Scalable, inexpensive, one-pot, facile synthesis of crystalline two-dimensional birnessite flakes

Synthesis of two-dimensional (2D) materials that is readily scalable, cost-effective, and eco-friendly is important from both scientific and industrial viewpoints. Currently, these 2D materials are synthesized either by selective etching of relatively expensive layered solids, viz. using a top-down approach, or by autoclaving metal salts/organic compounds. Herein, we describe a near-ambient, one-pot, inexpensive, scalable pathway to convert-through a bot-tom-up approach-5 different water-insoluble Mn-bearing precursors, viz. Mn3O4, Mn2O3, MnB, Mn5SiB2, and Mn2AlB2, into birnes-site-based 2D flakes that, in some cases, are remarkably crystalline. The precursor powders are immersed in 25 wt % tetra-methylammonium hydroxide aqueous solutions at 50? to 80? for 2 to 4 days. The structures, compositions, oxidation states, and morphologies of the synthesized flakes are determined using a battery of characterization techniques. The synthesized 2D sheets demonstrate reversible O-2 electrocatalysis with activities comparable with those of a commercial Pt/C catalyst.

Automated summary

Researchers have successfully synthesized high-quality two-dimensional flakes using a new method that is simple and cost-effective. By converting water-insoluble Mn-bearing precursors into birnesite-based materials, they have achieved remarkable crystallinity for the synthesized flakes.