Photoassisted deposition of chalcogenide semiconductors on the titanium dioxide surface: Mechanistic and other aspects

Heterogeneous photocatalysis using photoexcited TiO2 substrates (either in dispersed suspensions or in thin film form) is shown to be a versatile method for preparing Se- or metal selenide (MSe)-modified TiO2 surfaces. The mechanistic aspects underlying this novel preparative route are addressed using chronopotentiometry and linear sweep photovoltammetry. The photovoltammograms of Se/TiO2 composite electrodes exhibit unusual "bipolar" behavior, i.e., both photocathodic and photoanodic enhancement of current flow on the same trace, depending on the imposed potential bias. This interesting photoelectrochemical behavior is rationalized on the basis of the electronic properties of the Se/TiO2 junction. Ex situ characterization of the composite semiconductor samples was also carried out. Finally, an application of CdSe/TiO2 samples for environmental remediation of Cr-VI is demonstrated.