Semiconductors As Selective Redox Electrodes.

摘要

Electrodes that selectively exchange charge with only certain redox couples in a mixture could improve the performance of photogalvanic and bio-photovoltaic cells described in the literature. One avenue to achieve selectivity is through the use of semiconducting rather than metallic electrodes to exploit the presence of the bandgap to control reaction rates. In this paper, Fluorine doped Tin oxide (F:SnO_2), Copper(ll) oxide (CuO) and Nickel oxide (NiO) electrodes are investigated as a means to achieving selective redox reactions. The reactions of methyl viologen, ferricyanide/ferrocyanide and ferric/ferrous couples on the three semiconducting electrodes were studied using cyclic voltammetry and sampled current voltammetry. The rate of electron transfer between the electrodes and the redox couples depended on the difference between the semiconductor majority carrier band edge and the standard redox potential of the redox couple. Most noticeably, the rate constant of methyl viologen on F:SnO_2 was two orders of magnitude higher than that for the ferric/ferrous ion. Similar results were obtained with the NiO electrode while electrochemical instability hampered the tests of the CuO electrode.