bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lab-Scale X-Ray Emission/Absorption Spectroscopy for Operando Measurement of Electronic Structure of Transition Metals in Battery Electrodes
Authors: Krishnan Abiram , Mitra Samantha , Lee Dong-Chan , Alamgir Faisal M. 
Published: November 2022

Tracking the change in electronic structure of target elements is crucial to investigate the nature of redox reactions occurring in battery electrodes. X-ray emission spectroscopy (XES) and x-ray absorption fine structure (XAFS) perform this role well with high sensitivity and throughput, but the requisite of synchrotron facilities often limits those availability for material characterization.
Using a lab-scale x-ray emission/absorption spectrometer, we investigated the changes in the local structure and chemistry around the 3d transition metal elements of LiMO2 cathodes for Li-ion batteries as a function of the battery state of charge (SoC). Ex situ measurement was prepared from the electrode samples with discrete difference in SoC. Coupled with ex situ measurement, operando measurement was performed using pouch cells with LiMO2 cathode, which enabled a real-time monitoring of chemical shift in an element-specific manner resulted from changing electrode potential.
Through the XES mode of the bench-top spectrometer, fluorescence emissions from the LiMO2 cathode, or the cell containing it, was monochromatized by a spherically bent crystal analyzer (SBCA). The Kβ emissions of 3d transition metal elements such as cobalt display position/shape difference of spectrum with varying SoC. The trend of chemical shift and change in spectral features provided the information on the electronic structure variation, such as oxidation state change of 3d transition metals in LiMO2 during charge and discharge (i.e., delithiation and lithiation). Furthermore, valence-to-core (VtC) emission signals helped enable in-depth analysis such as spin structure characterization.
In addition to the XES analysis, we could measure K-edge XAFS for the same 3d transition metals in LiMO2 as well. In the XAFS mode of the spectrometer, SBCA monochromatized bremsstrahlung x-ray generated from a high-power x-ray tube is used to make an incident source energy-dispersive. While Kβ XES probed occupied levels, K-edge XAFS examined unoccupied levels providing comprehensive understanding on the change in electronic structure of 3d transition metals in LiMO2.

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(Invited) Operando ‘Tender’ X-Ray AP-XPS Studies of Ir-Based PEM Electrolyzers
Authors: Hamlyn Rebecca , Crumlin Ethan J. 
Published: November 2022

Synchrotron-based X-ray Photoelectron Spectroscopy (XPS) a is a versatile technique for surface chemical and elemental characterization of materials. Application of this technique to in situ studies was historically challenging in large part due to the attenuation of signal from interaction of photoelectrons with the surrounding environment. With the technological development of ambient pressure systems, we are now able to study catalysts in conditions that resemble their working environments. Further, the use of X-rays in the ‘tender’ regime (2-7 keV) allows for deeper probing than the conventional ‘soft’ x-ray (< 2000 eV) set up that is common at synchrotrons and lab-based sources. The photoelectrons generated from tender x-rays have enough energy to penetrate tens of nanometers through low density components such as a layer of liquid or polymeric electrolyte. This opens the door to access the chemistry at the interface of liquid electrolyte-electrocatalyst materials.
We have built a fully operational two-electrode system for the study of PEM electrolyzers in working conditions. Water flows through the cell and the chamber is held at 100% humidity (20 Torr at 300 K) to yield a fully hydrated environment for our electrocatalyst. We are then able to run operando electrochemical measurements while acquiring XP spectra to elucidate the important physical and chemical processes taking place at the interface. My talk will highlight recent results on iridium-based polymer electrolyte membranes for water splitting. With application of elevated potential, we can correlate the iridium valency and surface species with the appearance of product traces in a mass spectrum.

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X-Ray Crystal Truncation Rod Studies of Electrochemical Double Layers
Authors: Kawaguchi Tomoya , Komanicky Vladimir , Rao Reshma , Shao-Horn Yang , Liu Yihua , You Hoydoo 
Published: November 2022

Electrochemical double layers (EDL) is traditionally described as diffuse distributions of cations and anions, proposed in Gouy and Chapman (GC) model[1] and further developed extensively over decades largely based on voltammetry measurements. However, the GC model is suspected to break down at large potentials, because it predicts the unlimited rise in differential capacitance. Stern suggested long ago that there should be a layer with a finite ion density, known as ‘Stern layer’[2]. While it is generally accepted that Gouy-Chapman model or its modified versions describe well electrochemical interphase structures, recent studies of Pt(111) surface in CsF solution using a model-independent direct inversion method[3] have shown that Stern layer forms over the large double-layer potential range on Pt(111) surface.[4]
In this talk, we present synchrotron x-ray observation of Electrochemical Stern layers on the surfaces of RuO2 single crystals in 0.1 M CsF electrolyte. It is of fundamental importance to study if Stern layer forms on electrode surfaces other than Pt(111). In this case, we will examine RuO2 surfaces and compare the results to that of Pt(111) surface. RuO2 is chosen for several reasons. First, it is a well-studied system because of its oxygen evolution reactions and we are familiar with the structure because of our previous studies.[5,6] Second, it is an oxide with oxygen terminated while Pt is a pure metal. Third, the surfaces of RuO2 are squares or rectangles while that Pt(111) surface is triangles. The Stern layers formed at the interfaces of RuO2 (110) and (100) are compared to the previously reported Stern layer on Pt(111). [4] While the Cs+ density profiles at the potentials close to hydrogen evolution reactions are similar, the hydration layers intervening the surface and the Cs+ layer are significantly denser on RuO2 surfaces than that on Pt(111) surface, reflecting the oxygen termination of RuO2 surfaces. The overall similarities between Stern layers on ruthenium surfaces and platinum surface suggest the universal presence of Stern layers in all well-defined solid-electrolyte interfaces.
[1] Bard, A. J.; Faulkner, L. R., Electrochemical methods: fundamentals and applications. 2nd ed.; John Wiley: New York, 2001.
[2] Stern, O., The theory of the electrolytic double layer. Zeitschrift Für Elektrochemie 1924, 30, 508.
[3] Kawaguchi, T. et al., J. Appl. Cryst., 2018 51, 679.
[4] Liu, Y.; Kawaguchi, T.; Pierce, M.S.; Komanicky, V.; You, H., Layering and Ordering in Electrochemical Double Layers, J Phys Chem Lett, 2018, 9, 1265.
[5] Y.S. Chu, T.E. Lister, W.G. Cullen, H. You, Z. Nagy, Physical Review Letters 2001, 86, 3364.
[6] Rao, R.R. et al., Journal of Physical Chemistry C, 2018, 122, 17802
Mechanistic Insights into Proton Transport in Pure and Aqueous Phosphoric Acid
Authors: Zhu Zhenghao , Popov Ivan , Sokolov Alexei P. , Paddison Stephen J. 
Published: November 2022

The transport of protons plays a key role in a variety of electrochemical processes and technologies. There are two major mechanisms underlying proton transport: the vehicular mechanism where a protonic defect moves with the aid of a molecular entity; and the ‘Grotthuss mechanism’ where a proton diffuses by being transferred between ‘chains’ of host molecules via elementary reactions within the hydrogen bond networks. The latter is regarded as the most efficient proton conductivity mechanism. Although Grotthuss proposed this concept more than 200 years ago, only indirect experimental evidence of the mechanism has thus far been reported. Recently, we observed the first direct experimental observation of proton transfer between the molecules in pure and 85% aqueous phosphoric acid by employing dielectric spectroscopy, and quasi-elastic neutron scattering (QENS). Complementary to these experiments, ab initio molecular dynamics (AIMD) simulations were performed to gain molecular insight into the underlying mechanisms of proton transport allowing for the breaking and forming of covalent bonds since it calculates the forces from electronic structure methods ‘on the fly’.
We calculated the self-intermediate scattering function of the protons, indicating three processes at high Q range consisting of two fast Q-independent processes and one slow Q-dependent process, which are in good agreement with QENS results. Also, the self-part of van Hove function of the protons for the fast characteristic time shows surprisingly short proton jumps of only ~0.5 - 0.7 Å confirmed by analysis of an individual proton trajectory. Furthermore, AIMD demonstrates that proton hopping plays an essential role in the long-range proton diffusion through the breaking and forming of hydrogen bonds. Our analysis confirmed the strong proton-proton correlations in these proton jumps. However, this correlated proton transport unexpectedly leads to a decrease of conductivity in these systems. Based on these results, we propose that the expected Grotthuss-like enhancement mechanism of conductivity cannot be realized in bulk liquids where ionic correlations always reduce conductivity, most likely because of the requirement for the momentum conservation. Our findings will propel the design of electrochemical materials with proton transfers involved in charge transport for achieving high proton conductivity in electrochemical applications including fuel cells.
Modeling and Experimental Analysis of pH Swing-Based Approaches to Electrochemical CO2 Capture
Authors: Kwabi David G. 
Published: November 2022

The use of renewable electricity to drive large-scale electrochemical CO2 removal and concentration from point sources, air, and seawater is receiving considerable interest as one strategy for mitigating climate change.1 The low concentration of CO2 in air however makes rapid and energy-efficient CO2 capture challenging. Understanding and optimizing the energetic cost of CO2 separation at practically reasonable throughputs is a prerequisite for engineering devices that can be widely deployed.
I will review our past and current efforts at developing electrochemical pH-swing-based CO2 separation (EPCS) using a combination of modeling and experiments. In EPCS, CO2 is captured from a mixture of gases into an aqueous electrolyte in the form of (bi)carbonate ions when its pH is increased from acidic to strongly alkaline conditions, and then released as a pure gas when the pH is reversed. We have shown that CO2 separation is experimentally possible for less than 100 kJ/molCO2 using such a pH swing cycle that is driven by proton-coupled electron transfer (PCET).2 Thermodynamic modeling shows that the minimum work input for electrochemical CO2 separation is the sum of exergy losses incurred from differences in CO2 partial pressure between the CO2 source/exit streams and the electrolyte. This framework rationalizes minimum work inputs for pH-swing and redox-mediator-based CO2 separation cycles, and motivates the measurement or estimation of the aforementioned CO2 partial pressures in future experimental studies.
More recently, we have begun to consider a new design for EPCS in which PCET-active species are conformally attached to the internal surface area of a highly porous electrode, and effect a reversible pH swing in an adjacent layer of aqueous electrolyte upon redox cycling. We have formulated a continuum reaction-transport model that simulates reactive CO2 capture into and release from the electrolyte layer, as well as transport of (bi)carbonate species, and protons, in response to an applied current or voltage. Possible pathways toward achieving an energetic cost of direct air capture of CO2 less than 100 kJ/molCO2 will be discussed, as well as our efforts toward experimental demonstration of this concept.

References

Renfrew, S. E.; Starr, D. E.; Strasser, P., Electrochemical Approaches toward CO2 Capture and Concentration. ACS Catalysis
2020,
10 (21), 13058-13074.

Jin, S.; Wu, M.; Gordon, R. G.; Aziz, M. J.; Kwabi, D. G., pH swing cycle for CO2 capture electrochemically driven through proton-coupled electron transfer. Energy & Environmental Science
2020.
Tandem Electrokinetic/Electrocatalytic Remediation of Pfas in Soils
Authors: Lee Katherine , Skinn Brian , Snyder Stephen , Athmer Chris , Inman Maria 
Published: November 2022

Per-/polyfluorinated species (PFAS) are a class of widely used, highly stable chemicals that do not readily break down in the environment or human body. As a result of their widespread use and persistence in the environment, PFAS can be found in soil, air, and water at numerous sites across the United States. Recent work has linked exposure to some types of PFAS found in the environment to adverse health effects in humans. The bio-accumulative nature of PFAS along with the potential adverse health effects has provided strong motivation for active remediation of these emerging contaminants at environmental sites. Development of energy- and cost-efficient technologies for the in-situ treatment of PFAS-contaminated soils would greatly facilitate efforts to remediate these contaminated sites and alleviate the public health threat they represent.
This talk will discuss recent efforts to develop a tandem electrokinetic/electrocatalytic technology for energy-efficient concentration and destruction of PFAS in contaminated soils. In this approach (Figure A), electrokinetic soil remediation technology is used to drive the PFAS contaminants to a localized area around the electrokinetic anode and electrocatalysis reactors situated near this electrokinetic anode degrade and destroy the concentrated PFAS species. Data will be presented describing the electrokinetic transport observed for various C4-C12 linear-chain PFAS in a Dayton, OH till soil on the bench scale (see Figure B). Experimental results to date suggest that larger PFAS species (above ~C6) experience sufficiently strong physicochemical attraction to the soil particles that electrokinetic transport is mostly or completely suppressed. Based on these results, current work is identifying ways to improve electrokinetic PFAS remediation by disrupting these PFAS-soil interactions in a fashion that is economically and environmentally favorable. Results demonstrating the ability to enhance electrocatalytic PFAS destruction through the use of pulsed-waveforms (relative to traditional direct current methods) will also be presented.
Figure Caption. (A) Mechanism of tandem electrokinetic/electrocatalytic PFAS destruction. (B) Bench-scale apparatus for soil electrokinetics tests.

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Using Zirconium MOF Packed Microfluidic Electrochemical Cell As PFOA Screening Sensor in Water Source
Authors: Li Zhenglong , Schmid Julian , Kumar Abhishek , Rahman Maryom , Motkuri Radha Kishan , Basuray Sagnik 
Published: November 2022

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are human-made chemicals with high chemical resistance and thermal stability. The extremely stable fluoro-carbon (F-C) skeletons enable PFAS molecules can exist stably in nature especially in the water sources for a long time concerning thermal, chemical, and biodegradation. Perfluorooctanoic acid (PFOA) is one of the most dominant environmental contributors, and its half-life in water has been estimated to be longer than 92 years. Therefore, the monitoring of PFOA level in the water source is needed. It is reported that Zirconium (Zr) based metal-organic frameworks (MOFs) have shown considerable affinity to PFOA molecules. In addition, electrochemical impedance spectroscopy (EIS) as a rapid and sensitive detection method (based on measuring the impedance changes at the electrode/solution interface) is perhaps the most frequently used technique in the investigation of affinity-based transducers.
In the pursuit of building a highly efficient screening sensor to PFOA molecules. In this work, the application of Zr based MOF in NP-μFEC as a combined sensing platform to PFOA molecules is conducted. Here, the NP-μFEC is our group proposed new impedance sensing platform with enhanced, three-dimensional distributed electric field. To validate the feasibility of Zr based MOF packed NP-μFEC’s sensing performance. The work is conducted with a ranging concentration of PFOA (in 0.1X PBS) from 150 to 10 ng/L. We finally find that the proposed combination of Zr based MOF and NP-μFEC can show an excellent response to the PFOA molecules, which offers a detection limit lower than the established US Environmental Protection Agency (EPA)'s water contamination level (70 ng/L).
What If Electrochemical Energy Systems Were Made 40% More Efficient?
Authors: Leddy Johna 
Published: November 2022

Electrochemical systems related to energy storage and generation have inherent thermodynamic advantages over thermal energy systems because electrochemical systems have do not require moving parts. Thermodynamic Carnot limitations restrict internal combustion engines (ICEs) to about 40% theoretical energy conversion efficiencies. Thermodynamically, electrochemical energy systems can be 100 % efficient. The high thermodynamic efficiency is however challenged by dynamics of kinetics and transport. Because electrochemical energy systems generally operate at lower temperatures and pressures than ICEs, greater finesse in design of catalysis is needed.
Electrochemical energy systems made 40% more efficient would substantially advance the economic and environmental advantages of electrochemical electrochemical energy. Consider mechanisms of physical catalysis where a physical gradient rather than a chemical composition drives chemical change. Magnetoelectrocatalysis is an example of physical catalysis that may provide means to enhance the efficiency of electrochemical energy systems.
Magnetoelectrocatalysis exploits magnetic gradients imposed at electrode surfaces to facilitate electron transfer and so electrocatalysis.
Here, magnetoelectrocatalysis is shown to increase energy, power, and conversion efficiency of several electrochemical energy systems by 40%. Examples include:

Proton exchange membrane (PEM) fuel cells

Alkaline batteries (MnO2|Zn)

Hydrogen evolution reaction (HER) at glassy carbon

MnO2 supercapacitors

Magnetic gradient effects on electrochemical efficiency are also observed for several environmentally relevant electrode reactions.

CO oxidation on Pt

HER on various metal electrodes and photocathodes

C1 reactions at rare earth electrocatalysts

From these outcomes, it is suggested that magnetoelectrochemical catalysis may provide a path to substantially more efficient electrochemical energy systems, perhaps approaching 40%.
Work is undertaken at the University of Iowa. The National Science Foundation (NSF CHE-1309366 and NSF CHE-0809745) and the Army Research Office (W911NF-19-1-0208 (74912-CH-II)) supported these projects.
Dense BaCe0.6Zr0.3Y0.1O3-Α Solid-State Electrolyte for Application in Hydrogen Sensors
Authors: Hinojo Antonio , Lujan Enric Lujan , Colominas Sergi , Abella Jordi 
Published: November 2022

Fusion energy is a promising solution for the expected energy problems in the mid-term future. This technology is expected to use deuterium and tritium, two hydrogen isotopes, as fuel. Deuterium can be obtained from natural sources, but tritium, which is a non-stable hydrogen isotope, must be in situ generated. To assure the correct monitoring of both isotopes, it will be required the design and qualification of high-temperature sensors. The construction of H2 sensors based on solid-state electrolytes can be the first step towards the development of new analytical tools able to monitor hydrogen isotopes in that aggressive environment.
In previous work [1], amperometric sensors based on BaCe0.6Zr0.3Y0.1O3-α (BCZY) solid-state electrolyte have shown good analytical parameters for hydrogen monitoring. However, these materials need high temperatures during sintering to obtain full density due to their refractory nature. This lack of densification can affect their electrochemical response due to their low ionic conductivity. The use of sintering aids, like ZnO, can improve the densification of these ceramics at lower temperatures.
In the present work, hydrogen sensors based on BCZY were constructed and evaluated in potentiometric mode. Different sintering conditions for this electrolyte were tested and their potentiometric response was compared. The following disk-shaped electrolytes were prepared for that purpose: 1400 ºC – 30 h, 1650 ºC – 6h. Simultaneously, BCZY was sintered at 1400 ºC -12 h with 5 mol% of ZnO as a sintering aid. Samples were characterized using XRD (to determine the crystallographic phases) and SEM (for microstructural defects and sintering). Then, disks were platinized and sealed with a glass binder to alumina tubes for sensor construction. Measurements were performed at 400 and 500 ºC. The hydrogen concentration in the RE was 1000 ppm H2 in Ar. The response obtained with the three sensors was compared with the theoretical Nernst potential.
[1] A. Hinojo, I. Soriano, J. Abellà, S. Colominas, Evaluation of High-Temperature Hydrogen Sensors Based on BaCe0.6Zr0.3Y0.1O3-α and Sr(Ce0.9Zr0.1)0.95Yb0.05O3-α Perovskites for Industrial Applications, Sensors. 20 (2020) 7258. https://doi.org/10.3390/s20247258.