ELECTROGENERATED ION TRANSFER ACROSS TOLUENE+IONIC LIQUID MIXTURE / AQUEOUS SOLUTION INTERFACE

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MEASUREMENT OF INTERFACIAL TENSION BY LOCATING AN AIR BUBBLE ON THE OIL|WATER INTERFACE

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SECM study of hydrogen photogeneration in a 1,2-dichloroethane | water biphasic system with decamethylruthenocene electron donor regeneration

This paper reports light driven hydrogen evolution reaction (HER) at 1,2-dichloroethane | water (DCE | W) interface using photoexcited decamethylruthenocene (DMRc) as electron donor. DMRc is in situ regenerated by electroreduction of its oxidized form (DMRc+) formed during HER as a by-product. This enables continuous HER using small amount of DMRc. Proton transfer from the acidic aqueous phase to the DCE phase is ensured by negative chemical polarization of the liquid | liquid interface. The reduction of protons in DCE occurs only after excitation of DMRc by light. Voltammetry performed with the organic droplet-modified glassy carbon electrode immersed in the aqueous electrolyte solution of various anions, indicated that oxidation of DMRc is followed by an anion insertion from water into the organic phase. We demonstrate that DMRc can be electrochemically regenerated at the microelectrode positioned close to the interface between two immiscible electrolyte solutions (ITIES) by the scanning electrochemical microscopy. Regeneration of the electron donor allows further development of biphasic system towards continuous hydrogen generation platform

Scanning electrochemical microscopy determination of hydrogen flux at liquid|liquid interface with potentiometric probe

Scanning electrochemical microscopy potentiometric determination of local hydrogen concentration and its flux next to the liquid|liquid interface was demonstrated. This method is based on the shift of open circuit potential of Pt-based reversible hydrogen electrode. The detection system was verified with a system generating hydrogen under galvanostatic conditions. Then, it was applied to aqueous|1,2-dichloroethane interface where hydrogen is produced with decamethylferrocene as electron donor

H2O2 generation at carbon paste electrode with decamethylferrocene solution in 2-nitrophenyloctyl ether as a binder. The catalytic effect of MoS2 particles

Here, we report hydrogen peroxide generation at 2-nitrophenyloctyl ether (NPOE)-water interface with decamethylferrocene as an electron donor. The progress of this reaction was detected by the observation of color change of the organic and aqueous phases in series of shake-flask experiments. The shape change of cyclic voltammograms recorded at carbon paste electrode with decamethylferrocene solution in NPOE also indicates (electro)catalytic reaction. Hydrogen peroxide was electrochemically detected at Pt microelectrode tip positioned in front of carbon paste electrode. For this purpose, scanning electrochemical microscopy (SECM) approach curves were recorded. Analogous experiments demonstrated the possibility of electrochemical regeneration of the electron donor. The (electro)catalytic effect of MoS2 on hydrogen peroxide generation was found by both shake-flask and SECM experiments

Mechanism of oxygen reduction by metallocenes near liquid|liquid interfaces

The mechanism of the oxygen reduction reaction (ORR) at a liquid|liquid interface, employing ferrocene (Fc) derivatives – such as decamethylferrocene (DMFc) – as a lipophilic electron donor along with sulfuric acid as an aqueous proton source, was elucidated through comparison of experimentally obtained cyclic voltammograms (CVs) to simulated CVs generated through COMSOL Multiphysics software which employs the finite element method (FEM). The simulations incorporated a potential dependent proton transfer (i.e . ion transfer, IT) step from the water (w) to organic (o) phases along with two homogeneous reactions (C1C2) occurring in the organic phase – an IT-C1C2 mechanism. The reaction of DMFc with H+(o) to form DMFc-hydride (DMFc-H+) was considered the first step (reaction 1), while reaction of DMFc-H+ with oxygen to form a peroxyl radical species, View the MathML sourceHO2, and DMFc+ was deemed the second step (reaction 2). Subsequent reactions, between View the MathML sourceHO2 and either DMFc or H+, were considered to be fast and irreversible so that 2 was a ‘proton-sink’, such that further reactions were not included; in this way, the simulation was greatly simplified. The rate of 1, kcf, and 2, kchem, were determined to be 5 × 102 and 1 × 104 L mol−1 s−1, respectively, for DMFc as the electron donor. Similarly, the rates of biphasic ORR for 1,1′-dimethylferrocene (DFc) and Fc were considered equivalent in terms of this reaction mechanism; therefore, their rates were determined to be 1 × 102 and 5 × 102 L mol−1 s−1 for 1 and 2, respectively. The reactive and diffusive layer thicknesses are also discussed

Molecular Precursor Routes for Ag-Based Metallic, Intermetallic, and Metal Sulfide Nanoparticles: Their Comparative ORR Activity Trend at Solid|Liquid and Liquid|Liquid Interfaces

The electrochemical conversion of oxygen to water is a crucial process required for renewable energy production, whereas its first two-electron step produces a versatile chemical and oxidant─hydrogen peroxide. Improving performance and widening the limited selection of the potential catalysts for this reaction is a step toward the implementation of clean-energy technologies. As silver is known as one of the most effective catalysts of oxygen reduction reaction (ORR), we have designed a suitable molecular precursor pathway for the selective synthesis of metallic (Ag), intermetallic (Ag3Sb), and binary or ternary metal sulfide (Ag2S and AgSbS2) nanomaterials by judicious control of reaction conditions. The decomposition of xanthate precursors under different reaction conditions in colloidal synthesis indicates that carbon–sulfur bond cleavage yields the respective metal sulfide nanomaterials. This is not the case in the presence of trioctylphosphine when the metal–sulfur bond is broken. The synthesized nanomaterials were applied as catalysts of oxygen reduction at the liquid–liquid and solid–liquid interfaces. Ag exhibits the best performance for electrochemical oxygen reduction, whereas the electrocatalytic performance of Ag and Ag3Sb is comparable for peroxide reduction in an alkaline medium. Scanning electrochemical microscopy (SECM) analysis indicates that a flexible 2-electron to 4-electron ORR pathway has been achieved by transforming metallic Ag into intermetallic Ag3Sb