Scalable salt-templated synthesis of two-dimensional transition metal oxides

Abstract

Two-dimensional atomic crystals, such as two-dimensional oxides, have attracted much attention in energy storage because nearly all of the atoms can be exposed to the electrolyte and involved in redox reactions. However, current strategies are largely limited to intrinsically layered compounds. Here we report a general strategy that uses the surfaces of water-soluble salt crystals as growth templates and is applicable to not only layered compounds but also various transition metal oxides, such as hexagonal-MoO3, MoO2, MnO and hexagonal-WO3. The planar growth is hypothesized to occur via a match between the crystal lattices of the salt and the growing oxide. Restacked two-dimensional hexagonal-MoO3 exhibits high pseudocapacitive performances (for example, 300 F cm−3 in an Al2(SO4)3 electrolyte). The synthesis of various two-dimensional transition metal oxides and the demonstration of high capacitance are expected to enable fundamental studies of dimensionality effects on their properties and facilitate their use in energy storage and other applications.

Self-catalyzed decomposition of discharge products on the oxygen vacancy sites of MoO3 nanosheets for low-overpotential Li-O2 batteries

“…The two strong peaks of the prepared MoO 3 NSs could be well indexed to the (110) and (021) peaks, indicating the highly preferred orientations. Moreover, in contrast to the bulk MoO 3 , the obvious broad peak located around 25°of the exfoliated 2D MoO 3 is in accordance with the results in other works [42]. This interesting broadness may be related to the distorted layer structure in orthorhombic MoO 3 (Fig.…”

Scalable Synthesis of Ultrathin Mn3N2 Exhibiting Room‐Temperature Antiferromagnetism

“…Synthesis of Ultrathin Mn 3 N 2 : A salt-templating method, which was developed previously, [18,20] was used for the synthesis. Typically, 17 mg MnCl 2 ⋅4H 2 O (Sigma-Aldrich, USA) was dissolved in 20 mL ethanol (95%) to form MnCl 2 precursor solution in ethanol.…”

“…Since metal oxides are fairly stable and the formation of TMNs by ammoniation or nitridation always needs high temperatures, instead of the reduction of oxide, we chose manganese chloride as the precursor, which can be directly ammoniated to form 2D metal nitride. [20] The ratio of solution to salt controlled the thickness of the layer (see details in Figure S2 in the Supporting Information and the Supporting Note). The schematic of synthesis of 2D Mn 3 N 2 is shown in Figure 1.…”

“…In the actual synthesis, the transparent MnCl 2 precursor solution was poured into 200 g KCl (Figure 1b), and the MnCl 2 @KCl powder was dried and treated at 750 °C under a constant flow of ammonia. [20] It is worth mentioning that the crystal structures of Mn 3 N 2 and KCl have several features in common. After transformation, the KCl salt template was washed with deionized (DI) water to obtain 2D Mn 3 N 2 (Figure 1e; Figure S3, Supporting Information).…”

Two‐Dimensional Metal Oxide Nanomaterials for Next‐Generation Rechargeable Batteries

“…[9] This generalized bottom-up method provides a pathway for the synthesis of other 2D metal oxide nanomaterials in large quantities. [103] After dissolving the salt-template in water, the obtained 2D nanosheets could be reassembled into a binder-and additivefree film by filtration. Via this approach, TiO 2, ZnO, Co 3 O 4 , and WO 3 nanosheets with widths up to a few tens of micrometers and thicknesses of a few nanometers, corresponding to 2-7 stacking layers of the monolayer, were fabricated.…”