Exfoliation of titanium oxide powder into nanosheets using hydrothermal reaction and its reassembly into flexible papers for thin-film capacitors

•TiOx single sheets, a novel 2-dimensional material, were exfoliated from bulk powders via the modified Sasaki’s method.•In our method, the acid treatment of TiOx bulk powders was simply modified by applying the hydrothermal reaction.•Then, the delamination procedures of large cation exchange were conducted following the method proposed by Sasaki et al.•Reassembly of TiOx sheets into flexible free-standing films was simply achieved via vacuum assisted filtration method.•TiOx films were used as a flexible supercapaictor electrode material.

We have discovered a methodology to realize the fabrication of flexible metal oxide film using two-dimensional (2D) nanosheets. Atomic scale titanium oxide (TiOx) nanosheets were exfoliated from bulk TiOx powder that had a layered structure via the modified Sasaki’s method. The vacuum-assisted filtration generates films with laterally aligned TiOx nanosheets. The 2D sheet-like structure and hydrophilic nature of TiOx nanosheets enables the film consisting of TiOx nanosheets to be bendable. Also, we demonstrate the fabrication of electrochemical capacitors using this film. The mechanically flexible metal oxide film is expected to open up the possibility of fabricating flexible energy storage devices from 2D metal oxide nanosheets.

Graphical abstractThe modified Sasaki’s method, combined process of hydrothermal reaction and bulky ion exchange, enables to obtain TiOx monolayer nanosheets. The vacuum-assisted filtration generates bendable films with laterally aligned TiOx nanosheets. Also, we demonstrate the fabrication of electrochemical capacitors using this film.Figure optionsDownload full-size imageDownload as PowerPoint slide