Electrochemical neutral aqueous electrolytes

Many studies of electrochemical reduction of CO2 in early years were carried out in aqueous media with metal electrodes of high hydrogen overvoltage such as mercury and lead, aiming at suppression of HER. Eyring and his coworkers studied CO2 reduction at a Hg electrode in detail they showed that HCOO is exclusively produced with the faradaic efficiency 100% in neutral aqueous electrolytes. Hori and Suzuki revealed that the partial current of HCOO formation at a Hg electrode does not depend on pH at a constant potential, whereas HER is proportional to proton activity. " ... 

Qu, Q., P. Zhang, B. Wang et al. 2009. Electrochemical performance of MnOj nanorods in neutral aqueous electrolytes as a cathode for asymmetric supercapacitors. Journal of Physical Chemistry C 113 14020-14027. 

Xia, H., Y. Shirley Meng, G. Yuan, C. Cni, and L. Lu. 2012. A symmetric RnOj/ Rn02 snpercapacitor operating at 1.6 V by nsing a neutral aqueous electrolyte. Electrochemical and Solid-State Letters 15 A60-A63. 

Xia, H., and C. Huo. 2011. Electrochemical properties of MnOj/CNT nanocomposite in neutral aqueous electrolyte as cathode material for asymmetric supercapacitors. International Journal of Smart and Nano Materials 2 283-291. 

EFCs are electrochemical systems that consist of an anode, a cathode, and an electrolyte. Design of EFC prototypes was inspired by conventional batteries and fuel cells, but there are substantial differences that lead to completely new design concepts and requirements. Specifically, in contrast to conventional batteries, the oxidized substance in the EFC is not carried in the electrodes, but instead stored as a fuel. In contrast to conventional fuel cells, EFCs use highly selective enzymes in the anode and cathode reactions and they can operate without any membrane separation, in neutral aqueous electrolyte, and at room temperature and are capable to provide deep, or complete, fuel oxidation. 

First electrochemical studies on structuring and modification of different high superconductor surfaces have recently been started [6.190]. One of the main problems is the instability of oxide ceramic material in neutral and acidic aqueous electrolyte solutions at room temperature [6.196-6.198]. HTSC surfaces corrode, and superconductivity was found to decrease within the topmost layers of IfTSC samples after water contact. This aging effect decreases in alkaline media [6.197]. However, sufficient long term stability of HTSC samples was only found in aprotic solvents such as acetonitrile. Therefore, experiments were carried out in acetonitrile-containing... 

These surface groups are considered less stable and include such groups as carboxyl, lactonic, and phenol ones. Basic and neutral surface oxides are considered to be more stable than acidic oxides and tend to contact oxygen at low temperatures. Functional groups that are electrochemically inert in the range of working potentials can cause an increase in the wettability of carbon electrodes and therefore enhance specific capacitance of carbon by improving access of aqueous electrolytes to pores that results in better use of the surface. 

Neutral electrolytes have been scarcely applied for carbon-based supercapacitors. Indeed, the capacitance values of activated carbons in neutral electrolytes are lower than in other aqueous electrolytes, suggesting that the pseudo-faradic redox reactions of O and N electroactive surface groups are depressed in comparison with acidic or basic electrolytes [25, 27, 57-59]. Therefore, it was concluded that oxygenated or nitrogenated functionalities are electrochemically inactive in neutral electrolytes and that only the formation of the electrical double layer contributes to the capacitance in this media. 

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