Quantification of the synergetic contribution of a buried WO₃/TiO₂ heterojunction to photocatalytic activity

The tungsten trioxide/titanium dioxide (WO₃/TiO₂) heterojunction is archetypical in photocatalysis, with demonstrated synergetic properties despite some controversy around the predominant band model in these systems. The current work is a systematic study that quantifies the synergetic contribution of a WO₃/TiO₂ heterojunction to the enhancement of photocatalytic activity over the contribution of a TiO₂ coating in core–shell nanostructures. The films were produced using atomic layer deposition and chemical vapour deposition techniques and their photocatalytic activity was correlated with transient absorption properties as a function of TiO₂ coating thickness. The study allowed the identification of an optimum thickness range within 21–40 nm, showing the greatest contribution of the heterojunction for a TiO₂ thickness of 30 nm. The outputs of this research have strong implications for heterojunction material design for practical applications.