The electrochemical characteristics of the mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium iodide

Another Piece of the Ionic Liquid's Puzzle: Adsorption of Cl- Ions

Classical electrochemical and microscopy methods were used to characterize the interfacial processes of the adsorption of chloride ions from ionic liquids at the Bi(111) single crystal electrode. The mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium chloride was electrochemically characterized by using cyclic voltammetry and electrochemical impedance spectroscopy. In situ scanning tunneling microscopy images showed the formation of superstructures at the electrode's surface over an extended period of time. The specific adsorption of chloride ions reaches an equilibrium state in a more viscous ionic liquid medium slower than in aqueous and organic solvents. Capacitance values increase considerably (also depending on alternative current frequency) at the potential region, where the specific adsorption of chloride ions with partial charge transfer occurs.

The review of advances in interfacial electrochemistry in Estonia: electrochemical double layer and adsorption studies for the development of electrochemical devices

The electrochemistry nowadays has many faces and challenges. Although the focus has shifted from fundamental electrochemistry to applied electrochemistry, one needs to acknowledge that it is impossible to develop and design novel green energy transition devices without a comprehensive understanding of the electrochemical processes at the electrode and electrolyte interface that define the performance mechanisms. The review gives an overview of the systematic research in the field of electrochemistry in Estonia which reflects on the excellent collaboration between fundamental and applied electrochemistry.

Electrochemical Capacitors with Confined Redox Electrolytes and Porous Electrodes

Electrochemical capacitors (ECs), including electrical-double-layer capacitors and pseudocapacitors, feature high power densities but low energy densities. To improve the energy densities of ECs, redox electrolyte-enhanced ECs (R-ECs) or supercapbatteries are designed through employing confined soluble redox electrolytes and porous electrodes. In R-ECs the energy storage is based on diffusion-controlled faradaic processes of confined redox electrolytes at the surface of a porous electrode, which thus take the merits of high power densities of ECs and high energy densities of batteries. In the past few years, there has been great progress in the development of this energy storage technology, particularly in the design and synthesis of novel redox electrolytes and porous electrodes, as well as the configurations of new devices. Herein, a full-screen picture of the fundamentals and the state-of-art progress of R-ECs are given together with a discussion and outlines about the challenges and future perspectives of R-ECs. The strategies to improve the performance of R-ECs are highlighted from the aspects of their capacitances and capacitance retention, power densities, and energy densities. The insight into the philosophies behind these strategies will be favorable to promote the R-EC technology toward practical applications of supercapacitors in different fields.

in Situ X-ray Photoelectron Spectroscopic and Electrochemical Studies of the Bromide Anions Dissolved in 1-Ethyl-3-Methyl Imidazolium Tetrafluoroborate

Influence of electrode potential on the electrochemical behavior of a 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF₄) solution containing 5 wt % 1-ethyl-3-methylimidazolium bromide (EMImBr) has been investigated using electrochemical and synchrotron-initiated high-resolution in situ X-ray photoelectron spectroscopy (XPS) methods. Observation of the Br 3d_5/2 in situ XPS signal, collected in a 5 wt % EMImBr solution at an EMImBF₄–vacuum interface, enabled the detection of the start of the electrooxidation process of the Br⁻ anion to Br₃⁻ anion and thereafter to the Br₂ at the micro-mesoporous carbon electrode, polarized continuously at the high fixed positive potentials. A new photoelectron peak, corresponding to B–O bond formation in the B 1s in situ XPS spectra at E ≤ −1.17 V, parallel to the start of the electroreduction of the residual water at the micro-mesoporous carbon electrode, was observed and is discussed. The electroreduction of the residual water caused a reduction in the absolute value of binding energy vs. potential plot slope twice to ca. dBE dE⁻¹ = −0.5 eV V⁻¹ at E ≤ −1.17 V for C 1s, N 1s, B 1s, F 1s, and Br 3d_5/2 photoelectrons.