Lithium Photo-Intercalation of CdS-Sensitized WO₃ Anode for Energy Storage and Photoelectrochromic Applications.

Integration of solar energy harvesting and storage functions attracts significant research attention as it holds promise for ultimate development of light-chargeable devices. In this context, we investigate a functional nanocomposite anode that does not only permit electrochemical energy storage via Li-ion photo-intercalation, but also exhibits potential for photoelectrochromic applications. The nanocomposite is made of the Li-ion intercalation compound WO3 (thinly coated with TiO2) and sensitized by the photoactive semicoductor CdS. During light exposure, the photoelectrons from CdS are transported to WO3/electrolyte interface where Li-ion intercalation takes place. Photoelectron transport is facilitated by the interfacial TiO2 layer. The WO3 is shown to be functional in multiple cyclic photocharges/discharges, but the CdS to suffer from degradation/photocorrosion. This means that selection of compatible semiconductors and protective coating strategies should be pursued to overcome these issues.