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Nano Research

Article Title

Energy-driven surface evolution in beta-MnO2 structures

Authors

Wentao Yao, Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, Michigan 49931, USA
Yifei Yuan, Chemical Science and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA Department of Mechanical and Industrial Engineering, The University of Illinois at Chicago, Chicago, Illinois 60607, USA
Hasti Asayesh-Ardakani, Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, Michigan 49931, USA
Zhennan Huang, Department of Mechanical and Industrial Engineering, The University of Illinois at Chicago, Chicago, Illinois 60607, USA
Fei Long, Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, Michigan 49931, USA
Craig R. Friedrich, Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, Michigan 49931, USA
Khalil Amine, Chemical Science and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
Jun Lu, Chemical Science and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
Reza Shahbazian-Yassar, Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, Michigan 49931, USA Department of Mechanical and Industrial Engineering, The University of Illinois at Chicago, Chicago, Illinois 60607, USA

Keywords

manganese oxide, facet evolution, oriented attachment, growth mechanism, surface energy

Abstract

ABSTRACT Exposed crystal facets directly affect the electrochemical/catalytic performance of MnO2 materials during their applications in supercapacitors, rechargeable batteries, and fuel cells. Currently, the facet-controlled synthesis of MnO2 is facing serious challenges due to the lack of an in-depth understanding of their surface evolution mechanisms. Here, combining aberration-corrected scanning transmission electron microscopy (STEM) and high-resolution TEM, we revealed a mutual energy-driven mechanism between beta-MnO2 nanowires and microstructures that dominated the evolution of the lateral facets in both structures. The evolution of the lateral surfaces followed the elimination of the {100} facets and increased the occupancy of {110} facets with the increase in hydrothermal retention time. Both self-growth and oriented attachment along their {100} facets were observed as two different ways to reduce the surface energies of the beta-MnO2 structures. High-density screw dislocations with the 1/2 Burgers vector were generated consequently. The observed surface evolution phenomenon offers guidance for the facet-controlled growth of betaMnO2 materials with high performances for its application in metal-air batteries, fuel cells, supercapacitors, etc.

Graphical Abstract

Publisher

Tsinghua University Press

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