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Environmentally Friendly γ‐MnO 2 Hexagon‐Based Nanoarchitectures: Structural Understanding and Their Energy‐Saving Applications
Author(s) -
Wu Changzheng,
Xie Wei,
Zhang Miao,
Bai Liangfei,
Yang Jinlong,
Xie Yi
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801814
Subject(s) - pyrolusite , materials science , environmentally friendly , lattice energy , metastability , crystal structure , lattice (music) , phase (matter) , nanotechnology , chemical physics , crystallography , chemistry , manganese , metallurgy , physics , ecology , organic chemistry , biology , acoustics
Although about 200,000 metric tons of γ‐MnO 2 are used annually worldwide for industrial applications, the γ‐MnO 2 structure is still known to possess a highly ambiguous crystal lattice. To better understand the γ‐MnO 2 atomic structure, hexagon‐based nanoarchitectures were successfully synthesized and used to elucidate its internal structure for the present work. The structural analysis results, obtained from the hexagon‐based nanoarchitectures, clearly show the coexistence of akhtenskite ( ε ‐MnO 2 ), pyrolusite (β‐MnO 2 ), and ramsdellite in the so‐called γ‐MnO 2 phase and verified the heterogeneous phase assembly of the γ‐MnO 2 state, which violates the well‐known “De Wolff” model and derivative models, but partially accords with Heuer's results. Furthermore, heterogeneous γ‐MnO 2 assembly was found to be a metastable structure under hydrothermal conditions, and the individual components of the heterogeneous γ‐MnO 2 system have structural similarities and a high lattice matches with pyrolusite (β‐MnO 2 ). The as‐obtained γ‐MnO 2 nanoarchitectures are nontoxic and environmentally friendly, and the application of such nanoarchitectures as support matrices successfully mitigates the common problems for phase‐change materials of inorganic salts, such as phase separation and supercooling‐effects, thereby showing prospect in energy‐saving applications in future “smart‐house” systems.