Titanium dioxide is a well-known catalyst due to its oxidative and hydrolytic properties. Among its other advantages, this material is highly stable and benign toward both humans and the environment. However, its efficiency is strongly dependent on the overall surface area, crystallinity and the synergetic presence of both main phases, namely rutile and anatase. While the last factor is still under study, the tailored formation of crystals with high energy facets has drawn attention in the search for materials with improved water splitting efficiency. Although the synthesis of faceted TiO2 crystals has been widely studied in bulk materials, few reports are found in the literature for the synthesis of TiO2 photoanodes with preferential facet composition for photoelectrochemical water splitting. We therefore synthesized and characterized different rutile TiO2 arrays with a range of different crystal orientations was accomplished by using different titanium precursors as well as different capping agents. Moreover, the interaction of these rutile TiO2 facets with anatase nanoparticles was evaluated by means of their photoelectrochemical activities and the results were described in terms of the surface energies of each rutile TiO2 facet. It was found that the interaction between different phases of titania strongly depends, not only on the degree of crystallinity, but also on the surface energy of either one or both phases. By increasing the crystallinity of the anatase NPs, new heterojunction domains can be created and the electron transfer between the two phases was more favourable for the rutile films with lower surface energy. By creating a heterojunction between the low energy facets of the rutile nanorods (100) and the mesoporous anatase NPs, a 2-fold increase was observed in the photocurrent density compared with the samples made by depositing amorphous TiO2 NPs.

Optimized phase heterojunctions in enhancing the photoelectrochemical activity of TiO2 photoanodes: A surface energy insight

256th National Meeting (2018)

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