Electron Transfer Reactions at Liquid-Liquid Interfaces

Abstract

Liquid-liquid interfaces can be polarised to carry out charge transfer reactions, in particular electron transfer (ET) reactions between a hydrophilic and a lipophilic redox molecule. These reactions can be studied by classical electrochemical methods such as cyclic voltammetry. By combining spectroscopic time resolved techniques such Surface Second Harmonic Generation with electrochemical methods, we have studied photo-initiated electron transfer reactions between adsorbed porphyrins and redox quenchers located in one of the adjacent phases. By this approach, we can measure the ET kinetics of adsorbed species located mainly at the interface. We have shown that these interfacial ET reactions involving surface species are not sensitive to the interfacial polarisation. More generally, ET reactions at polarised liquid-liquid interfaces will be discussed to place the present results in perspective. In the second part of the talk, the concept of photo-ionic cells will be presented. Here, the photo-products of a photo-ET reactions occurring in the interfacial region are separated between the two adjacent immiscible phases, thereby resulting in energy storage. This electrochemical energy can then be recovered in a classical parallel plate flow cell. We shall discuss the pros and cons of this method of production of solar fuels.