bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Properties of Bi(111)|1-Ethyl-3-Methylimidazolium Tetracyanoborate and 1-Ethyl-3-Methylimidazolium Iodide Interface
Authors: Siimenson Carolin , Siinor Liis , Lust Enn 
Published: February 2020

Room temperature ionic liquids (RTILs) can sustain substantially higher cell potentials (ΔE) in electrochemical cells without decomposing. For electrochemical double layer capacitors (EDLCs) the widening of the cell potential increases exponentially the energy and power densities. RTILs can be use as electrolytes in modern electrochemical energy devices, such as capacitors, solar cells, batteries and fuel-cells. 1–4

In this work the cyclic voltammetry and electrochemical impedance spectroscopy methods have been applied to investigate the electrical double layer formation and adsorption kinetics parameters of iodide anions at the electrochemically polished Bi(111) electrode surface. The ionic liquid solution was prepared in order to increase the differential capacitance of the system. Therefore 1 wt% 1-ethyl-3-methylimidazolimu iodide (EMImI) was added to 1-ethyl-3-methylimidazolium tetracyanoborate (EMImTCB).
Analysis of current density (j) vs. electrode potential (E) dependencies shows that the Bi(111) electrode is ideally polarizable within the potential range from -1.0 to -0.2 V for 1 wt% vs. Ag| AgCl.
The measured ideal polarizability region is in a good agreement with impedance data. The mixed kinetic processes take place on both systems (Bi(111)|EMImTCB and Bi(111)|EMImTCB + 1%EMImI). Higher capacitance values were obtained for the Bi(111)|EMImTCB + 1%EMImI system. Our recent studies have shown that the addition of specifically adsorbed iodide ions strongly influence the electrochemical characteristics of RTILs systems. 1

Acknowledgments: This study was partially funded by the Estonian Science Foundation Grants 7791, 8357 and 8786, Estonian Energy Technology Program project SLOKT10209T, Estonian Basic Research project SF0180002s08 and Estonian Centers of Excellence in Science project: High-technology Materials for Sustainable Development TK117

References:

1. C. Siimenson, L. Siinor, K. Lust, and E. Lust, J. Electroanal. Chem., 730, 59–64 (2014).
2. T. Tooming et al., J. Electrochem. Soc., 161, A222–A227 (2014).
3. L. Siinor, J. Poom, C. Siimenson, K. Lust, and E. Lust, J. Electroanal. Chem., 719, 133–137 (2014).
4. L. Siinor, K. Lust, and E. Lust, Electrochem. Commun., 12, 1058–1061 (2010).
Electrochemical Activity of Titanium Dioxide Toward Oxygen Reduction and Evolution Reactions
Authors: Tavassol Hadi , Haile Sossina M 
Published: February 2020

We report on the electrochemical activity of TiO2 polymorphs toward oxygen reduction and evolution reactions in a CsH2PO4 solid acid electrochemical system. Oxygen reduction and evolution are catalytically challenging reactions relevant to the fuel cell and water splitting applications. Because of the strong O=O bond, oxygen reduction is a slow reaction even on a Pt surface. In fuel cells, the oxygen reduction reaction (ORR) requires high loadings of the precious Pt catalyst. Even at the operating temperature of the super-protonic CsH2PO4 solid acid, ca. 240 °C, the ORR remains sluggish.
Titanium dioxide has been studied extensively as a promising, low cost (photo)catalyst for water splitting. TiO2 activity toward oxygen led us to examine its catalytic performance for the oxygen reactions in the CsH2PO4 electrochemical system. Solid state TiO2 catalysts on carbon based supports show a range of activity depending on the relative ratio of the rutile to anatase polymorphs. Rutile phase exhibits a lower overpotential for the ORR. The activity of the catalysts are also controlled by the type of the carbon based interconnects used in the fabrication of the composite electrodes. Interconnects facilitate the interaction between CsH2PO4 and TiO2 particles. Catalysis only occurs on TiO2 particles that are connected to the CsH2PO4 electrolyte, and are also accessible to the O2 gas. We will discuss the selective activity of pure and mixed phases of TiO2 rutile and anatase polymorphs toward oxygen reduction and evolution reactions.
Enhancement of Water Oxidation at Tungsten Oxide Photoanodes Doped with Borotungstate-Polyanion Modified-Hematite
Authors: Miecznikowski Krzysztof , Ramirez-Caro Alejandra , Fiechter Sebastian , Kulesza Pawel J 
Published: February 2020

A procedure based on sol-gel aggregation for the fabrication of mesoporous WO3 photoanaodes was adopted to produce the doped oxide films by admixing the tungstic acid sol with Keggin-type borotungstic acid (H5BW12O40) or the borotungstic acid–stabilized hematite (Fe2O3). Such physicochemical properties as structure, morphology and spectroscopic identity of the resulting hybrid (doped) WO3 films were assessed using X-ray diffraction, scanning electron microscopy, as well as UV-Vis and Raman spectrocopies. When using a solar cell system operating in 0.5 mol dm-3 H2SO4 in the three-electrode configuration, the doped WO3 films acting as photoanodes yielded (following illumination with visible light) significantly (up to 80%) larger water oxidation photocurrents (at potentials higher than 0.75 V vs. RHE), in comparison to the analogous undoped mesoporous tungsten oxide films. The effect was the most pronounced in a case of the WO3 film doped with borotungstic acid–stabilized hematite. The observed enhancement effects could be rationalized either in terms of appearance of new conduction band structures in doped WO3 films or a marked increase in the degree of hydration of the doped oxide structures regardless annealing at high temperatures (450 oC). Judging from our experiments in 0.5 mol dm-3 NaCl, the systems are also applicable in the sea-water-type environments. Present results are consistent with the view that the doped tungsten oxide structures do not exhibit significant undesirable electron-hole recombination effects. Optimization of the system is underway aiming at further improvement of the photocurrent efficiency and the systems' utility under different conditions. Any increase in the photoelectrochemical efficiency of WO3–based films is of importance to the development of photoanodes for the visible-light driven water splitting.
Physical-Chemical Properties of the Naf-AlF3-Sc2O3-Al2O3 Molten System
Authors: Tkacheva Olga , Kataev Alexander , Redkin Alexander , Zaikov Yurii 
Published: February 2020

The Al-Sc alloys are typically obtained by aluminothermy method. However, the high alloy’s price is defined by the cost of a scandium-containing substance (such as ScF3 or Sc, etc.) prepared from its raw material (Sc2O3) for the reaction with aluminum. Expenses for a multistage scandium extraction process are also substantial. Another way for producing the Al-Sc alloys can be the electrochemical co-reduction of Al and Sc from their oxides dissolved in a cryolite (NaF-AlF3) melt. To develop the electrolysis process and to determine its operating parameters it is necessary to know some basic physical-chemical properties of the NaF-AlF3-Sc2O3-Al2O3 molten system, such as liquidus temperature, Sc2O3 solubility in cryolite including a cross impact of both Sc2O3 and Al2O3 oxides on their solubility and electrical conductivity of molten mixture. A thermo analysis (TA) was used for liquidus temperature measurements. An oxide solubility was determined by the TA along with isothermic saturation method. An electrical conductivity was measured in the capillary (BN) cell and in the cell with parallel Mo-electrodes using an impedance technique. The obtained results testified that the Sc2O3 behaved similar to the Al2O3. Its additions to the molten cryolite decreased the liquidus temperature and the electrical conductivity. The Sc2O3 solubility in the NaF-AlF3 melt with molar ratio of NaF/AlF3=2.3 was found to be about 10 wt% at 980 ᵒC. The Al2O3 solubility in the scandium-containing cryolite decreased with the Sc2O3 concentration rise. The total solubility of both oxides, in controversial to known data, was determined to be slightly higher than the solubility of each separate oxide in the NaF-AlF3 melt.
NaCl Augmented Phase Transformation in Interfacial Water Under Quasistatic-Loading Conditions
Authors: Khan Shah Haidar , Hoffmann Peter Manfred 
Published: February 2020

From clay swelling to geological transformations, from the structure to functioning of living organism, and from metallic corrosion to the recovery of oil from deeply lying pores, the presence of ions in water at the interface plays an important role. Many studies have been performed to understand the role of ions in water at the interface between solid to solid, solid to liquid and soft matter to liquid media. However, the dynamics and mechanical properties of electrolytic water at the interface have not been completely understood as evident by controversial results and sometime contradictory explanations. Here we present a study of the effects of concentration of NaCl on the stiffness and damping properties of interfacial water confined between mica substrate and an oxidized silicon cantilever. We have used a home-built Scanning Probe Microscope (SPM), based on Fabry-Perot interferometer principle, to monitor the amplitude and phase of the cantilever with <0.1 Å precision. Here we present the behavior of electrolytic water of various NaCl concentrations (0.001-1M) near the interface under different dynamical conditions. We have observed that even under near to ideal static condition (a compression rate of 2 Angstrom per second), the presence of NaCl introduces peaks in the relaxation time not seen in the case of pure water suggesting a phase transformation of the electrolytic water from a liquid-like to more solid-like behavior near the interface. The critical concentration of NaCl suggesting the phase transformation seems to be lying around 0.1 M NaCl. Our detailed and systemic study of the effects of NaCl containing water as compared with pure water under different dynamical conditions may contribute to better understanding of the role of electrolyte in interfacial water as well as help clear some of the underlying controversies in its physics and chemistry.
Investigation of Quantum Confinement in Lead Sulfide Quantum Dots, through Cyclic Voltammetry
Authors: Haram Santosh K , Gujarathi Yogini D 
Published: February 2020

Due to the large Bohr radius (18nm) and formation of the multi-excitons per photon, lead sulfide quantum dots (Q-PbS) have been viewed as an important material in the light harvesting devices. A performance of these devices however is greatly relying on the formation of hetero-junctions for which the knowledge of relative band positions of the components is desirable. These values are normally estimated by ultra-violate photoelectron spectroscopy (UV-PES) and scanning tunneling spectroscopy (STS). In both the cases one need special sample preparation protocols and involved instrumentation. Here, we demonstrated that these parameters can readily be gauged by electrochemical technique such as Cyclic Voltammetry. For that, Q-PbS in the size-range 3-5nm have been prepared by solvo-thermal method and cyclic voltammograms were recorded on their dispersions in dichloromethane. Distinct cathodic and anodic peaks observed in CV have been co-related to the electron transfer, mediated through the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the Q-dots, respectively. Systematic correlation was observed between the size of Q-dots and the position of HOMO and LUMO which is attributed to the quantum confinement of the charge pairs. The results were found to be matched very well with the one reported with PES in air.
Continuum Models for High Molarity Electrolyte Solutions
Authors: Promislow Keith , Gavish Nir 
Published: February 2020

Differential capacitance data is one of the most widely used experimental quantities for characterizing the structure of electrolyte solutions near charged interfaces. Many studies have attempted to fit differential capacitance data to generalized Poisson-Boltzmann models, particularly to account for finite-volume, ion-crowding effects. We consider the inverse problem: the derivation of generalized Poisson-Boltzmann type free energies from prescribed differential capacitance data. The method is applied to differential capacitance data obtained from experiments and from theoretical models typically found in the literature. In particular, we show that differential capacitance data can not uniquely determine finite volume effects, and provide examples for models which give rise to the same differential capacitance data but characterize solutions with very different qualitative features. Further, we show that uniqueness within the class of generalized Poisson-Boltzmann free energies requires knowledge of the excess chemical potential of the system in the bulk (spatially uniform) state. We discuss applications of the derived free energies to models of pore formation within ionomer membranes.
Formic Acid Electrochemical Oxidation on Au25 and Pt@Au24 Nanocatalysts: A DFT Approach
Authors: Clayborne Andre , Chen Wei 
Published: February 2020

Electrooxidation of formic acid has been the focus of intensive investigations due to its importance in the development of low temperature fuel cells. In this work, first principles density functional theoretical calculations were carried out to examine the reaction path for the electrocatalytic oxidation of formic acid on the monolayer-protected Au25 and Pt@Au24 nanoclusters. The Au25-nanocluster oxidizes HCOOH via an indirect pathway; first, forming CO, which can then be reoxidized to form CO2. On the Pt@Au24 nanocluster, it proceeds either through a formate and/or direct path at lower onset potentials than Au25. The calculations present a mechanism for electrochemical experimental observations for formic acid oxidation on monolayer-protected cluster nanocatalysts.
Predicting Transport Properties at Electrode/SEI/Electrolyte Interfaces in Li Ion Batteries
Authors: Qi Yue 
Published: February 2020

The electrode/solid-electrolyte-interphase (SEI)/electrolyte interface is rather complex and critially important in Li-ion battereis. Improving Li transport and preventing electron leakage through the solid electrolyte interphase (SEI) are critical to Li-ion batteries capacity drop and power loss. Identification of the dominant diffusion carriers and their diffusion pathways in main components of SEI is a necessary step to understand the functionality of SEI before tailoring its properties. Therefore, dominant Li diffusion carriers and the ionic conductivity in perfect SEI components (such as Li2CO3 and LiF) were predicted with density functional theory (DFT) over a broad voltage range of the electrode materials that the SEI component covers. It was predicted that the main diffusion carriers in Li2CO3 on anode are excess Li ion interstitials (Li
i

+), however, above 3.98V, Li ion vacancies (V
Li
-) become the dominant. In contrast, the main diffusion carriers in LiF was predicted to be Schottky pairs (V
Li
- and V
F
+), agreeing with experimental observations. While the V
Li
- diffuses through direct hopping, the Li
i

+ diffuses by knocking off the Li+ ion from a lattice. Meso-scale Li+ ion diffusion equations were then formulated based on the diffusion mechanisms discovered by DFT and the boundary conditions of isotope exchange experiments in order to make direct comparison with TOF-SIMS measurements. Furthermore, by studying the point defect formation and diffusion, it is proposed that electron or polaron hopping can be facilitated by the diffusion of point defects, such as Li
i

0 interstitial, when the SEI is thicker than electron tunneling length. Ab initio molecular dynamics of electrode/SEI/electrolyte interface simulations further demonstrated that when a Li
i

0 interstitial transports into the electrolyte, ethylene carbonate (EC) reduction is observed immediately. This is a possible mechanism to explain electron leakage through thick SEI films into the electrolyte.
Multiscale Modeling of a Proton Exchange Membrane Fuel Cell: Atomistic Fuel Cell Model
Authors: Castañeda Ramírez Sergio , Pérez Mendoza Alejandro Esteban , Carmona Juan , Ribadeneira Paz Rafael Esteban 
Published: February 2020

Proton Exchange Membrane Fuel Cells (PEMFCs) are very promising to generate electric energy for transport and electronic devices because they produce minimal pollutant emissions and can operate at low temperature [1]⁠. Despite of enormous progresses made to date, this technology has to reach all technical requirements in order to be competitive.
In this sense, the research of the physicochemical processes in PEMFCs is primordial to characterize and to understand the operation of these devices, aiming to suggest strategies to enhance their performance. Numerical simulations are able to provide detail of quantities that are difficult to measure experimentally, thus they can complement the experimental approaches allowing a comprehensive understanding of the PEMFCs operation [2]⁠.
Several processes on different scales occur in the PEMFC components. The most important processes include the electrochemical reactions in the catalytic layers, ion transport in the electrolyte membrane, and mass transport in all regions of the PEMFC. Different simulation approaches study these processes [3–6]⁠, but these models describe the electrochemical reactions using Butler-Volmer equations with empirical parameters, which rely on operation conditions.
Furthermore, the oxygen reduction reaction (ORR) is fundamental in the development of fuel cells, and it is required a deeper understanding of these macroscopic parameters relating to chemical and structural properties of the catalyst, in order to enhance catalysts and catalytic layers used in this technology. Thus, in this work, it is shown an atomistic approximation using density functional theory (DFT) to describe the reaction processes in the kinetic section of a PEMFC model, which includes transport phenomena at the electrolyte membrane.
It is considered a dissociative mechanism to describe ORR in the cathode of the cell. DFT calculations of a Pt model surface with adsorbed species are carried out to determine activation energies of each elemental step and hence the kinetic parameters are estimated applying the transition state theory.
The kinetic modeling based on DFT calculations enables further insight into reaction mechanisms and deeper understanding of the ORR .
References:
[1] Y. Wang, K.S. Chen, J. Mishler, S.C. Cho, X.C. Adroher, Appl. Energy 88 (2011) 981.
[2] A. A. Shah, K.H. Luo, T.R. Ralph, F.C. Walsh, Electrochim. Acta 56 (2011) 3731.
[3] A.Z. Weber, J. Newman, J. Electrochem. Soc. 151 (2004) A311.
[4] A.Z. Weber, R.L. Borup, R.M. Darling, P.K. Das, T.J. Dursch, W. Gu, D. Harvey, A. Kusoglu, S. Litster, M.M. Mench, R. Mukundan, J.P. Owejan, J.G. Pharoah, M. Secanell, I. V. Zenyuk, J. Electrochem. Soc. 161 (2014) F1254.
[5] P.K. Das, X. Li, Z.-S. Liu, J. Electroanal. Chem. 604 (2007) 72.
[6] W. Sun, B. A. Peppley, K. Karan, Electrochim. Acta 50 (2005) 3359.
Design of Novel Electrochemical Materials from Data-Driven First-Principles Calculations
Authors: Persson Kristin Aslaug 
Published: February 2020

In spirit of Materials Genome Initiative, the Materials Project (http://www.materialsproject.org) aims to leverage the information age for materials design. The goal of the Materials Project is to accelerate materials discovery and education through advanced scientific computing and innovative design methods, scale those computations to inorganic compounds and beyond, and disseminate that information and design tools to the larger materials community. The Project was launched online in October 2011 and since then we have computed and imported > 60,000 inorganic compounds into the database, which can now be freely accessed and searched over through the web interface for many materials properties such as structure, local environments and coordination, XRD, electronic structure, battery electrode properties, elastic tensors, reaction energies and more. In this talk we will highlight some of our results in utilizing the Materials Project infrastructure and wealth of data to understand the limitation of current materials and subsequent design novel materials for electrochemical systems.
Examples will be given on the design of materials for technologies relevant for electrochemical energy storage and harnessing such as Li-ion electrode materials, novel materials for multi-valent intercalation electrodes, electrolytes for multi-valent systems, and transition metal oxide compounds for solar water splitting applications.
Modeling Oxide Formation and Reduction on Platinum
Authors: Eikerling Michael 
Published: February 2020

The formation and reduction of surface oxide species determine both the electrocatalytic activity of Pt towards the oxygen reduction reaction as well as the rate of corrosive Pt dissolution [1]. We perform theory and modeling work to rationalize the various stages of oxide formation and reduction at Pt and, subsequently, use it to explore mechanisms of Pt dissolution. Mechanistic models developed through this work strive to establish relations between metal phase potential and surface oxidation state that govern the transient current response of the electrode. The first part focuses on a recently developed kinetic model for oxide formation and reduction at Pt in the voltage range of 0.65–1.15 V [2]. The model is evaluated against electrochemical [3], spectroscopic [4] and computational studies [5]. The second part presents a kinetic model of oxide growth on platinum in the high voltage regime, above 1.15 V. The governing equations of the oxide growth model account for mass and charge conservation, species migration, and electric field effects. The model is expected to provide insights into different oxide growth mechanisms and to rationalize various growth laws that have been found experimentally. Results will be compared to experimental cyclic voltammetry data to extract rates of kinetic and transport processes. In an ensuing step, platinum dissolution kinetics will be incorporated and linked dynamically to oxide growth and reduction. It is thus expected that the model will be able to explain the dramatically enhanced rate of Pt dissolution that was found in recent experimental studies, when the electrode voltage was cycled through the high voltage regime [6,7,8]. The detailed mechanistic understanding of oxide growth and reduction on platinum will thus complete our theory of platinum dissolution in catalyst layers for polymer electrolyte fuel cells [9].

References

[1] A. Seyeux, V. Maurice, and P. Marcus, J. Electrochem. Soc.
160, C189 (2013).
[2] S. G. Rinaldo, W. Lee, J. Stumper, and M. Eikerling, Electrocatalysis
5, 262 (2014).
[3] A.M. Gómez-Marín, J. Clavilier, J.M. Feliu, J. Electroanal. Chem.
688, 360 (2013)
[4] M. Wakisaka, H. Suzuki, S. Mitsui, H. Uchida, M. Watanabe, Langmuir
25, 1897 (2009)
[5] L. Wang, A. Roudgar, M. Eikerling, J. Phys. Chem.
C
113, 17989 (2009)
[6] S. G. Rinaldo, P. Urchaga, J. Hu, W. Lee, J. Stumper, C. Rice, and M. Eikerling, Phys. Chem. Chem. Phys., in press.
[7] A. A. Topalov, S. Cherevko, A. R. Zeradjanin, J. C. Meier, I. Katsounaros, and K. J. J. Mayrhofer, Chemical Science
5, 631 (2014).
[8] L. Xing, M. A. Hossain, M. Tian, D. Beauchemin, K. T. Adjemian, and G. Jerkiewicz, Electrocatalysis
5, 96 (2014).
[9] S. G. Rinaldo, W. Lee, J. Stumper, and M. Eikerling, Physical Review E
86, 041601 (2012).