Facet-controlled growth and soft-chemical exfoliation of two-dimensional titanium dioxide nanosheets

TiO₂ remains one of the most popular materials used in catalysts, photovoltaics, coatings, and electronics due to its abundance, chemical stability, and excellent catalytic properties. The tailoring of the TiO₂ structure into two-dimensional nanosheets prompted the successful isolation of graphene and MXenes. In this review, facet-controlled TiO₂ and monolayer titanate are outlined, covering their synthesis route and formation mechanism. The reactive facet of TiO₂ is usually controlled by a capping agent. In contrast, the monolayer titanate is achieved by ion-exchange and delamination of layered titanates. Each route leads to 2D structures with unique physical and chemical properties, which expands its utilisation into several niche applications. We elaborate the detailed outlook for the future use and research studies of facet-controlled TiO₂ and monolayer titanates. Advantages and disadvantages of both structures are provided, along with suggested applications for each type of 2D TiO₂ nanosheets.