Specific features of the interaction of the surface of mechanically renewable aluminum electrode with molecules of aprotic solvents

The behavior of mechanically renewable aluminum electrode is studied in solutions of tetraethylammonium and lithium salts with surface-inactive anions (ClO4−) in propylene carbonate. The potential region in which Al electrode can be considered as ideally polarizable in these solutions is found. In this potential region, the Al electrode demonstrates a characteristic minimum of the electric double layer capacitance, C, which deepens with electrolyte dilution. Processing experimental С vs. Е dependences within the framework of the classical model of the electric double layer has shown that the position of this capacitance minimum corresponds to the maximum diffusivity of the electric double layer at the zero charge potential. Of special interest is the fact that as we go from tetraethylammonium to lithium solutions, the С vs. Е curves are deformed in the region of negatively charged metal surface and the capacitance minimum disappears. The results obtained on the renewable Al electrode in propylene carbonate solutions are compared with the earlier data obtained on the same electrode in other aprotic solvents (dimethyl formamide, dimethylsulfoxide, and γ-butyrolactone) and an analogy is revealed in the capacitance behavior observed in different solvents upon the transition from solutions containing tetrabutylammonium cations to solutions of lithium salts. The possible reasons for the above effects are put forward and discussed.