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Scalable, inexpensive, one-pot, facile synthesis of crystalline two-dimensional birnessite flakes
Journal article   Open access   Peer reviewed

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

Hussein O. Badr, Kiana Montazeri, Tarek El-Melegy, Varun Natu, Michael Carey, Ramchandra Gawas, Phu Phan, Qian Qian, Christopher Y. Li, Ulf Wiedwald, …
Matter
Jun 2022
url
https://doi.org/10.1016/j.matt.2022.05.038View
Published, Version of Record (VoR)Open Access (Publisher-Specific) Open

Abstract

2D flakes birnessite bottom-up electrocatalysis layered manganese oxide tetramethylammonium hydroxide
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 bottom-up approach—5 different water-insoluble Mn-bearing precursors, viz. Mn3O4, Mn2O3, MnB, Mn5SiB2, and Mn2AlB2, into birnessite-based 2D flakes that, in some cases, are remarkably crystalline. The precursor powders are immersed in 25 wt % tetramethylammonium hydroxide aqueous solutions at 50°C to 80°C 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 O2 electrocatalysis with activities comparable with those of a commercial Pt/C catalyst. [Display omitted] •Scalable, inexpensive, one-pot, facile synthesis of 2D birnessite flakes•Near-ambient conversion of water-insoluble, non-layered Mn-precursors•Resulting birnessite flakes are crystalline, with thicknesses around ≈2 ± 0.4 nm•Reversible O2 electrocatalysis with activities comparable with those of a Pt/C catalyst Typically, materials that are atomically thick but extend over large areas are labeled two-dimensional (2D) materials, which are produced by exfoliating or etching layered bulk materials. The process can be slow and hazardous and can render the production of 2D materials in large quantities challenging and expensive. We developed a one-pot recipe of producing 2D sheets in bulk scale almost at room temperature, starting with inexpensive green precursors. The quality of sheets produced is as high as those prepared using high temperatures and pressures and/or hazardous chemicals. Our one-pot method is thus the simpler, scalable, cheaper, and safer approach. Electrodes made with our materials could lead to better batteries for cell phones and transportation. The sheets are also biocompatible, which renders them good candidates for use in the biomedical field. This discovery is a true breakthrough in scaling up the production of nanomaterials and will have a direct and positive impact on society. Two-dimensional materials are usually prepared using special chemicals and higher temperature processes and/or using hazardous chemicals such as hydrofluoric acid. Herein, we present a near-ambient condition (50° to 80°C), non-toxic, one-pot, cheap, scalable pathway to convert five different water-insoluble, non-layered Mn-containing precursors, viz. Mn3O4, Mn2O3, MnB, Mn5SiB2, and Mn2AlB2, into 2D crystalline birnessite flakes. The resulting flakes demonstrated electrocatalytic activities for reversible O2 reactions that are comparable with Pt/C electrodes.

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Collaboration types
Domestic collaboration
International collaboration
Web of Science research areas
Materials Science, Multidisciplinary
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