bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Detecting Macromolecular Configurational Transformations Using Sound Velocity
Authors: Parkinson Graham Dalton Baker , Blake Alyssa M , Russo Paul S
Published: July 2021

Macromolecules are dynamic, flexible, and able to undergo conformational changes in response to their local environments. Many of these transformations are paramount within biological systems. Numerous techniques exist for detection of these states including NMR, SAXS, and optical methods including circular dichroism or optical rotation. These techniques are not without their challenges. Many can be quite involved, require advanced sample preparation, and are easily confounded with the presence of additional components. Here we present a facile route to detection of these conformational transitions using sound velocity within macromolecular solutions. The first test case involves the polymer poly(ε-carbobenzyloxy-l-lysine), PCBL, which has long been known to exhibit an inverse coil-to-helix transition at ∼27 °C when dispersed in the optically clear but UV-opaque m-cresol solvent. We then look to extend this further into other solvents, especially aqueous systems. Sound velocity proves effective at sensing many of these conformational transitions when compared with traditional methods as well as offering a promise on a variety of real world systems.
(Invited) Photoelectrode Materials Design for Solar Fuels: Where Are We Now?
Authors: Rajeshwar Krishnan
Published: July 2021

Solar water splitting offers an attractive solution for renewable energy storage. Ternary metal vanadates have drawn attention for use in photoelectrochemical (PEC) water oxidation due to their low band gap and photostability.1 For example, Cu2V2O7 with a ratio of CuO: V2O5 stoichiometry (2:1) is a visible light active n-type semiconductor with a low band gap (see below), and has seen use in PEC devices because of its high stability for PEC water oxidation.2

This paper describes the development of a hybrid electrochemical/thermal route for the preparation of metal vanadate thin films. Electrodeposition is a facile, low temperature method which can be deployed to prepare thin films of a target semiconductor. Also, the optoelectronic parameters (e.g., photocurrent, flat band potential) of the thin film semiconductors prepared by electrodeposition can be measured easily without any more processing steps. In addition, the thickness of a given thin film semiconductor, a crucial factor for PEC reactions, can be controlled easily in an electrodeposition process.

A two-step electrodeposition strategy for ternary oxides3 was deployed in this study. Results will be presented for M-V-O ternary films (e.g., Cu2V2O7) on fluorine doped tin oxide (FTO) substrate. In the first step, a copper thin film was deposited cathodically from copper(II) nitrate in a non-aqueous medium to preclude copper oxide formation. In the second step, the copper thin film was stripped anodically in ammonium metavanadate (NH4VO3) aqueous solution to generate Cu+ and subsequent in situ precipitation with VO3
- species to yield a green CuVO3 film on the substrate. Electrochemical quartz crystal microgravimetry confirmed two- and one-electron stoichiometry for the first and second steps respectively.

Finally, aspects related to film stability and charge transfer efficiency as they relates to solar water splitting, will be reviewed in the light of data from our group.

References:

K. Rajeshwar, M. K. Hossain, R. T. Macaluso, C. Janáky, A. Varga, P. J. Kulesza, J. Electrochem. Soc.
2018, 165, H3192−H3206.

M. K. Hossain, P. Sotelo, H. P. Sarker, M. T. Galante, A. Kormányos, C. Longo, R. T. Macaluso, M. N. Huda, C. Janáky, K. Rajeshwar, ACS Appl. Energy Mater.
2019, 4, 2837-2847.

L. H. Antonia, N. R. de Tacconi, W. Chanmanee, H. Timmaji, N. Myung, K. Rajeshwar, Electrochem. Solid-State Lett.
2010, 13, D29-D32.
(Allen J. Bard Award) Electrochemistry of Platinum: New Views on an Old Problem
Authors: Koper Marc
Published: July 2021

Platinum is the most used electrocatalyst in electrochemical energy conversion devices such as fuel cells and electrolysers. In this talk I will highlight the recent work of my group on understanding the surface chemistry of platinum in an aqueous electrolyte, by combining single-crystal electrochemistry, density functional theory calculations, ultra-high-vacuum modeling, in situ spectroscopy and in situ electrochemical scanning tunneling microscopy. I will challenge some existing explanations and interpretations of platinum electrochemistry, and show the sometimes surprising surface disordering of platinum that happens at both positive (anodic) and negative (cathodic) potentials.
(Invited) Understanding Inner-Sphere Electrochemical Reactions at the Molecular Level
Authors: Jackson Megan , Pegis Michael , Kaminsky Corey , Surendranath Yogesh
Published: July 2021

Interfacial ET processes can be broadly classified as either outer-sphere or inner-sphere. For outer-sphere reactions, the electrode serves only as a chemically inert source or sink of electrons, whereas, for inner-sphere reactions, ET accompanies bond rearrangement at the electrode surface. While outer-sphere ET is well-described by Marcus-type models, there currently exists no analogous molecular-level understanding of inner-sphere ET at electrode surfaces, despite the central role of these reactions in virtually all electrochemical technologies, ranging from supercapacitors to batteries to fuel cells and electrolyzers. This persistent knowledge gap results from the inability to characterize or control the chemistry of metallic electrode surfaces at the molecular level, making it difficult, if not impossible, to unambiguously correlate the thermodynamics and kinetics of inner-sphere reactions to the local structure of the surface site undergoing bond rearrangement. This talk will highlight a strategy developed in our group for conjugating well-defined molecular active sites to graphitic electrodes. Electrochemical and spectroscopic data indicate that these graphite-conjugated molecules do not behave like their solution-phase analogues, but rather as metallic active sites that proceed exclusively through inner-sphere ET reaction mechanisms. This new class of functional interfaces enables investigations of inner-sphere interfacial ET with an unprecedented level of detail.
(Invited) A Systems View of Solar Energy Conversion Efficiency in Dye-Sensitized Photoanodes
Authors: Houle Frances
Published: July 2021

Dye-sensitized photoelectrodes are highly complex structures, involving large internal surface areas hosting tightly coupled interfacial and electrolyte chemistry. How the electrode architecture and the chemical reactions in them are connected to measured photovoltages and photocurrents for the simplest case of the dye-sensitized solar cell is examined using full-system multiscale reaction-diffusion simulations. These calculations provide a fully spatially resolved time history of the system, spanning nm-microns and ns-sec. In this talk, a basic but physically realistic computational framework will be introduced, and several aspects of system behaviors revealed by the simulations will be described. The influence of molecular diffusion on photocurrents, within the photoelectrode and across the system, will be described. Whether electron-electrolyte recombination within the photoanode is responsible for losses that limit efficiency is also examined. Recombination reactions are found to be significant, but are not performance-limiting because the reactions drive shifts in the electrolyte chemistry to support efficient dye cycling, and compensate for losses. This phenomenon can compensate for efficiency limitations due to diffusion between the photoanode and the cathode. The implications of these findings for strategies to improve the efficiency of this class of systems are discussed.
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.
Electrochemical Reduction of Nitrogen to Ammonia at Ambient Conditions Using 2D Metal-Organic Frameworks
Authors: Hassan Mohamed H. , Andreescu Emanuela
Published: July 2021

The conversion of N2 into ammonia is one of the most important processes in the chemical industry and the basis to produce fertilizers necessary to maintain agricultural food production. The conventional Haber-Bosch process requires high energy input (1% of world energy supply) and suffers from harsh reaction conditions with an associated CO2 emission as a side product. More sustainable alternatives for ammonia synthesis are thus needed to sustain the growing demand. Electrochemical reduction of N2 (NRR) is an attractive approach that utilizes catalysts that can selectively favor one reduction product over the others at a lower reduction potential. Despite the unprecedented efforts in utilizing metal-organic frameworks (MOFs) in the electrocatalytic N2 reduction, their high electrical resistance, poor product selectivity and low stability limits their use in some catalytic applications. This study is describing a facile one-pot synthesis method that can modulate the MOF’s conductivity via growing 2D ultrathin copper/palladium-tetrakis (4-carboxyphenyl) porphyrin Cu(PdTCPP) nanosheets blended with graphene giving Cu(PdTCPP)@G. This method favors the formation of free-standing MOF/graphene composite. The electrostatic interaction between the MOF and the graphene sheets allows direct electron transfer through the MOF matrix enabling them to become electrically accessible. Palladium is employed as the main catalytic site for NRR that offers high activity and selectivity giving NH3 yield rate of 5.45 µg h-1 mg-1 MOF (52 µg h-1 mg-1 Pd) at -0.091 V vs RHE and a Faradaic efficiency of 8.45% in 0.1 M phosphate buffer. This material also showed a promising photocurrent generation making it attractive for further development of a photocatalytic NRR that can run under sunlight, with potential to become fully sustainable.
Tantalum Nitride As a Promising Catalyst for Hydrogen Evolution Reaction
Authors: Abghoui Younes , Skulason Egill
Published: July 2021

Stable and active catalyst material among transition-metal nitrides (TMNs) have been investigated via density functional theory (DFT) calculations for possibility of catalysing the hydrogen evolution reaction (HER). The result from DFT modelling revealed that a full monolayer of proton was formed on the (100) facet of the rocksalt structure of TaN surface. The H coverage as a function of applied potential was calculated on the surface too. Activation energy of H2 formation was also calculated at varying applied potentials. The rate of the reaction was calculated and compared with that of Pt(111). The results nominated TaN capable of catalysing HER at low overpotentials of around −0.1 V vs. a reversible hydrogen electrode, with a similar activation energy for proton recombination from the surface to make H2 as that reported for Pt(111). In addition, TaN was predicted to function as good as MoS2 with regards to activity. This is interesting result that can motivate experimentalists to test this material further for the possibility of its real-life applications.
Nickel(II) Bis(diethyldithiocarbamate) As a Redox Mediator in Dye Sensitized Solar Cells
Authors: Dalpati Niharika , Farnum Byron H.
Published: July 2021

Since the first report of a dye sensitized solar cell (DSSC) in 1991, the 2e- redox cycle of triiodide/iodide served as the archetype for redox mediators. However, major shortcomings of I3
-/I- include corrosion with metal surfaces and its redox potential of ERedox = -0.34 V vs Fc+/0, which limits the maximum photovoltage to ~0.8 V. Increasing ERedox using alternative mediators has been a primary research focus. Although [CoIII/II(bpy)3]3+/2+ and its derivatives have been shown to possess more positive ERedox values, these mediators suffer from slow electron transfer kinetics. Here we present the combination of a multielectron redox cycle with a tunable transition metal complex which could provide the best solution for increasing ERedox while maintaining a 2e- redox cycle. This research focuses on using [NiIV(dtc)3]+/NiII(dtc)2 as a redox mediator in DSSCs where dtc- is a bidentate dithiocarbamate ligand, which undergoes 2e- oxidation from Ni(II) to Ni(IV) during dye regeneration. Steady state photoluminescence quenching of [Ru(bpy)3]2+ shows comparable behavior between Ni(dtc)2 and iodide with a Ksv = 1.72×10-9 M-1 for Ni(dtc)2 compared with 3.67×10-9 M-1 for I-. Photoelectrochemical measurements were made using FTO/TiO2 electrodes sensitized with the N3 dye in the presence of I- or Ni(dtc)2. Cyclic voltammetry experiments were carried out using a 0.001 M Ni(dtc)2 with external light source (white light LED) with different light intensities ranging from 0 to 125 mW/cm2. Similar currents were obtained in the case of Ni(dtc)2 compared to iodide for all measured light intensities. The measured open-circuit potential was also found to be larger in case of Ni(dtc)2, consistent with the ERedox = 0.01 V for the Ni(IV/II) couple. This value is 0.32 V larger than I3
-/I- and could produce a theoretical photovoltage value of 1.15 V which is 0.14 V more than the maximum value reported so far with a cobalt based mediator. These studies show that [NiIV(dtc)3]+/Ni(dtc)2 has the potential to serve as an alternative redox mediator to I3
-/I-.
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
Investigation of Hydrogen Interaction (Electrosorption and Evolution) with Si in Hydrogen Fluoride Electrolyte
Authors: Priyadarshani Divya , Neergat Manoj , Kottantharayil Anil
Published: July 2021

Metallization of silicon is important to make electrical contacts. Thus, copper (Cu), nickel (Ni) etc. are deposited on Si by various methods including electrochemical and photo-electrochemical methods. Nature of the electrochemical processes of Si with the electrolytes at relevant potentials decides the success of metallization. Thus, it is important to investigate the interaction of electrolyte with Si at cathodic overpotentials. Therefore, n-type and p-type Si of different doping concentrations are investigated in 1% HF electrolyte at cathodic overpotentials. Hydrogen evolution reaction (HER) is expected at very high cathodic overpotentials but very interesting processes occur at intermediate overpotentials. Therefore, the Si/electrolyte interface is investigated using voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Mott-Schottky (MS) analysis. At very high concentration of the dopants, metal-like features are observed with Si. There are very good correlations between dopant concentration, overpotentials, and flat -band potential and inductive behavior of the semi-conductor.

Figure. EIS recorded on n-Si at different cathodic overpotentials in 1% HF (a) 4-7 Ωcm (b) 0.00-0.005 Ωcm. The corresponding Bode plots are shown in (d) and (f), respectively.

Figure 1
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
Use of Aditive Manufacturing for Electrocatalyst Fabrication for Oxygen Reduction Reaction
Authors: Zamora-Suárez Andrés , López-González Berenice , Herrera-Celis José Luis , Perez Bueno Jose De Jesus , Cuevas-Muniz Francisco Mherande
Published: July 2021

3D printers can be versatile and can be used in the design of monolithic or complex geometry energy systems. However, the biggest challenge is the development of materials that can be used as electrode surfaces. In this work, the results of electrodeposition of platinum over a ABS 3d printed surface are presented. Commercial conductive ABS was used for this purpose. In addition, some mixtures were prepared by mixing the ABS with vulcan carbon, the conductivity was measured by Kelvin sensing, obtaining 0.25 S/cm at 25% vulcan carbon, in constrast with 1.54x10-3 S/cm for commercial ABS, however this material becomes fragile and difficult to extrude. Electrodeposition was performed from H2PtCl4 in acidic media. SEM studies shown a homogeneous distribution of the platinum particles (circa 1 micron) in all the surface of the commercial ABS. After 1 minute of electrodeposition, the electroactive area is 10 times lesser than the obtained in a glassy carbon electrode. The electric resistance it is the main cause of this, however, it is a first aproximation to get electrodeposit in a ABS conductive material, and the horizon is promising for energy applications.
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
Organic Compounds Improving the HER/HOR Kinetics of Pt in Alkaline By Reorienting Interfacial Water
Authors: Sun Qiang , Mukerjee Sanjeev , Jia Qingying
Published: July 2021

Hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) are fundamentally and practically important in electrochemistry. However, the sluggish kinetics of HER/HOR in alkaline solution remains ambiguous and has been under extensive debate1. Most recently, Snyder’s and Tang’s groups2 reported that caffeine can significantly enhance both the HER and HOR kinetics of all Pt surfaces in alkaline solutions. However, the underlying mechanism for the caffeine-induced HER/HOR improvement of Pt in alkaline remains unexplained. In this work, we tend to resolve this puzzle by modulating the HER/HOR kinetics of Pt in alkaline by adding a variety of organic compounds in alkaline solutions, and probing how these organic compounds react with the Pt surface and tune the interfacial environment via advanced electrochemical characterizations and in situ spectroscopic techniques. We found that the organic compounds are non-specifically adsorbed on the Pt surface during the HER/HOR, and thus their induced HER/HOR improvement of Pt in alkaline cannot be accounted for by the hydrogen binding energy theory and bifunctional mechanism. We alternatively argue that the organic compounds improve the HER/HOR kinetics of Pt in alkaline by reorienting the interfacial water to facilitate the Volmer step, which refines our previous argument that interfacial water improves the HER/HOR kinetics of Pt via shuffling the reaction intermediates such as Had and OHad throughout the interface3.

Acknowledgement

This work was supported by the Office of Naval Research (ONR) under award number N00014-18-1-2155. This research used beamline 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Liu, E.; Li, J.; Jiao, L.; Doan, H. T. T.; Liu, Z.; Zhao, Z.; Huang, Y.; Abraham, K. M.; Mukerjee, S.; Jia, Q., Journal of the American Chemical Society
2019,
141 (7), 3232.

Intikhab, S.; Rebollar, L.; Li, Y.; Pai, R.; Kalra, V.; Tang, M. H.; Snyder, J. D., ACS Catalysis
2020,
10 (12), 6798.

Liu, E.; Jiao, L.; Li, J.; Stracensky, T.; Sun, Q.; Mukerjee, S.; Jia, Q., Energy & Environmental Science
2020,
13 (9), 3064.
Electrocatalytic Formation of C-C Bonds in Phenolic Compounds
Authors: Martic Sanela
Published: July 2021

Electrocatalytic transformations giving rise to new C-C bond formation and new products is of value. We have recently discovered that phenolic compounds undergo selective electrochemical oxidation giving rise to reactive phenoxyl radicals which combine to produce a product with new C-C bond formed [1]. Five phenolic compounds including butylated hydroxytoluene (BHT), 4-tert-butylphenol (4TBP), 2-tert-butylphenol (2TBP), 2,4,6-tri-tert-butylphenol (TTBP), and 2,6,-di-tert-butylphenol (DTBP) were systematically evaluated by electrochemical methods to determine their oxidation/reduction potentials as a function of concentration. At identical experimental conditions, only DTBP exhibited electrochromic behavior which was dependent on concentration and electrochemical cycling. The electrocatalytic oxidation of DTBP resulted in a formation of a new compounds due to C-C coupling. The reaction was monitored by electrochemical methods, UV-vis spectroscopy and final product characterized by X-ray diffraction. Recently, we expanded the electrocatalysis to include diverse phenolics such as dihydroxybiphenol (DHBP) which also formed a yellow-coloured solution, indicating a product formation. The electrochemical and spectroscopic characterization of DHBP reaction will be described.

References

Zabik, N., Virca, C. N., McCormick, T., Martic-Milne, S. (2016). Selective electrochemical versus chemical oxidation of bulky phenols. J. Phys. Chem. B. 120: 8914-8924.
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.
Online Stability Investigations of Platinum Electrodes in Nonaqueous Media
Authors: Ranninger Johanna , Nikolaienko Pavlo , Mayrhofer Karl J. J. , Berkes Balázs B.
Published: July 2021

In the process of developing novel electrocatalysts, the focus mainly lies on finding highly active and selective materials. The stability of electrodes is often underestimated, even though a poor stability is inextricably related to economic losses. Fundamental understanding of electrode dissolution processes in nonaqueous media is not only crucial for applications like nonaqueous battery systems, sensors, capacitors but also for organic electrosynthesis. The reasons for electrode degradation are among others anodic dissolution, cathodic dissolution or cathodic corrosion. Enhanced knowledge of dissolution mechanisms, especially understanding the influence of factors like composition or structure of electrodes, electrolytes and temperature, is important to optimize the operation conditions of reactors, and with that limit electrode degradation and increase the lifetime of devices and improve processes.

Coupling electrochemical measurements with an inductively coupled plasma mass spectrometer (ICP-MS), allows online stability studies and gives valuable insights into degradation mechanisms of different electrodes and catalyst materials, which are relevant in various applications. We have developed an electroanalytical flow cell (EFC) coupled to an ICP-MS, which is suitable for the use in aggressive nonaqueous electrolytes. Furthermore, the EFC is operated in an argon filled glovebox, which allows otherwise unattainably strict control of experimental conditions, like the water content of electrolytes [1,2].

In order to demonstrate the capabilities of this novel method, dissolution of platinum as an ideal model system will be depicted first: this metal has excellent electrocatalytic activity and somewhat falsely supposed inertness. It is widely used in various fields of applications and its behavior in aqueous media is fairly well known. New aspects of its stability in different nonaqueous electrolytes are unveiled together with dependences on the chemical properties of the solvents and the conducting salts. While the dissolution behavior of completely water-free protic and aprotic electrolytes is very similar, the dissolution behavior changes markedly upon temperature variation or in presence of trace amounts of water.

Different platinum dissolution profiles in several nonaqueous electrolytes will be discussed and dissolution mechanisms will be proposed, based on studies with changing water content. The dissolution of this electrode material has been followed during a running electrosynthesis. The correlation of possible reaction intermediates with the stability will be illustrated for a Kolbe electrolysis.

Literature:

[1] J. Ranninger, et al., Electrochem. Comm., 2020, 114 (106702),

[2] J. Ranninger, et al., J. Electrochem. Soc., 2020, 167 (121507)
Computational Guidance in Electrocatalysis – The Hydrogen Evolution Reaction As Case Study
Authors: Abghoui Younes , Skulason Egill
Published: July 2021

Electrocatalytic synthesis of high-value-added products from atmospheric elements has attracted numerous attentions in order to find a promising alternative to the centralized, energy-intensive, and CO2 emitting processes. Coupling renewable sources of energy with electrochemical reduction of these elements to chemicals, if done efficiently, could tackle the non-dispatchable nature of renewables by providing storage in chemical bonds. To realize industrial-scale electrocatalysis, substantial challenges on both the fundamental and system levels need to be addressed. On the fundamental side specially, there is a huge need for screening new materials that could be promising as active and selective catalysts. Computational modelling with density functional theory (DFT) can play a great deal by saving chemicals, instrumentation, and avoiding hazardous conditions but at the same time being reliable in finding trends, nominating potential candidates, and guiding experimentalists in the field. Here utilisation of DFT calculations for finding active catalysts for hydrogen evolution reaction (HER) which is one of the fundamental electrochemical processes is presented where new materials have been investigated for this reaction and interesting results obtained. We will talk about the catalyst selection and the model system, calculation of the energetics and activation energies toward H2 formation, predicted onset potential and the ate of the reaction.
(Keynote) Nanostructured Materials for CO2 and Oxygen Reduction
Authors: Gewirth Andrew A. , Chen Xinyi , Esposito Anne Marie
Published: July 2021

This talk addresses the reactivity associated with CO2 and O2 reduction. For CO2, electrodeposition of metals from plating baths containing 3 an inhibitor yields highly porous materials exhibiting enhanced activity for electrochemical reactions. Electrodeposition of CuAg or CuSn alloy films from such plating baths yields high surface area catalysts for the active and selective electroreduction of CO2 to multi-carbon hydrocarbons and oxygenates. Alloy films containing Sn exhibit greater efficiency for CO production relative to either Cu along or CuAg at low overpotentials. In-situ Raman and electroanalysis studies suggest the origin of the high selectivity towards C2 products to be a combined effect of the enhanced stabilization of the Cu2O overlayer and the optimal availability of the CO intermediate due to the Ag or Sn incorporated in the alloy. Sn-containing films exhibit less Cu2O relative to either the Ag-containing or neat Cu films, likely due to the increased oxophilicity of the admixed Sn. Additionally, modification of the Cu electrode with certain polymers yields substantially enhanced reactivity, due in part to control of the Cu2O layer.

For O2 reduction, we report the results of detailed magnetometry studies on non-precious metal oxygen reduction catalysts. The magnetometry clarifies uncertainties about the state of the metal in active catalysts and reports on how the catalysts change following alteration in preparation procedures, such as exposure to NH3.