Controllable growth of vertically aligned heterophase TiO₂ nanocones under glycerol assistance toward photocatalytic water purification

TiO₂ nanocone structures (TNCs) have attracted tremendous interest in recent years owing to their intriguing physicochemical properties and potential applications in water purification-related fields. However, the controllable synthesis of high-quality vertically aligned TNCs with a specific phase is crucial for their effective application. Herein, we report the successful synthesis of heterophase TNCs with abundant active edge sites on a titanium foil by designing a glycerol-assisted hydrothermal approach. By tuning the growth parameters of the TNCs, their coverage can be tuned from 62% to 88% and their shapes can be tuned from sparse oblique to vertically aligned. In a photodegradation experiment, the photodegradation rate (K) of vertically aligned TNCs reaches ≈0.01985 min⁻¹, which is five times that of normal TiO₂ dense films (TDFs) under the same conditions, probably owing to their vertical and ordered nanocone array structures, which possess a large specific area, more active edge sites and efficient light harvesting. This work provides an efficient synthetic route for achieving vertically aligned heterophase TNCs, which can serve as perfect platforms for promoting their applications in photocatalytic fields.