Use of CO as a cleaning tool of highly active surfaces in contact with ionic liquids. Ni deposition on Pt(111) surfaces in IL

This work proposes a pretreatment strategy of a flame-annealed Pt(111) single crystal ensuring surface ordering and avoiding surface contamination for experiments in ionic liquid (IL) media,. A room temperature ionic liquid (RTIL) and a Deep Eutectic Solvent (DES) representative of two families of ionic liquids were selected as test electrolytes: The RTIL used was the 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethyl)sulfonylimide ([Emmim][Tf2N]) and the DES was based on the eutectic mixture of choline chloride (ChCl) and urea (1ChCl:2urea molar ratio). The electrode was flame-annealed and cooled down in CO atmosphere until the surface was fully covered by a protective carbon monoxide (CO) layer. Prior to experiments, the removal of CO from the surface was performed by electrochemical oxidation. The CO reactivity on Pt(111) was different depending on the IL nature. While CO is oxidised easily to CO2 in [Emmim][Tf2N], in DES CO remains adsorbed on the substrate and restructures undergoing an order-disorder transition. For both liquids, the proposed method allows obtaining neat blank cyclic voltammograms, demonstrating that the adsorption of CO is a useful tool to protect the high catalytic surfaces such as Pt in contact with ILs. To illustrate the feasibility of the CO treatment in electrochemical work with ILs, the general trends for the modification of Pt(111) single crystal surface with metallic nickel nanostructures on both types of IL was investigated. Nickel electrodeposition on Pt(111) surface was explored in both [Emmim][Tf2N] and DES by using classical electrochemical techniques such as cyclic voltammetry and chronoamperometry, and the deposits were characterized by FE-SEM ,EDS and XPS

Use of CO as a Cleaning Tool of Highly Active Surfaces in Contact with Ionic Liquids: Ni Deposition on Pt(111) Surfaces in IL

This work proposes a pretreatment strategy of a flame-annealed Pt(111) single crystal ensuring surface ordering and avoiding water surface contamination for experiments in ionic liquid (IL) media. A room temperature ionic liquid (RTIL) and a deep eutectic solvent (DES) representative of two families of ionic liquids were selected as test electrolytes: The RTIL used was the 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethyl)sulfonylimide ([Emmim][Tf2N]), and the DES was based on the eutectic mixture of choline chloride (ChCl) and urea (1ChCl:2urea molar ratio). The electrode was flame-annealed and, instead of the water quenching step, it was cooled down in CO atmosphere until the surface was fully covered by a protective carbon monoxide (CO) layer. Prior to experiments, the removal of CO from the surface was performed by electrochemical oxidation. The CO reactivity on Pt(111) was different depending on the IL nature. While CO is easily oxidized to CO2 in [Emmim][Tf2N], in DES, CO remains adsorbed on the substrate and restructures undergoing an order–disorder transition. For both liquids, the proposed method allows for obtaining neat blank cyclic voltammograms, demonstrating that the adsorption of CO is a useful tool to protect the high catalytic surfaces, such as Pt in contact with ILs. To illustrate the feasibility of the CO treatment in electrochemical work with ILs, the general trends for the modification of Pt(111) single crystal surface with metallic nickel nanostructures on both types of IL was investigated. Nickel electrodeposition on the Pt(111) substrate was explored in both [Emmim][Tf2N] and DES by using classical electrochemical techniques, such as cyclic voltammetry and chronoamperometry, while the deposits were characterized by FE-SEM, EDS, and XPS.This work has been financially supported by the MCINN-FEDER (Spain) through the projects: CTQ2016-76221-P and TEC2017-85059-C3-2R. P. Sebastian acknowledges MECD for the award of a FPU grant

The influence of structural features on vibration of the propeller engine test bench

The paper concerns the prototype of a propeller engine test bench stand designed for durability tests of airplane piston engines of 150-250 kW power range (Ostapski, 2011b, 2008). The technical data of the prototype engines to be tested on the bench have been adopted. It is obvious that at the beginning of the design process there is no information about the vibration spectrum of the propeller shaft, which is at the production process at that time. The basic 3D model of test bench constructional variants are presented in the article. Modes and frequencies of free vibrations are defined in ANSYS environment for both the loaded and unloaded structure and for various design variants. The estimated vibration frequency range for the propeller shaft varies from ƒ = 22 to ƒ = 360 Hz. In such a case, there is no easy way for rational test bench construction to be completely “untuned” to the vibration forcing load. This is the reason for introducing the basic model and few its modifications. After first engine tests, it should be possible to separate natural vibrations of the bench and high amplitude vibrations of the engine

The influence of structural features on vibration of the propeller engine test bench

The paper concerns the prototype of a propeller engine test bench stand designed for durability tests of airplane piston engines of 150-250 kW power range (Ostapski, 2011b, 2008). The technical data of the prototype engines to be tested on the bench have been adopted. It is obvious that at the beginning of the design process there is no information about the vibration spectrum of the propeller shaft, which is at the production process at that time. The basic 3D model of test bench constructional variants are presented in the article. Modes and frequencies of free vibrations are defined in ANSYS environment for both the loaded and unloaded structure and for various design variants. The estimated vibration frequency range for the propeller shaft varies from ƒ = 22 to ƒ = 360 Hz. In such a case, there is no easy way for rational test bench construction to be completely “untuned” to the vibration forcing load. This is the reason for introducing the basic model and few its modifications. After first engine tests, it should be possible to separate natural vibrations of the bench and high amplitude vibrations of the engine

Catalytic reduction of TFSI-containing ionic liquid in the presence of lithium cations

The influence of the electrochemical double layer (EDL) structure on the electrochemical processes in ionic liquids is an intriguing subject. The complex layered structure of the EDL and its restructuring have been shown to strongly affect metal deposit morphology and electrochemical reaction kinetics. In this work, we demonstrate that the breakdown of an ionic liquid containing TFSI anions can be catalyzed through the addition of Li+ cations. We ascribe this catalytic effect to the change in the EDL structure: the Li+ cations preferentially adsorb on the electrode surface and drag the TFSI anions with them, facilitating their reduction. The decomposition of the ionic liquid leads to the formation of an SEI layer, which is studied using an electrochemical quartz crystal microbalance. Keywords: Double layer, Ionic liquids, SEI, EQCM, Lithium, XP

Solvent-Dependent Oxidizing Power of LiI Redox Couples for Li-O2 Batteries

Li-O₂ batteries offer higher gravimetric energy density than commercial Li-ion batteries. Despite this promise, catalyzing oxidation of discharge products, Li₂O₂ and LiOH, during charging remains an obstacle to improved cycle life and round-trip efficiency. In this work, reactions between LiI, a soluble redox mediator added to catalyze the charging process, and Li₂O₂ and LiOH are systematically investigated. We show that stronger solvation of Li⁺ and I⁻ ions led to an increase in the oxidizing power of I₃⁻, which allowed I₃⁻ to oxidize Li₂O₂ and LiOH in DMA, DMSO, and Me-Im, whereas in weaker solvents (G4, DME), the more oxidizing I₂ was needed before a reaction could occur. We observed that Li₂O₂ was oxidized to O₂, whereas LiOH reacts to form IO⁻, which could either disproportionate to LiIO₃ or attack solvent molecules. This work clarifies significant misconceptions in these reactions and provides a thermodynamic and selectivity framework for understanding the role of LiI in Li-O₂ batteries

Use of CO as a cleaning tool of highly active surfaces in contact with ionic liquids. Ni deposition on Pt(111) surfaces in IL

This work proposes a pretreatment strategy of a flame-annealed Pt(111) single crystal ensuring surface ordering and avoiding surface contamination for experiments in ionic liquid (IL) media,. A room temperature ionic liquid (RTIL) and a Deep Eutectic Solvent (DES) representative of two families of ionic liquids were selected as test electrolytes: The RTIL used was the 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethyl)sulfonylimide ([Emmim][Tf2N]) and the DES was based on the eutectic mixture of choline chloride (ChCl) and urea (1ChCl:2urea molar ratio). The electrode was flame-annealed and cooled down in CO atmosphere until the surface was fully covered by a protective carbon monoxide (CO) layer. Prior to experiments, the removal of CO from the surface was performed by electrochemical oxidation. The CO reactivity on Pt(111) was different depending on the IL nature. While CO is oxidised easily to CO2 in [Emmim][Tf2N], in DES CO remains adsorbed on the substrate and restructures undergoing an order-disorder transition. For both liquids, the proposed method allows obtaining neat blank cyclic voltammograms, demonstrating that the adsorption of CO is a useful tool to protect the high catalytic surfaces such as Pt in contact with ILs. To illustrate the feasibility of the CO treatment in electrochemical work with ILs, the general trends for the modification of Pt(111) single crystal surface with metallic nickel nanostructures on both types of IL was investigated. Nickel electrodeposition on Pt(111) surface was explored in both [Emmim][Tf2N] and DES by using classical electrochemical techniques such as cyclic voltammetry and chronoamperometry, and the deposits were characterized by FE-SEM ,EDS and XPS

Tandem Interface and Bulk Li-Ion Transport in a Hybrid Solid Electrolyte with Microsized Active Filler

In common hybrid solid electrolytes (HSEs), either the ionic conductivity of the polymer electrolyte is enhanced by the presence of a nanosized inorganic filler, which effectively decrease the glass-transition temperature, or the polymer solid electrolyte acts mostly as a flexible host for the inorganic solid electrolyte, the latter providing the conductivity. Here a true HSE is developed that makes optimal use of the high conductivity of the inorganic solid electrolyte and the flexibility of the polymer matrix. It is demonstrated that the LAGP (Li1.5Al0.5Ge1.5(PO4)3) participates in the overall conductivity and that the interface environment between the poly(ethylene oxide) (PEO) and LAGP plays a key role in utilizing the high conductivity of the LAGP. This HSE demonstrates promising cycling versus Li-metal anodes and in a full Li-metal solid-state battery. This strategy offers a promising route for the development of Li-metal solid-state batteries, aiming for safe and reversible high-energy-density batteries.RST/Storage of Electrochemical Energ

Controlling Solution-Mediated Reaction Mechanisms of Oxygen Reduction Using Potential and Solvent for Aprotic Lithium–Oxygen Batteries

Fundamental understanding of growth mechanisms of Li₂O₂ in Li–O₂ cells is critical for implementing batteries with high gravimetric energies. Li₂O₂ growth can occur first by 1e^– transfer to O₂, forming Li⁺–O₂^– and then either chemical disproportionation of Li⁺–O₂^–, or a second electron transfer to Li⁺–O₂^–. We demonstrate that Li₂O₂ growth is governed primarily by disproportionation of Li⁺–O₂^– at low overpotential, and surface-mediated electron transfer at high overpotential. We obtain evidence supporting this trend using the rotating ring disk electrode (RRDE) technique, which shows that the fraction of oxygen reduction reaction charge attributable to soluble Li⁺–O₂^–-based intermediates increases as the discharge overpotential reduces. Electrochemical quartz crystal microbalance (EQCM) measurements of oxygen reduction support this picture, and show that the dependence of the reaction mechanism on the applied potential explains the difference in Li₂O₂ morphologies observed at different discharge overpotentials: formation of large (∼250 nm–1 μm) toroids, and conformal coatings (<50 nm) at higher overpotentials. These results highlight that RRDE and EQCM can be used as complementary tools to gain new insights into the role of soluble and solid reaction intermediates in the growth of reaction products in metal–O₂ batteries