Understanding the link between solid/liquid interfaces and photoelectrochemical activity in novel thin-film photoanodes of preferentially oriented high-index rutile TiO2 facets - A work inspired by Michel Che's research on surface chemistry

This work presents the first report of the deposition of a preferentially oriented film of rutile TiO2 exposing high-index facets. Control of the Cl-/F- mol ratio during the hydrolysis of TiCl4 enabled the deposition of different facets of rutile TiO2 on fluorine-doped tin oxide (FTO) substrates. When ranking films of varying facet composition and orientation, the high-index faceted film was found to have a higher activity photoelectrochemical activity towards water oxidation in spite of its low surface energy, as determined by Raman spectroscopy. Complementary photoelectrochemical studies and electron microscopy revealed the higher activity to originate from both the interaction at the electrode/electrolyte interface and the presence of active sites such as coincidence lattice sites in twin boundaries. This work, inspired by the research legacy of Michel Che, highlights the importance of surface chemistry and the presence of active sites in catalytic materials and showcases the coupling of different characterisation techniques to elucidate the mechanism governing the photoelectrochemical behaviour of supported metal oxides. (C) 2020 Elsevier Inc. All rights reserved.