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Several techniques can be applied to characterize redox properties of wide bandgap semiconductors, however some of them are of limited use. In this paper we propose a new modification of the old spectroelectrochemical method developed two decades ago. A procedure based on measurements of the reflectance changes as a function of potential applied to the electrode coated with the studied material appears to be a very convenient tool for characterizing redox properties of semiconductors, forming either transparent or opaque films at a platinum electrode. A discussion on the measured redox parameters of semiconductor films concludes with a definition of a new term, the absorption onset potential of the material.

A group of selected hexafluorometallates ([AlF 6 ] 3− , [TiF 6 ] 2− , [ZrF 6 ] 2− , and [SiF 6 ] 2− ) has been adsorbed at the surface of titanium dioxide. Such modification influenced the electronic and chemical properties of TiO 2 , as well as its photoactivity. The modification with [TiF 6 ] 2− inhibited the efficiency of OH • production but enhanced the generation of photocurrent and singlet oxygen. The results of modifications with [ZrF 6 ] 2− were the oppositegeneration of 1 O 2 was not observed in this case and photocurrents were lower; however, due to a better OH • production, degradation of herbicides was faster.

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