Facile one-pot transformation using structure-guided combustion waves of micro-nanostructured beta-Bi2O3 to alpha-Bi2O3@C and analysis of electrochemical capacitance

Abstract

Precise phase-transformation can facilitate control of the properties of various materials, while an organic coating surrounding inorganic materials can yield useful characteristics. Herein, we demonstrate facile, selective manipulation of micro-nanostructured bismuth oxide (Bi2O3) for phase transformation from microflower-like beta-Bi2O3 to micropill-like alpha-Bi2O3, with carbon-coating layer deposition, using structure-guided combustion waves (SGCWs). Microflower-like. alpha-Bi2O3 are synthesized as core materials and nitrocellulose is coated on their surfaces for the formation of core-shell hybrid structures of Bi2O3 and chemical fuel. The SGCWs, which propagate along the core-material and fuel interfaces, apply high thermal energy (550-600 degrees C) and deposit incompletely combusted carbonaceous fuel on the microflower-like beta-Bi2O3 to enable transformation to alpha-phase and carbon-coating-layer synthesis. SGCW-induced improvements to the electrochemical characteristics of the developed micropill-like alpha-Bi2O3@C, compared with the microflower-like beta-Bi2O3, are investigated. The enhanced stability from the alpha-phase Bi2O3 and micropill-like structures during charge-discharge cycling improves the specific capacitance, while the carbon-coating layers facilitate increased electrical conductivity. SGCW-based methods exhibit high potential for selective phase manipulation and synthesis of carbon coatings surrounding micro-nanomaterials. They constitute a low-cost, fast, large-scale process for metal oxides, ceramics, and hybrid materials, implemented through control of the processing parameters by tuning the temperature, chemical fuel, and ambient conditions. (C) 2017 Elsevier B.V. All rights reserved.