Enhanced thermopower wave via nanowire bonding and grain boundary fusion in combustion of fuel/CuO-Cu₂O-Cu hybrid composites

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 sub-microparticles (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^-1, output voltages up to 6.2 V; average 2.02 V) in comparison with the as-prepared SCuMPs films (19.2 mm s^-1, 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.