Journal article
Deciphering the Atomic Patterns Leading to MnO2 Polymorphism
Chem, v 5(7), pp 1793-1805
11 Jul 2019
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
A fundamental understanding of phase transition mechanisms for polymorphic materials is the prerequisite for developing rational synthesis strategies toward phase homogeneity. Here, we target polymorphic MnO2 as the prototype system and reveal the atomic mechanisms governing the phase selection among various MnO2 tunnel structures that are hydrothermally synthesized from a layered MnO2 precursor. A topotactic layer-to-tunnel (L-T) transition mechanism featuring solid-state Mn migration and structure rearrangement is discovered. The transition exhibits multi-step kinetics with the formation of intermediate large tunnels, which introduces structural complexity into the end product with significant phase and compositional heterogeneity within single MnO2 particles. Localized valence analysis further reveals the significant effect of Jahn-Teller Mn3+ ordering on the L-T transition kinetics. We expect these findings to assist the understanding of polymorphism evolution and be further applied to rationalize material synthesis strategies toward phase homogeneity and to establish an accurate synthesis-structure relationship.
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•MnO2 polymorphism originates from a multi-step layer-to-tunnel transition process•Layer-to-tunnel transition mechanism is explored with atomic resolution•Ordering of intralayer Jahn-Teller active Mn3+ determines as-formed tunnel phases
Historically long applied in our ever-growing industry, polymorphic manganese dioxide (MnO2) has attracted extensive research interest on the origins and evolution of material polymorphism and its critical role in determining material phase purity. Despite significant progress, the mechanism accounting for the formation of polymorphic MnO2 structures, particularly the tunnel-based phases, has remained rudimentary. Here, we investigate the atomic-level mechanisms dominating the formation of polymorphic tunnel phases in MnO2 nanomaterials, where a multi-step layer-to-tunnel transition process is identified. Findings of this work will assist the understanding of material polymorphism evolution and can be further applied to rationalize the synthesis strategies of polymorphic materials toward high phase purity.
The mysterious phase transitioning process leading to MnO2 polymorphism is understood with step-by-step reaction kinetics inside a hydrothermal solution being revealed. A layer-to-tunnel transition mechanism is disclosed at the single-atom resolution. Such transition is driven by the release of intralayer strain generated by the agglomeration of Jahn-Teller active [Mn3+O6] octahedra and proceeds via short-range Mn mass transport, leading to the formation of different tunnel phases. Rooted on these fundamental insights, strategies for controlling the synthesis of polymorphic materials are thus provided.
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Details
- Title
- Deciphering the Atomic Patterns Leading to MnO2 Polymorphism
- Creators
- Yifei Yuan - Argonne National LaboratoryKun He - University of Illinois at ChicagoBryan W. Byles - Drexel UniversityCong Liu - Argonne National LaboratoryKhalil Amine - Argonne National LaboratoryJun Lu - Argonne National LaboratoryEkaterina Pomerantseva - Drexel UniversityReza Shahbazian-Yassar - University of Illinois at Chicago
- Publication Details
- Chem, v 5(7), pp 1793-1805
- Publisher
- Elsevier
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Materials Science and Engineering
- Web of Science ID
- WOS:000476612700009
- Scopus ID
- 2-s2.0-85068260777
- Other Identifier
- 991019168464504721
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- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Chemistry, Multidisciplinary