(Invited) Metal Oxide Nanoparticles for Stable Alkaline Oxygen Evolution Reaction in an Anion Exchange Membrane Electrolyser Cell
Authors: Farràs Costa Pau , Besic Hanka , Tong Wenming , Dionigi Fabio , Strasser Peter
Published: February 2024

One of the key challenges to develop efficient water electrolysis system is to find effective and robust electrocatalysts for the oxygen evolution reaction (OER). Mixed transition metal oxides provide immense possibilities for such purpose.1
,
2 Abundant catalytically active sites could be generated via engineering the defects and oxygen vacancies within the transition metal oxides.3 The catalyst stability could also be improved by incorporating self-healing component into the catalysts .4

In this work, we adopt cobalt oxides as substrate materials to prepare mixed transition metal oxides. The catalysts are synthesized via a combined approach of hydrothermal and annealing processes. The final products are characterized thoroughly by a broad range of characterization techniques, including XRD, TEM, SEM, EDX, and XPS. The OER activities are initially evaluated in a three-electrode system. The results show that the as-prepared catalysts demonstrate high current density at a relatively low overpotential. Moreover, the catalysts exhibit excellent robustness for an 8-hours stability test in a three-electrode testing system. The stability and activity of the catalysts is further assessed in a lab-scale anion exchange membrane (AEM) electrolyser cell setup. Only a small degradation is observed for the best performing catalyst in 12 hours period. The details of the catalyst characterization and electrochemical measurements will be discussed.

Acknowledgements

This work was funded by European Union’s Horizon 2020 projects FlowPhotoChem (Grant agreement number 862453) and European Innovation Council Pathfinder ANEMEL (Grant agreement number 101071111).

References

Mohammed-ibrahim, J. & Moussab, H. Tuning the electronic structure of the earth-abundant electrocatalysts for oxygen evolution reaction (OER) to achieve efficient alkaline water splitting – A review. J. Energy Chem.
56, 299–342 (2021).

Plevová, M., Hnát, J. & Bouzek, K. Electrocatalysts for the oxygen evolution reaction in alkaline and neutral media. A comparative review. J. Power Sources
507, (2021).

Zhang, R. et al. Tracking the Role of Defect Types in Co3O4 Structural Evolution and Active Motifs during Oxygen Evolution Reaction. J. Am. Chem. Soc. (2023) doi:10.1021/JACS.2C10515.

Silva, A. L. et al. Mn-doped Co3O4 for acid, neutral and alkaline electrocatalytic oxygen evolution reaction. RSC Adv.
12, 26846–26858 (2022).
(Invited) Energy Materials Development at Ceres: From Nanometers to Megawatts
Authors: Leah Robert , Hjalmarsson Per , Lankin Mike , De Vero Jeffrey , Donatus Uyime , Srivastara Raghav , Ray Santanu , McKenna Fiona-Mairead , Macauley Chandra , Mukerjee Subhasish , Hargrove Caroline , Selby Mark
Published: February 2024

Ceres’ unique metal supported SteelCell® SOC technology is increasingly establishing itself as the global standard for SOC, combining robustness, efficiency and low manufacturing cost. The technology is rapidly moving from demonstration to true volume production, with Robert Bosch GmbH in Germany and Doosan Fuel Cell in South Korea both having licenses to manufacture Ceres SteelCell® cells and stacks at the hundreds of MW per year scale with factories under construction. Ceres acts as design authority to licensees who manufacture Ceres-developed technology at scale. As such Ceres specifies the raw materials required for cell manufacture and has ultimate responsibility for the validation of any new suppliers of raw materials proposed by licensees.

In addition to supporting the high-volume scale up of current generations of SteelCell technology, Ceres has an extensive R&D program to develop future technology generations which offer improved performance, lower cost and/or lower degradation. A very detailed understanding of the behavior of the materials used in cells, stacks and systems is required to enable future optimization and/or the development of novel materials. This particularly includes the challenges of understanding degradation phenomena, which due to the extended timescales involved are poorly characterized in academic literature. To enhance this understanding Ceres has a number of academic collaborations, most notably with Imperial College London to use leading-edge experimental and computational techniques to understand material behavior affecting initial performance, degradation (particularly changes at interfaces) and corrosion of metallic components. Information gained from these collaborations is used to enable reliable lifetime prediction for current-generation stacks and systems to be undertaken using computer models to predict performance through-life using degradation models derived from theoretical understanding. Theoretical understanding of materials behavior also drives innovation in new generations of materials offering enhanced performance and/or durability, enabling Ceres to maintain its competitive advantage in SOC technology.
Quantum Yield of the Emission of Carbon Quantum Dots: Tricks Due to Solvent Polarity and Excitation Dynamics
Authors: Dimitriev Oleg , Kysil Dmitriy V. , Vasin Andriy V. , Zaderko Alexander N. , Kozakevych Roman B. , Nazarov Alexey N. , Furis Madalina
Published: February 2024

Carbon quantum dots (CQDs) are recognized as promising fluorescent nanomaterials possessing high thermal stability, tuned photoluminescence, along with the low cost of their production. Quantum yield (QY) of photoluminescence (PL) of CQDs is known to vary largely depending on the synthetic procedures/ chemical composition of CQDs, but there is still no unique approach for explanation of the nature and QY of PL emission of CQDs. Particularly, an accompanying effect of the solvent environment on QY of the PL emission is paid less attention. In this work, we compare photophysical properties of CQDs synthesized by different methods that resulted in the different composition of CQDs. First, fluoralkylated CQDs (Fluocar® Nano) doped with F, N and O heteroatoms, were synthesized via solvothermal method using urea, anhydrous citric acid and 3-(trifluoromethyl) aniline as precursors. Second, hydrophilic CQDs were obtained by liquid-phase synthesis procedure using sucrose (“standard” CQDs). Depending on the synthesis procedure the PL emission properties were tuned according to the polarity of solvent the CQDs were dispersed in. It was found that QY of PL emission of Fluocar® Nano has a much stronger magnitude and absolute dependence on the solvent polarity compared to “standard” CQDs. Fluocar® Nano demonstrated QY of PL emission as high as 93% in dioxane and as low as 30% in aqueous dispersion, whereas QY of the “standard” CQDs varied within 0.7-2.3% when relative solvent polarities ranged from 0.164 to 1.0; however, their relative changes depending on the solvent polarity were similar (Fig.1). Dynamics of the PL emission during first minute of excitation in the form of PL relaxation to some saturated value was also strong for Fluocar® Nano dispersed in less polar solvents, while the emission was stable in a strongly polar aqueous medium. Tentative conclusion was made that the surface of CQDs plays a crucial role in tuning the PL emission, providing different concentration of surface traps that become gradually fed during excitation and different interactions of CQD and polar solvents, respectively.

Figure 1
Nitric Oxide As a Signaling Molecule for Biofilm Formation and Dispersal in Mediated Electron Transfer Microbial Electrochemical Systems
Authors: Beaver Kevin , Dantanarayana Ashwini , Bonizol Zani Ana , Lehto Danielle L. , Minteer Shelley D.
Published: February 2024

With applications in bioremediation, biosensing, and bioenergy, microbial electrochemical systems are a rapidly growing, multidisciplinary field within biological, chemical, and materials science. Since these systems use living microorganisms as biocatalysts, it is important to understand how microbial physiology, namely biofilm formation, affects these electrochemical systems. Specifically, the literature lacks research that assesses the effects of biofilm on metabolic current output in mediated electron transfer systems. In this study, Rhodobacter capsulatus and Pseudomonas putida GPo1 were used as model, nonpathogenic strains that facilitate electron transfer via diffusible redox mediators. Nitric oxide has gained attention in biomedicine as a gaseous signaling molecule, which at sublethal concentrations may either augment or inhibit biofilm formation depending on the bacterial species. In R.
capsulatus, nitric oxide treatment was associated with increased current yield and improved biofilm formation. However, in P. putida GPo1, nitric oxide treatment corresponded to significantly reduced current output, as well as biofilm dispersal. In addition to highlighting the use of electrochemical tools to assess the effects of nitric oxide in biofilm formation, these findings demonstrate that biofilm-based mediated electron transfer systems benefit from the increased electrochemical output and enhanced cell adhesion, which is promising for more robust applications compared to their planktonic counterparts.

Figure 1
Electrochemistry and Organic Synthesis: New Adventures with Olefin Coupling Reactions and Electrode Surfaces
Authors: Moeller Kevin D , Feng Enqi , Krueger Ruby , Medcalf Zachary , Barzova Polina , Wagner Sarah
Published: February 2024

Electrochemistry has long offered opportunities to explore new modes of reactivity, new approaches for introducing selectivity into synthetic reactions, and new strategies for the synthesis of everything from complex molecules to complex, addressable molecular surfaces. In the talk to be given, two aspects of our efforts along these lines will be detailed.

In the first, we will take a look at recent efforts to use anodically-generated reactive intermediates to convert readily available small molecules into functionalized synthetic building blocks and natural product derivatives. Key to these efforts are oxidation reactions that generate reactive radical cation and radical intermediates. In one application, newly available chiral lactols synthesized using methodology developed by the Lin (Cornell) and Miller (Yale) groups are being transformed into C-glycoside and aza-C-glycoside derivatives. The reactions take advantage of oxidation reactions of either enol ether or vinylsulfide groups. The cyclization reactions and the subsequent deprotection strategy needed for converting the cyclization products into a useful synthetic building block will be highlighted.

In a second application of an anodic cyclization, the role of thioamides in reactions targeting the chrysosoporazine family of natural products will be discussed. The reactions seek to provide an efficient method for converting lignin derived building blocks into molecules that reduce the efflux of anticancer drugs from cells. Initial cyclization attempts utilizing amide based N-radicals and anodic olefin coupling reactions were not successful. Those reactions consistently led to over-oxidation of the products that contain a highly electron-rich aryl ring. The use of thio-amide derived radicals provides a method to circumvent this problem.

In the second topic to be discussed, the question of how one might begin to induce asymmetry into such electrochemical cyclizations will be highlighted. The chemistry focuses on efforts to influence the course of both electrochemical oxidation and reduction reaction and non-redox based transition metal catalyzed reactions with the surface of an electrode.
Single-Entity Bioelectrochemistry
Authors: Zhao Ziwen , Kostopoulos Nikolaos , Ganguli Sagar , Sekretareva Alina
Published: February 2024

Interfacing biological catalytic entities, such as whole cells or enzymes, with electrodes, has a wide range of applications, ranging from fundamental studies of the entities themselves to power generation, bioremediation, chemical synthesis, and biosensing. In all cases, the operation of these bioelectrocatalytic systems is based on electron transfer phenomena within protein molecules, whether isolated or residing inside cells or parts of cells, as well as between proteins and electronics. Typically, the electron transfer and catalytic properties of proteins are studied using ensemble averaging methods, which obscure any heterogeneity and dynamics of individual molecules. This information, however, is especially important for understanding electron transfer and catalytic processes within a living cell where only one or a few protein molecules are present. While single-entity electrochemical measurements are particularly useful for studying electron transfer reactions at the nanoscale level, they have limited applications for investigating biological entities due to the experimental challenges associated with direct measurements of small electrical currents. 1,2

Here we will discuss our recent progress in investigating biological electron transfer reactions at the single-entity level, from bacterial cells to single redox proteins, using nano-impact (collision) single-entity electrochemistry. 3 We demonstrate how advances in electrode fabrication methods and detection setups enable current detection in the fA range. When combined with the developed data processing algorithm based on unsupervised learning and template matching techniques, this enabled unprecedented insight into electron transfer processes at the nanoscale. We will talk about insights provided by the method in the study of several important bioelectrocatalytic systems: single E.coli cells with overexpressed Fe-Fe hydrogenases, single bilirubin oxidase molecules, and single catalase molecules. In addition, we will discuss models that we developed for understanding the single bioentity electrode interactions for diffusion-controlled enzymes when the product of the catalytic reaction is detected on the electrode, as well as systems based on direct electron transfer between the bioentity and the electrode. Overall, we show how single-entity bioelectrochemistry can shed light on biological electron transfer and catalysis processes and discuss the challenges it currently faces.

Zhang, J.-H.; Zhou, Y.-G. Nano-Impact Electrochemistry: Analysis of Single Bioentities. TrAC Trends Anal. Chem. 2019, 115768.

Davis, C.; Wang, S. X.; Sepunaru, L. What Can Electrochemistry Tell Us About Individual Enzymes? Curr. Opin. Electrochem. 2020, 100643.

Sekretaryova, A. N.; Vagin, M. Yu.; Turner, A. P. F.; Eriksson, M. Electrocatalytic Currents from Single Enzyme Molecules. J. Am. Chem. Soc. 2016, 138 (8), 2504–250
Sb2Se3-Based Photoelectrodes for Solar Hydrogen Production and CO2 Reduction
Authors: Dela Cruz John Mark Christian , Samu Gergely Ferenc , Janaky Csaba
Published: February 2024

Photoelectrodes with architecture FTO/Au/Sb2Se3/TiO2 for solar hydrogen evolution reactions (HER) and CO2 reduction reactions (CO2RR) were studied. The fabrication followed a simple spin-coating technique whereby nanorod-like structures were obtained for the Sb2Se3 as shown in the SEM images. A layer of TiO2 was deposited via ALD which acted as both an electron transfer layer and a protective coating. Pt and Au were deposited as co-catalysts and the photoelectrode performance for HER and CO2RR were investigated respectively (i.e., Pt for HER and Au for CO2RR). The photocurrent density achieved for HER reached 19 mA/cm2 at -0.35 V vs. RHE, while for CO2RR, it was 8 mA/cm2 at -0.5 V vs. RHE. The products detected for CO2RR were mainly hydrogen and CO with an average normalized distribution of 3:1 for hydrogen to CO. This set of initial experiments provide promising results for Sb2Se3-based photoelectrodes in solar-to-chemical applications.
(Invited) Insights into Processes at the Electrode/Electrolyte Interface of Battery Electrodes Via Scanning (Electrochemical) Probe Microscopy
Authors: Daboss Sven , Philipp Tom , Palanisamy Krishnaveni , Romer Jan , Kranz Christine
Published: February 2024

Scanning (electrochemical) probe microscopy (SEPM) techniques such as atomic force microscopy (AFM), scanning electrochemical microscopy (SECM), nano-pipette derived scanning probe methods like scanning electrochemical cell microscopy (SECCM) and hybrid methods have recently been used to study interfacial processes occurring at solid/electrolyte interfaces of battery electrodes [1]. So far, mainly Lithium-ion battery (LIB) electrodes have been studied, such as the solid-electrolyte interphase formation at graphite anodes [2,3]. Next generation battery chemistries, using earth abundant elements like sodium (Na), potassium (K), aluminum (Al) improving sustainability still suffer from insufficient knowledge of processes occurring during cycling at the electrode/electrolyte interface such as interphase formation, as gained insights from Li batteries cannot simply be transferred to post-Li chemistries.

In this contribution, an overview of the potential of SEPM techniques to gain insight in interfacial process of post-Li battery chemistries will be given, focusing mainly on the SEI formation on hard carbon composite anodes for Na-ion batteries (SIBs) [4]. The influence of the electrolyte composition along with the effects of additives on the SEI formation and the nanomechanical properties of the electrode will be presented. In addition, given the abundance of Al and the high theoretical volumetric capacity, makes Al a highly attractive battery chemistry [5]. Despite these advantages, there are several challenges like the Al2O3 passivating layer and the mostly used acidic ionic liquid (IL)-based electrolyte AlCl3/1-ethyl-3-methylimidazolium chloride [EMIm]Cl that leads to corrosion, which determines the plating and stripping efficiency and therefore the overall performance. First correlative SECCM/EDX/EBSD studies on Al anodes will be presented.

Acknowledgement

This work contributes to the research performed at CELEST (Center for Electrochemical Energy Storage Ulm - Karlsruhe) and was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – EXC 2154 – Project number 390874152 (POLiS Cluster of Excellence).

References

[1] S. Daboss, F. Rahmanian, H. S. Stein, C. Kranz, Electrochem. Sci. Adv. 2, e2100122 (2021).

[2] H. Bülter, F. Peters, J. Schwenzel, G. Wittstock, Angew. Chemie Int. Ed. 53 10531 (2014).

[3] G. Zampardi, S. Klink, V. Kuznetsov, T. Erichsen, A. Maljusch, F. LaMantia, W. Schuhmann, E. Ventosa, ChemElectroChem 2 1607 (2015).

[4] S. Daboss T. Philipp, K. Palanisamy, J. Flowers, H.S. Stein, C. Kranz, Electrochim. Acta ahead of print, (2023)

[5] H. Yang et al., Angew. Chem. Int. Ed. 58, 11978 (2019).
Continuum and Equivalent Circuit Modelling of Porous Electrode Charging
Authors: Janssen Mathijs , Pedersen Christian , Aslyamov Timur
Published: February 2024

The flow of electrolytes through pores is important in various fields of science and technology. Examples range from axons in the brain and plasmodesmata in plant cells to energy storage in batteries and supercapacitors. In the porous carbon electrodes of supercapacitors, ions move over micrometers through macropores until they arrive at nanopores, forming so-called electrical double layers. In this presentation, I discuss several models for this multi-scale charging process. First, I present analytical [1] and finite-element solutions [2,3] to the Poisson-Nernst-Planck (PNP) equation for the charging of cylindrical electrolyte-filled pores [Figure (a)]. With these methods, I will delineate the validity of the famous “transmission line” circuit model developed by de Levie in the 1960s [4,5] [Figure (b)]. The TL model assumes equipotential lines in a pore to be straight, which is not the case at a pore’s entrance and end, see Figure (a). As a result, the TL model does not accurately describe short-pore charging. Related, the impedance of short pores deviates from the impedance of the TL circuit (the “Warburg open” impedance Wo), especially at high frequencies, see Figure (c).

Figure Caption: (a) The electrostatic potential in a cylindrical pore next to an electrolyte reservoir of resistance Rb
shortly after applying a potential step. The data represent numerical solutions to the Poisson-Nernst-Planck (PNP) equations, which we solved with finite elements using a Newton solver from the FEniCS library. (b) The transmission line circuit is an equivalent circuit that describes the charging of pores such as the one shown in panel (a). In the circuit, the resistance R and capacitance C of the pore are cut into small pieces r and c. (c) The impedance of the TL circuit is given by Rb
+Wo
(blue dotted line), where Wo
is the Warburg open impedance. Also shown is the impedance of a pore whose length is five times its diameter, as obtained from numerical PNP simulations (black).

T. Aslyamov and M. Janssen, Electrochim. Acta 424, (2022)

J. Yang, M. Janssen, C. Lian, R. van Roij, J. Chem. Phys. 156, (2022)

C. Pedersen, T. Aslyamov, M. Janssen, in preparation

R. de Levie, Electrochim. Acta 8, (1963)

M. Janssen, Phys. Rev. Lett. 126, (2021)

Figure 1
Li-Ion Cell in Operando Monitoring and Prognostication Using CMUT Devices
Authors: Cannon Andrew
Published: February 2024

Capacitive micromachined ultrasonic transducer (CMUT) devices are ideal solutions for in operando battery monitoring applications especially for consumer electronics. Their minute size (2mm x 1mm x 0.5mm) allows direct placement on the battery without affecting the form factor of the device, the volume production techniques used for their manufacture allow for a very low-cost device, and they can be easily integrated with front-end integrated circuits either in a single device or in a discrete multichip form. Together with industry partners we have developed CMUT devices that we use to continuously monitor the behavior of a battery while it is cycling.

For this work we used CMUTs (close-up shown in Fig. 1(a)) developed to operate with a low bias voltage (less than 30 V) which reduces the complexity of the driving hardware. The impulse response and its frequency content are shown in Fig. 1(b). In collapse mode, the peak frequency is 4.0 MHz and the one-way –3 dB BW is 76%, which allows flexibility in setting the drive conditions to interrogate the battery. Our testing also shows that the CMUTs show good device-to-device uniformity and they have a very stable performance in variable temperature environments (e.g. 0℃ - 60℃ ).

The cell is interrogated in pulse-echo mode. The CMUT is excited by a wide-band unipolar pulse and the returned analog signal is filtered and amplified. The signal is then digitized and processed to extract features that allow us to quantify the state of the battery. Figure 1(c) depicts such signal features change under baseline cell cycling conditions (three cycles at a charge rate of C/4). These changes are the result of mechanical material property changes in the cell e.g., electrode stiffness and density [1] which directly affect the acoustic wave propagation inside the cell. Figure 1(d) depicts signal feature change due cell overcharge (red line). Ultrasound is especially sensitive to gas generation which occurs as the cell voltage extends beyond normal operating range [2]. Signal features provide early warning notice that cell is outside of normal operating conditions.

Figure 1. a) Close-up image of CMUT device. b) CMUT impulse response and corresponding frequency content. c) Signal features (RMS and Time of Flight (ToF)) and thickness change during C/4 charge and discharge. d) Signal features during cell constant current overcharge. Cell overcharged after 4.4V (red line).

Chang, W. et al. Measuring effective stiffness of Li-ion batteries via acoustic signal processing. Mater. Chem. A
8, 16624–16635 (2020).

Appleberry, M. C. et al. Avoiding thermal runaway in lithium-ion batteries using ultrasound detection of early failure mechanisms. Journal of Power Sources
535, 231423 (2022).

Figure 1
Detection of Covid-19 with Dual-Signal Probes in Paper Microfluidics
Authors: Xiong Helen , Hang Yingjie , Wu Nianqiang
Published: February 2024

Current Covid-19 detection methods commercialized today that use colorimetric probes have

the advantage of short response time but the issue of low sensitivity. Other methods consider

fluorescent probes that increase sensitivity but lead to longer response times. In this work,

both fluorescence probes and colorimetric probes are integrated into a microfluidic paper strip.

Both probes are incorporated into a single microfluidic paper strip to optimize sensitivity and

efficiency. As a result, the use of colorimetric probes allows for the advantages of antibody

absorption to be utilized for a short response time to detect antigens without need an extra

excitation source while fluorescent probes increase detection sensitivity and compensate for

the low sensitivity of colorimetric probes. The dual-signal probe displays capacity for greatly

improving the accuracy and timeliness of standard Covid-19 detection in test kits.
(Invited) Magnetofluidic Platforms for Point-of-Care Detection of Infectious Diseases
Authors: Wang Tza-Huei Jeff
Published: February 2024

Commercialized rapid POC PCR technologies are either too slow, lack antimicrobial resistance data, or are too costly for widespread adoption in resource-limited settings. This talk discusses the use of magnetofluidic platforms coupled with inexpensive disposable assay cartridges to automate, accelerate, and simplify PCR tests of infectious diseases. Instead of traditional fluidic strategies for sample handling and assay automation, magnetofluidic technologies use the movement of magnetic beads through discrete droplets of reagents to capture, purify, and transfer analytes for amplification and/or detection, eliminating the need for large, complex instrumentation and fluidics typically associated with clinical laboratory PCR tests. Miniaturized and focused thermal cycling enabled by magnetofluidic PCR significantly shortens the turnaround time of a DNA/RNA test to <15 min. We demonstrated the versatile use of portable magnetofluidic platforms for various infectious disease diagnostic applications, including POC detection of sexually transmitted infections and antimicrobial susceptibility, multiplex detection of SARS-CoV-2 and respiratory pathogens, and HIV viral load testing.
(Invited) Continuous Molecular Monitoring in Interstitial Fluid Via Wearable Microneedle Aptamer-Based Sensors
Authors: Arroyo Netz
Published: February 2024

The ability to continuously monitor the concentration of specific molecules in the body is a long-sought goal of biomedical research. For this purpose, interstitial fluid (ISF) has been proposed as the ideal target biofluid because its composition can rapidly equilibrate with that of systemic blood, allowing the assessment of molecular concentrations that reflect full-body physiology. To tap into this measurement compartment, it is possible to use microneedle sensor arrays for continuous molecular monitoring. In this presentation, I will discuss our efforts to develop microneedle-supported electrochemical, aptamer-based (E-AB) sensors. This platform allows affinity-based monitoring of target concentrations in ISF, and takes advantage of the versatility of aptamers to selectively bind a large variety of molecular targets. I will discuss our current state of platform development, including fabrication challenges, in-vivo deployment in rodent models, and variability of pharmacokineitc profiles as a function of microneedle penetration depth in the skin.
Fast Screening of Fentanyl Illicit Drug By the Electrochemical Enhancement of Raman Intensity
Authors: Ibáñez David , González-García María Begoña , Hernández-Santos David , Fanjul Pablo
Published: February 2024

Fentanyl is a potent opioid drug used as an analgesic and anesthetic because it is approximately 100 times more potent than morphine and 50 times more potent than heroin as an analgesic. However, the overdose of fentanyl requires small dose and can cause stupor, changes in pupil size, clammy skin, cyanosis, coma, and respiratory failure leading to death. During the last years the illicit fentanyl and its analogues have been responsible for most drug overdose deaths in different countries and for that reason, the development of identification and detection methods is mandatory.

Spectroelectrochemical methods are currently proposed for the screening of this drug [1]. For instance, the combination of electrochemistry (EC) and surface-enhanced Raman scattering (SERS) has received growing attention due to the enhancement of Raman intensity associated with EC-SERS effect. However, the generation of reproducible SERS substrates is a traditional limitation of this effect. In that way, activation of metallic screen-printed electrodes (SPEs) by electrochemical routes allows to obtain reproducible nanostructures with excellent SERS properties [2], opening new gates for analytical applications.

In this work, the development of a fentanyl detection method based on EC-SERS effect is achieved. Spectroelectrochemical screening of this drug with metallic SPEs consists of two consecutive steps performed in a single experiment: (1) electrochemical generation of metallic NPs with SERS effect and (2) Raman detection of fentanyl present in solution.

Metallic SPEs provide interesting results being not only useful in the characterization of fentanyl, but also for analytical purposes. The proposed EC-SERS method with gold SPEs allows the detection of 0.33 ug/ml fentanyl and offers a rapid, efficient, and accurate approach for the detection of this drug.

References

[1] C.E. Ott, M. Perez-Estebanez, S. Hernandez, K. Kelly, K.A. Dalzell, M.J. Arcos-Martinez, A. Heras, A. Colina, L.E. Arroyo, Frontiers in Analytical Science, 2 (2022) 1-12.

[2] D. Ibáñez, M. B. González-García, D. Hernández-Santos, P. Fanjul-Bolado, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 248 (2021) 119174.
Effect of Parasitic Gas Evolution Reactions on the All-Vanadium Redox Flow Battery Performance
Authors: Qian Xiao , Jung Seunghun
Published: February 2024

All-vanadium redox flow batteries (VRFB) as the most promising candidates for large-scale energy storage can overcome the inherent defect of natural energy, such as intermittent and fluctuating, et al. During the operation of VRFB, the parasitic gas evolution reactions (GERs) are unavoidable due to thermodynamic limitation, which yet will cause a series of issues, such as imbalance of state of charge (SOC), graphite electrode degradation, security risk, etc. To have a deeper understanding of the parasitic GERs in VRFB, the present work developed a transient, multidimensional, multiphysics VRFB model coupling the multiphase species transport and electrochemical reactions. The model was validated with in-house experimental data and published literature, which showed great consistency. Following, the temporal-spatial characteristics of GERs and their competition with main cell reactions were analyzed in detail under different charging current densities and electrolyte flowrate. The results showed that the rate of hydrogen evolution reaction (HER) at the negative electrode is several magnitudes higher than that of the oxygen evolution reaction (OER) at the positive electrode. Besides, the HER happens during the whole charge-discharge process since the activation overpotential remains negative while the OER occurs only at the end of the charging process under high charging current density. It is notable that the HER mainly occurs in the region near the bipolar plate and increases with increasing charging current density. Since HER is favored thermodynamically over the reduction reaction of trivalent vanadium ions, the activation overpotential of the HER remains much higher than that of the main cell reaction during the whole charge-discharge process, albeit the volumetric current density for hydrogen evolution accounts for only part of the overall current due to the limitation of the reaction kinetics. The HER increases with the SOC and causes a SOC imbalance of 0.54% within 10 charge-discharge cycles, thereby accounting for an 11.0% degradation in the VRFB’s capacity. A high current density decreases the amount of hydrogen generated during a charge-discharge cycle yet also causes hydrogen accumulation in the porous electrode due to faster hydrogen generation. The present work takes a comprehensive and detailed discussion about the characteristics of parasitic gas evolution reactions and their effect on the VRFB performance, which gives a deeper understanding of the energy loss mechanism of VRFB for its development and optimization.

Figure 1