Synthesis strategies toward improved ordering of [MnO6] octahedra in tunnel structured 2 x 3 and 2 x 4 MnO2

Improved homogeneity of tunnel size in Na-stabilized 2 x 3 and 2 x 4 MnO2 structures was achieved by identifying and controlling critical synthesis parameters. 2 x 3 and 2 x 4 MnO2 tunnel manganese oxide nanowires were obtained by hydrothermal treatment of Na-birnessite, a layered manganese oxide that undergoes a layer-to-tunnel transition under high pressure and temperature. Herein, the improved ordering of [MnO6] octahedra is revealed via a combined analysis of X-ray diffraction patterns and scanning transmission electron microscopy images. We show that crystallinity of the Na-birnessite precursor and the chemical composition of the system during hydrothermal treatment are crucial for achieving the targeted size of the structural tunnels with adequate uniformity. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Improvements in the homogeneity of tunnel size in Na-stabilized 2 x 3 and 2 x 4 MnO2 structures were achieved by identifying and controlling critical synthesis parameters. Enhanced ordering of [MnO6] octahedra was revealed through a combined analysis of X-ray diffraction patterns and scanning transmission electron microscopy images. It was found that the crystallinity of the Na-birnessite precursor and the chemical composition of the system during hydrothermal treatment are crucial for achieving the targeted size of the structural tunnels with adequate uniformity.