|Budget Amount *help
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2000: ¥2,500,000 (Direct Cost: ¥2,500,000)
The "macro-interface" in the title means common electrode | solution or oil | water interfaces, whereas the "nano-interface" means molecular-level interfaces between an ion and solvent molecules. Recently, we proposed a new, non-Bornian theory of the Gibbs transfer energy of ions across the oil | water interface, in which the ion-solvent interaction energy was given by a quadratic function of the surface field strength of an ion. This dependence is very similar to the potential dependence of surface tension of a mercury electrode (I.e. , electrocapillary curves). We then established a working hypothesis―If interfacial energies of macro- and nano-interfaces are intrinsically the same, the surface energy of a mercury electrode as a macro-interface will also be expressed by a quadratic function of the surface field (E) of the electrode, and the second-order coefficient will correlate with empirical solvent parameters such as donor number (D_N), acceptor number (A_N) , etc.
In order to verify this working hypothesis, the differential capacities of a mercury electrode in various solvents were measured by means of an a.c. impedance method. By using the capacity data, the interfacial energy (γ_1) of the electrode, being corrected for the contribution from the diffuse double layer, was determined as a function of E. For every solvent, γ_1 could be given by a quadratic function of E in either positive or negative potential range. The second-order coefficients, a_+ and a_-, were then evaluated for E > 0 and E < 0. Regarding all ten solvents examined, the values of a_+ and a_- did not show good correlation with any properties of the solvents. However, when excluding two solvents, formamide and N-methylformamide, the a_+ and a_- values showed good correlation with empirical solvent parameters such as D_N (r = 0.821) and A_N (r = 0.910), thus supporting the working hypothesis.