Electrochemical reversibility of Me6Fc/Me6Fc+PF6- and Me8Fc/Me8Fc+PF6- redox systems in acetonitrile

Two new redox systems, sym. 1,2,4,1¢,2¢,4¢-hexamethylferrocene/cation sym. 1,2,4,1¢,2¢,4¢-hexamethyl ferricinium and sym. octamethylferrocene/cation sym. Octamethyl­ferricinium (MenFc/MenFc+, n = 6, 8) were studied by the cyclic voltammetry method. The observed dif­ference between potentials of anodic and cathodic peaks of 0.063 to 0.075 V, and its inde­pendence on the potential scan rate, the straight-line depen­dence of the current value of anodic (and cathodic) peak on square root of the potential scan rate, as well as shapes of the recorded cyclic voltammograms indicate that both redox systems in acetonitrile meet the most important requirement of IUPAC regarding internal reference redox systems (IRRS) - electrochemical reversibility of electron transfer reaction. The same method under identical conditions was used to study the effect of the number of methyl groups on the redox potential of MenFc/MenFc+ systems, n = 0, 6, 8, 10. It was shown that the successive displacement of half-wave potential in the series of Fc/Fc+ - Me6Fc/Me6Fc+ - Me8Fc/Me8Fc+ -Me10Fc/Me10Fc+ towards negative potentials is attributed to the electron-donor property of methyl groups. The location of the redox potentials values of new systems [n=6 (111 mV), n=8 (23 mV)] between redox potentials of systems of n = 0 (431 mV) and n = 10 (-77 mV) means that the redox potential of the systems of MenFc/MenFc+(n = 6, 8) has an optimal position on the electrode potential scale, i.e. meets another of the IUPAC criteria for IRRS.

Recent advances in cathode engineering to enable reversible room-temperature aluminium–sulfur batteries

The electrochemical reversibility of the aluminum–sulfur (Al–S) battery critically depends on the physical and chemical properties of the sulfur cathode.

Solvent-Dictated Sodium Sulfur Redox Reactions: Investigation of Carbonate and Ether Electrolytes

Sulfur-based cathode chemistries are essential for the development of high energy density alkali-ion batteries. Here, we elucidate the redox kinetics of sulfur confined on carbon nanotubes, comparing its performance in ether-based and carbonate-based electrolytes at room temperature. The solvent is found to play a key role for the electrochemical reactivity of the sulfur cathode in sodium–sulfur (Na–S) batteries. Ether-based electrolytes contribute to a more complete reduction of sulfur and enable a higher electrochemical reversibility. On the other hand, an irreversible solution-phase reaction is observed in carbonate solvents. This study clearly reveals the solvent-dependent Na–S reaction pathways in room temperature Na–S batteries and provides an insight into realizing their high energy potential, via electrolyte formulation design.

Dipyridinoarsole: a new class of stable and modifiable heteroatom-bridged bipyridines

Dipyridinoarsole, having high air-stability and electrochemical reversibility, has been experimentally and computationally studied. The chemical structure was selectively modified to tune the absorption and emission wavelengths and to realize electrochromism.