화학공학소재연구정보센터
Journal of Physical Chemistry, Vol.99, No.45, 16676-16683, 1995
Electron-Transport and Frozen Concentration Gradients in a Mixed-Valent Viologen Molten-Salt
This paper shows that electrolytically generated crossed concentration gradients of viologen (2+) and viologen (1+) in films of its mixed valent molten salt on interdigitated array electrodes can be thermally and stably frozen in place in the interelectrode gaps. A study is presented of properties of the gradient-containing films, as compared to films that are non-mixed valent (V2+) Or that are mixed valent but lack concentration gradients. Comparisons of charge transport measurements show that the 2-5 mu m wide concentration gradients are persistent in the molten salt at lowered temperatures, where ionic motions are quenched relative to electron hopping as shown by differences in conductivity between mixed valent and non-mixed valent films as the temperature is lowered from +50 to -70 degrees C. Differences in the magnitude and shape of high-field current-voltage curves taken from mixed valent nongradient and V2+/V+ gradient-containing samples are interpreted with an electron-hopping model that includes a parameter for kinetic dispersity. Differences between the capacitance of the mixed valent and non-mixed valent phase of the viologen molten salt are consistent with the formation of an electronic space charge at the metal/redox conductor interface.