Angstrom-confined electrochemical synthesis of non van der Waals 2D metal oxides

Materials in 2-dimensional (2D) form often show remarkable properties and unexplored scientific phenomena compared to their bulk form. Layered, van der Waals (vdW) materials have an obvious 2D structure, whereas non-vdW materials have no preference to obtain 2D form. This severely limits the number of currently available 2D non-vDW materials. Here, we introduce a straightforward electrochemical method utilizing the angstrom-confinement of laminar reduced graphene oxide (rGO) nanochannels to obtain 2D transition metal oxides (2D-TMO), a class of non-vdW materials. During synthesis the angstrom-confinement provides a thickness limitation, forcing a sub-unit cell growth of 2D-TMO with oxygen and metal vacancies. The resulting flexible sandwich structure of rGO sheets inserted by a porous polycrystalline network of 2D-TMO is created in centimetre scale. Our accessible method for obtaining 2D-TMO holds high promise to yield exciting properties for fundamental science and applications.