Abstract
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 3d5/2 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 3d5/2 photoelectrons.
Highlights
Electricity is one of the most convenient modes of energy that can be very converted into other forms of energy
Supercapacitors are characterized by very high specific power density and capacitance values (up to 175 F g−1 for aqueous and up to 100 F g−1 for nonaqueous electrolyte-based, commercial electrochemical double layer capacitor (EDLC) cells [1,2,3], and from 120 to 150 F g−1 for novel micro-mesoporous carbon electrode-based systems in nonaqueous electrolytes [11,12,13,14,15,16,17,18])
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Summary
Electricity is one of the most convenient modes of energy that can be very converted into other forms of energy. In mobile applications and isolated places, electrical devices should have high specific energy and power density. Two types of reusable powerful electrical energy storage systems are known and applied: rechargeable electrochemical faradic cells and supercapacitors [1,2,3,4,5,6,7,8,9,10,11]. Supercapacitors are characterized by very high specific power density and capacitance values (up to 175 F g−1 for aqueous and up to 100 F g−1 for nonaqueous electrolyte-based, commercial electrochemical double layer capacitor (EDLC) cells [1,2,3], and from 120 to 150 F g−1 for novel micro-mesoporous carbon electrode-based systems in nonaqueous electrolytes [11,12,13,14,15,16,17,18]). The number of recharging cycles that can be applied exceeds
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