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

Integration of solar-energy harvesting and storage functions has attracted significant research attention, as it holds promise for ultimate development of light-chargeable devices. In this context, a functional nanocomposite anode that not only permits electrochemical energy storage through Li-ion photo-intercalation, but also exhibits potential for photoelectrochromic applications, was investigated. The nanocomposite is made of the Li-ion intercalation compound WO₃, thinly coated with TiO₂ and sensitized by the photoactive semiconductor CdS. During light exposure, the photoelectrons from CdS are transported to the WO₃/electrolyte interface, where Li-ion intercalation takes place. Photoelectron transport is facilitated by the interfacial TiO₂ layer. The WO₃ was shown to be functional in multiple photocharge–discharge cycles, but the CdS suffers from degradation and photocorrosion. Hence, the selection of compatible semiconductors and protective coating strategies should be pursued to overcome these issues.