bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman Spectroelectrochemical Studies of Vanadyl-Ion Oxidation on Carbon Paper Electrodes for Vanadium Redox Flow Batteries
Authors: Stevenson Keith J , Gvozdik Nataliya 
Published: July 2021

In this talk, we introduce a new spectroelectrochemical technique, which combines Raman spectroscopy with cyclic voltammetry as a powerful tool for deducing complex redox mechanisms on the real electrode surfaces. In particular, the vanadyl oxidation reaction mechanism was investigated on heat-treated carbon paper. Additional heating of carbon fiber electrodes led to a significant improvement in the electrochemical performance, which was attributed to the improved wettability and to the enhancement of charge transfer kinetics and the reactions’ pathways involving surface oxygen functional groups.
We found drastic differences in carbon paper electrodes reactivity activated at different temperatures which were due to different oxidation stability of carbon paper components: carbon fibers and the binder. The fibers were more susceptible to oxidation, while the binder burned and graphitized , which lead to a decrease in electrochemical active surface area and mechanical degradation. Both components of the electrode were well distinguished via spatially resolved Raman spectroscopy measurements. The monitoring of vanadyl oxidation showed two different reaction mechanisms on the fiber surface and the alternative one for the binder phase. Vanadium dimers were preferentially formed on the surface of partially oxidized fibers under low overpotential, while the growth of the potential led to the formation of VO2+ ions. The surface oxygen was involved in both pathways. For the binder phase, the V(IV) to V(V) conversion went through the direct formation of pure VO2+ ions and required a higher overpotential to initialize the process.
In summary, we were able to provide clear evidence of dimers incorporation into the electrochemical reactions of catholyte in VFB on the oxidized surfaces and get insights into the surface modification role for the utilize electrode material. Therefore, this new spectroelectrochemical method is a useful tool to track species transformation during the redox reactions occurring at interfaces.
Magnetic Chemistry and Its Possible Applications in Analytical Spectroscopy and Related Fields
Authors: Burns Matthew 
Published: July 2021

Developments in chemistry have stemmed from applying principles from other fields that develops into a field itself. Magnetism applied to chemistry - Magnetic chemistry is one of them. Taking electrochemistry that uses an electric field/current inducing a reaction that doesn’t occur in natural conditions; magnetic chemistry uses a magnetic field inducing conditions and possibly reactions.
Three areas are discussed; principles involved, results from using a magnetic field on hydrocarbon fuels, and possible implements in analytical spectroscopy. Starting on how Faraday’s Induction Law is used in altering compound properties. Then, discussing paramagnetism/diamagnetism of atoms/compounds emphasizing diamagnetic compounds, then on intermolecular forces emphasizing on cohesive forces and pseudo structures formed (“clustering”) then discussing quantum principles - emphasizing electron coupling interactions focusing on angular momenta, spin-orbit interaction, and Zeeman Effect.
Then, showing results of how applying a magnetic field alters hydrocarbon fuels properties. Explaining how it reduces the “clustering” of molecules, surface tension, viscosity, pollution and increasing volatility and efficiency. Then explaining how an applied field affects the molecules emphasizing on how increasing field strength increases affects and mentioning on how it actually enhances infrared and UV-Vis spectra.
Then discussing how the results can be applied to analytical spectroscopy. The increased volatility can improve atomization/nebulization for ICP and GC, thus more target compounds analyzed with less waste reducing need for derivatizing agents. Spectra enhancement for spectra signals that are very weak in infrared and UV-Vis spectroscopy. Reducing mobile phase surface tension/viscosity thus conditions (flow rate, etc.) better adjusted for HPLC. Then showing how a NMR field can be used to do this.
Concluding, magnetic chemistry can be utilized to change properties/conditions of compounds and possibly induce reactions. By discussing underlying principles involved; Induction Law, paramagnetism, diamagnetism, intermolecular forces, and quantum principles, explaining how it occurs and results on applying a magnetic field to hydrocarbon fuels which has possible uses in analytical spectroscopy.
Photochemically-Induced Phase Segregation of Mixed Halide Perovskite Solar Cells
Authors: Stevenson Keith J , Luchkin Sergey 
Published: July 2021

The emerging low cost perovskite solar cell quickly reached power conversion efficiency (PCE) parity with crystalline Si solar cells [1]. Optional bandgap tuning of the perovskites by partial substitution of I- with Br- expand their application to tandem solar cells and LEDs. The only critical issue remaining to solve is their poor long term stability under operational conditions, specifically photochemical degradation by splitting into I- and Br- rich phases. Sufficient suppression of this process requires a thorough understanding of the underlying phenomena. Here we report the detailed investigation of the photoinduced phase transformation in stoichiometric and non-stoichiometric mixed halide CsPbI3-xBrx. Using in-situ Atomic Force Microscopy, we visualized real-time kinetics of halide phase segregation under illumination. The I-rich phase segregated predominantly along grain boundaries while the grain bulk remained enriched with Br. It was proposed that photogenerated Pb0 and I3
- species are selectively expelled from grain bulk into grain boundary resulting in the phase splitting. This work supports our focus in understanding degradation mechanisms in perovskite materials for next generation solar cells [2-3].
[1] Best Research-Cell Efficiency Chart | Photovoltaic Research | NREL, (n.d.). https://www.nrel.gov/pv/cell-efficiency.html (accessed October 12, 2019).
[2] Akbulatov, A.; Frolova, L.; Dremova, N.; Zhidkov, I.; Martynenko, V.; Tsarev, S.; Luchkin, S.; Kurmaev, E.; Aldoshin, S.; Stevenson, K. J.; Troshin, P. “Light or Heat: What Is Killing Lead Halide Perovskites Under Solar Cell Operation Conditions?," J. Phys. Chem. Lett.
2020, 11(1), 333-339.
[3] Frolova, L. A.; Luchkin, S. Yu; Akbulatov, A. F.; Dremova, N. N.; Stevenson, K. J.; Troshin, P. A. “Efficient and Stable All-Inorganic Perovskite Solar Cells Based on Nonstoichiometric CsxPbI2Brx (x>1) Alloy,” J. Mater. Chem. A
2019
, 7(18), 5314-5323.
Versatile Nanosensor Probes for the Detection of Ionic Neurotransmitters at Biological Nanostructures
Authors: Shen Mei 
Published: July 2021

The Nano-Interface between Two Immiscible Electrolyte Solutions (ITIES) provides a unique analytical platform for the study of ionic species of biological interest such as neurotransmitters on living bio-structures. A typical nano-ITIES consists of a laser pulled quartz pipette with an orifice in the few nm range that can be filled with an immiscible organic solution for its immersion into biologically-relevant fluids, thus forming a liquid/liquid interface. Upon electrochemical polarization, charged neurotransmitters of interest can be transferred from one phase to another, which is the basis for quantitative ionic species sensing. This is particularly useful for the detection of non-redox active neurotransmitters, especially those whose detection on carbon microelectrodes is challenging. Nano-ITIES probes thus possess significant advantages over the state of the art carbon microelectrodes, which need to be enzymatically modified, for the detection of neurotransmitters such as acetylcholine. In addition, nanopipette based sensor probes have significantly improved spatial resolution compared to microelectrode.
We have developed nanoITIES electrodes to detect and quantify non-redox-active neurotransmitters, i.e., acetylcholine and gamma-Aminobutyric acid (GABA), and redox-active neurotransmitters (1-4). We further demonstrated its capability for in situ sensing of cholinergic transmitters released from living neuronal structures (5, 6). Recently, we introduced a novel ionophore with multiple binding centers, tris(crown ether), in the assisted ion transfer of various metal ions and dopamine; comparative studies were made between tris(crown ether) and mono(crown ether) (7). Solvent, as part of ITIES structure, plays critical roles in electrochemical reactions at ITIES; we further explored new types of solvent for the ITIES field (8). Here, I present recent development from my group for detecting various ionic species, including neurotransmitters.
Acknowledgement: The research presented here was supported by the National Institutes of Health under Award Number R21NS085665 and the National Science Foundation under a CAREER award (CHE 19-45274) to M. Shen. We would like to thank our collaborators, Sweedler and Moore Groups.

Anal. Chem., 2015, 87, 5095-5100.

Analytical Methods, 2015, 7, 7095-7105.

J. Electrochem. Soc., 2016, 163, H3072-H3076.

Anal. Chem., 2018, 90, 3067-3072.

J. Am. Chem. Soc., 2018, 140, 7764-7768.

Chem. Sci., 2018, 9, 4937-4941.

ChemElectroChem., 2020, 7, 967-974.

Electrochimica Acta, 2020, 357,136788.
Discrete Charges at ITIES - Polarisation and Electrochemical Reactions
Authors: Gschwend Grégoire , Olaya Astrid , Girault Hubert 
Published: July 2021

The role of the discreteness of the charges at ITIES has recently been revisited within the framework of the so-called "Discrete Helmholtz" model. The main conclusion of this model is that the potential drop across an ITIES takes place over a bilayer of correlated ions rather than across two back-to-back diffuse layers as suggested by the Gouy Chapman approach. The experimental signatures from Surface Second Harmonic Generation (SSHG) and electrocapillary measurements are a constant capacitance and a linear relationship between surface charges and applied potential. We shall here discuss polarisation at ITIES and compare the different models. We shall also discuss how the interfacial polarisation acts as a driving force for potential dependant electrochemical reactions such as ion transfer and electron transfer.
In the second part of the presentation, we shall discuss water splitting reactions at ITIES using redox photo-electrocatalysis. We shall discuss the different reactions leading to hydrogen evolution and present some very recent data on oxygen evolution.
Finally, we shall discuss the feasibility of batch water splitting at ITIES as an industrial process.

Figure 1
Probing the Oxidative Doping of Single Polymer Nanoparticles
Authors: Amin Hatem M.A. , Attia Mina , Tschulik Kristina 
Published: July 2021

Due to their diversity of applications in research and industry, nanomaterials have gained a great technological importance in the last two decades. Among others, polymeric nanoparticles (NPs) attract a special interest in polymer batteries and solar cells.[1,2] Charge transfer is the main process underlying the charging/doping of polymer NPs.[2] This process involves uptake and release of ions from the polymer and has typically been studied using the ensemble method, that is by immobilizing a large number of these particles on an electrode and measuring the resulting charge/discharge response. Understanding the underlying process steps using ensemble studies is difficult, since charge transfer and mass transport processes are overlapping and thus can only be estimated. In addition, the ensemble method can be misleading since particles often agglomerate on the electrode so that only a fraction of their surface is accessible. Thus, probing the intrinsic response at the single particle level is necessary to understand, for instance, the charging process and ion intercalation capacity in rechargeable polymer batteries. This can be achieved, by single nanoparticle impact electrochemistry.[3-5]
Herein we demonstrate how quantifying the charging/doping of single particles of industrially important polymers can be achieved using this “nano impact” method. The polymeric NPs were successfully synthesized and characterized using UV-Vis, FTIR, DLS and SEM. For comparison, the doping behavior of ensembles of the NPs was investigated using cyclic voltammetry. Furthermore, the effect of dopant on the doping kinetics was studied. By linking the nano impact results with independent sizing data, it can be revealed whether the entire particle is doped, or a sort of core-shell structure is made. Importantly, the intrinsic kinetics of the doping of single NPs are investigated and the rate determining step in the doping process is determined. This work adds new insights into the charging of conducting polymers at the single particle scale which is expected to have a significant impact on emerging applications such as polymer batteries and supercapacitors.
Literature:
[1] Electrically Conducting Polymers: An Emerging Technology, Bakhshi, A. K.; Pooja Rattan. Current Science, 1997, 73, 648–651.
[2] Electrochemically Active Polymers for Rechargeable Batteries, Novák, P; Müller, K; Santhanam, K.S.V.; Haas, O. Chem. Rev. 1997, 97, 207-281
[3] Electrode-particle impacts: a users guide, Sokolov, S. V.; Eloul, S.; Kätelhön, E.; Batchelor-McAuley, C.; Compton, R. G. Physical chemistry chemical physics: PCCP 2016, 19, 28–43.
[4] Electrochemistry at single bimetallic nanoparticles - using nano impacts for sizing and compositional analysis of individual AgAu alloy nanoparticles, Saw, E. N.; Grasmik, V.; Rurainsky, C.; Epple, M.; Tschulik, K. Faraday discussions 2016, 193, 327–338.
[5] Doping of single polymeric nanoparticles, Zhou, X.-F.; Cheng, W.; Compton, R. G. Angewandte Chemie (International ed. in English) 2014, 53, 12587–12589.
Separating and filtering compound mixtures using a magnetic field
Authors: Burns Matthew 
Published: July 2021

Currently there is research in using magnetic fields to produce reactions and altering properties of compounds. This research has given promising results such as using a magnetic field to improve hydrocarbon fuel combustion. Results have shown better fuel efficiency and exhaust emissions reduction by using a magnetic field of varying strengths. This research has shown that other compound properties such as viscosity, surface tension, boiling point, can be altered with a sufficiently strength magnetic field. It has even been shown that IR and UV spectra can be enhanced by a magnetic field. Here the discussion will focus on showing potential magnetic field use in the separation sciences - stating the current research and developments of using magnetic filtering in separating compounds.
Separation science deals with using mobile and stationary phases to separate compound mixtures in HPLC and GC. Factors such as flow rate, temperature, stationary phase particle size, and mobile phase solvent play key roles in separation. Other methods such as electrophoresis and dialysis use techniques similar to HPLC and GC. Here will be shown the potential of how a magnetic field can used separating compounds; organic and bioorganic including proteins, viruses, and even bacteria. First briefly discussing magnetic/electric fields and on organic and bioorganic compounds emphasizing on nucleophilic/electrophilic compounds, proteins, nucleotides, and microorganisms. Continued with examples of the research on using magnetic fields to filter and/or separate compounds and solution mixtures of aqueous/nonaqueous nature emphasizing on the research in oil spill clean-ups, blood dialysis and space applications.
From what was presented, it will be shown how this research can be applied to four main areas. In electrophoresis, it will show the advantages of a magnetic field over the electric one. The removing of deadly diseases such as the coronavirus and wastes from blood using magnetic dialysis. The use in sample preparation methods. For HPLC/GC separations focus will be on magnetic separation enhancement and advantages of a proposed magnetic stationary phases over the current ones.
The potential of magnetic field use in the separation sciences is great. Based on previous research such as improving fuel combustion has shown practical potential in other areas such mixture separations. By discussing the principals involved in this shows how it is achieved. The potential feasibility in improving electrophoresis, dialysis, and HPLC/GC separations can help reduce costs and preparation time.
Bipolar Membranes with Systematically Varied Interfacial Areas in the Junction Region
Authors: Kole Subarna , Arges Christopher G. 
Published: July 2021

Bipolar membranes (BPMs) have been historically deployed in electrodialysis for pH adjustment of process streams and the production of acids and bases. More recently, it has seen increasing popularity for fuel cell and electrolysis technologies. Under reverse bias, BPMs allow for disparate pH control in electrochemical cells and regeneration of electrolyte. The ability to maintain disparate pH in the cell expands the palette of electrocatalysts for a given cell configuration. Despite the enticing potential BPM electrolyte separators offer, they often cannot facilitate large current density values normally attained with single-ion conducting membranes (i.e., CEM or AEMs) in fuel cells and electrolyzers. This challenge has motivated three general strategies to improve the performance of BPMs: i.) judicious selection of the water-dissociation catalyst in the junction region; ii.) facilitating improved water transport to the junction region; and iii.) fabricating high surface area interfaces between the AEM and CEM in the junction region.
This talk presents soft-lithography as a method to generate micropatterned membrane surfaces with a defined interfacial area that is retained during BPM fabrication. The approach is conducive for a variety of commercially available CEM and AEM chemistries (e.g., Nafion, perfluorinated AEM, Orion poly(arylene) AEM, and SPEEK). These chemistries are stable at elevated temperatures, extreme pHs, and in the presence of strong oxidizers. Our work demonstrates a 250 mV in the on-set potential for water-splitting while also increasing the current density by 15% when increasing the interfacial area by 2.28x. The improved water-splitting observations are primarily explained by calculating the electric field in the junction region using the Poisson equation. The marginal increase in current density was attributed to the BPM being under mixed reaction-diffusion control. Finally, we demonstrate a block copolymer lithography approach for generating nanopatterned surfaces on ion-exchange membranes. Taking advantage of the tunability of block copolymer lithography, the feature sizes and geometry of the nanostructure at the interface can be systematically controlled.
This work was supported from NSF Award # 1703307.

Figure 1
Unveiling the Active Structure of Single Nickel Atom Catalyst for Electrochemical CO2 Reduction
Authors: Liu Yuanyue , Zhao Xunhua 
Published: July 2021

A single nickel atom embedded in graphene is one of the most representative single-atom catalysts, and it has a high activity and selectivity for electrochemical CO2 reduction (CO2R) to CO. However, the catalytic origin, especially the coordination structure of Ni, remains highly puzzling, as previous density functional theory (DFT) calculations showed that all the possible structures should be inactive and/or nonselective. Here, using ab initio molecular dynamics (AIMD) and a “slow-growth” sampling approach to evaluate the reaction kinetic barriers, we show that the charge capacity (of the site) and hydrogen bonding (with the intermediates), which were neglected/oversimplified in previous DFT calculations, play crucial roles, and including their effects can resolve the catalytic origin. Particularly, a high charge capacity allows the catalytic site to carry more charges than required for the electrochemical step, lowering the electrochemical barrier, and hydrogen bonding promotes the reaction that produces polar intermediates by stabilizing the intermediates and facilitating the H transfer from water, explaining the high selectivity for CO2R over the hydrogen evolution reaction. Consequently, we find that a hybrid coordination environment (with one nitrogen and three carbon atoms) for the Ni-atom is most active and selective for CO2R. Our work not only explains a long-standing puzzle for an important catalyst but also highlights the crucial roles of charge capacity and hydrogen bonding, which can help elucidate the mechanisms of other heterogeneous electrocatalysts in aqueous solution and enable more effective catalyst design [1,2].
[1] X. Zhao, Y. Liu, J. Am. Chem. Soc. 2020, DOI: 10.1021/jacs.9b13872
[2] D. Kim, J. Shi, Y. Liu, J. Am. Chem. Soc., 2018, 140, 9127-9131
Primary Vs. Secondary Alcohols Electrooxidation: Mechanistic Insights
Authors: Mangoufis-Giasin Iosif , Khanipour Peyman , Piqué Oriol , Mayrhofer Karl J. J. , Calle-Vallejo Federico , Katsounaros Ioannis 
Published: July 2021

Direct Alcohol Fuel Cells (DAFCs), mostly based on methanol or ethanol, have been in the spotlight in the past, due to alcohols’ high and easy availability, low cost, liquid form, low temperature operation and comparable theoretical mass energy densities in comparison with Hydrogen Fuel Cells.[1] However, 2-propanol fuel cells can be preferred for coupling with Liquid Organic Hydrogen Carriers (LOHCs), by creating a closed loop where 2-propanol is oxidized in a fuel cell to acetone and the latter is hydrogenated back to 2-propanol by the catalytic transfer hydrogenation reaction with a hydrogen-rich LOHC molecule.[2]

Here, we characterize the products of 2-propanol oxidation on Pt and PtRu and find that the reaction is selective to acetone on both surfaces. Interestingly, the addition of ruthenium gives rise to an early oxidation peak close to the reversible potential, which is not present in 1-propanol oxidation.[3] The early onset of the 2-propanol oxidation leads to significantly larger Open Circuit Voltages (OCVs) for fuel cells based on 2-propanol compared to 1-propanol, when PtRu is used as the anode. By studying the oxidation of larger (C4 and C5) alcohols, we find that this is a unique characteristic of secondary alcohols on platinum-ruthenium bimetallic catalysts. Using a combination of Rotating Disc Electrode (RDE) measurements, Density Functional Theory (DFT) calculations and real-time product analysis with Electrochemical Real-Time Mass Spectrometry (EC-RTMS) we conclude that the unique feature of secondary alcohols stems from the difficulty in breaking their C-C bond, which prevents their dissociative adsorption at low potential and enables the optimal adsorption on platinum-ruthenium ensemble sites.[4]

Acknowledgements

I.M.-G, P.K, K.J.J.M. and I.K. acknowledge financial support by the Bavarian Ministry of Economic Affairs, Regional Development and Energy.
F.C.-V. acknowledges funding from Spanish MICIUN RTI2018-095460-B-I00, Ramón y Cajal RyC-2015-18996 and María de Maeztu MDM-2017-0767 grants and partly by Generalitat de Catalunya 2017SGR13. O.P. thanks the Spanish MICIUN for a PhD grant (PRE2018-083811). We thank Red Española de Supercomputación (RES) for supercomputing time at SCAYLE (projects QS-2019-3-0018, QS-2019-2-0023, and QCM-2019-1-0034), MareNostrum (project QS-2020-1-0012), and CENITS (project QS-2020-2-0021). The use of supercomputing facilities at SURFsara was sponsored by NWO Physical Sciences, with financial support by NWO.

References

[1] C. Lamy, Encyclopedia of Applied Electrochemistry, 2014, 321-330.
[2] G. Sievi et al., Energy and Environmental Science, 2019, 12(7), 2305-2314.
[3] P. Khanipour et al., ACS Applied Materials & Interfaces, 2020, 12, 33670-33678.
[4] P. Khanipour et al., Angewandte Chemie International Edition, 2019, 58(22), 7273-7277.