Understanding the chemical-thermal-electrical energy conversion in micro/nanostructures is crucial for making breakthroughs in new fields related to energy research, as well as in improving the existing energy technologies. Thermopower wave utilizing this chemical-thermal-electrical energy conversion in hybrid structures of nanomaterials and combustible fuel has recently attracted much attention as an enhanced combustion wave with the concomitant voltage generation. In this study, we have explored thermopower waves in the hybrid composite of the chemical fuel and surface-oxidized copper submicroparticles (SCuMPs) films during combustion. Here, we have demonstrated that the manipulations of micro/nanostructures in SCuMPs films by annealing are capable of converting the energy released during chemical combustion to a significantly large amount of thermal and electrical energy (average combustion velocity 32.6 mm s À1 , output voltages up to 6.2 V; average 2.02 V) in comparison with the as-prepared SCuMPs films (19.2 mm s À1 , up to 1.0 V; average 0.75 V) from thermopower waves. Owing to the inter grain boundary fusions and inner/surface nanowire-bonding by annealing, the chemical combustion rate, the corresponding thermal transport, and the electrical energy generation were greatly enhanced in the micro/nanostructured films. This work can contribute to the enhanced combustion wave and voltage generation in thermopower waves as well as further understanding of the fundamental phenomena in chemical-thermal-electrical energy conversions using micro/nanostructured materials.

Structure-guided combustion waves transform MnO2 nanoparticles into core–shell nanostructures of reduced manganese oxides and carbon layer for high performance supercapacitors.

Core-shell nanostructures of metal oxides and carbon-based materials have emerged as outstanding electrode materials for supercapacitors and batteries. However, their synthesis requires complex procedures that incur high costs and long processing times. Herein, a new route is proposed for synthesizing triple-core-shell nanoparticles of TiO @MnO @C using structure-guided combustion waves (SGCWs), which originate from incomplete combustion inside chemical-fuel-wrapped nanostructures, and their application in supercapacitor electrodes. SGCWs transform TiO to TiO @C and TiO @MnO to TiO @MnO @C via the incompletely combusted carbonaceous fuels under an open-air atmosphere, in seconds. The synthesized carbon layers act as templates for MnO shells in TiO @C and organic shells of TiO @MnO @C. The TiO @MnO @C-based electrodes exhibit a greater specific capacitance (488 F g at 5 mV s ) and capacitance retention (97.4% after 10 000 cycles at 1.0 V s ), while the absence of MnO and carbon shells reveals a severe degradation in the specific capacitance and capacitance retention. Because the core-TiO nanoparticles and carbon shell prevent the deformation of the inner and outer sides of the MnO shell, the nanostructures of the TiO @MnO @C are preserved despite the long-term cycling, giving the superior performance. This SGCW-driven fabrication enables the scalable synthesis of multiple-core-shell structures applicable to diverse electrochemical applications.

No abstract

No abstract