Advanced Thermopower Wave in Novel ZnO Nanostructures/Fuel Composite

Abstract

Thermopower wave is a new concept of energy conversion from chemical to thermal to electrical energy, produced from the chemical reaction in well-designed hybrid structures between nanomaterials and combustible fuels. The enhancement and optimization of energy generation is essential to make it useful for future applications. In this study, we demonstrate that simple solution-based synthesized zinc oxide (ZnO) nanostructures, such as nanorods and nanoparticles are capable of generating high output voltage from thermopower waves. In particular, an astonishing improvement in the output voltage (up to 3 V; average 2.3 V) was achieved in a ZnO nanorods-based composite film with a solid fuel (collodion, 5% nitrocellulose), which generated an exothermic chemical reaction. Detailed analyses of thermopower waves in ZnO nanorods- and cube-like nanoparticles-based hybrid composites have been reported in which nanostructures, output voltage profile, wave propagation velocities, and surface temperature have been characterized. The average combustion velocities for a ZnO nanorods/fuel and a ZnO cube-like nanoparticles/fuel composites were 40.3 and 30.0 mm/s, while the average output voltages for these composites were 2.3 and 1.73 V. The high output voltage was attributed to the amplified temperature in intermixed composite of ZnO nanostructures and fuel due to the confined diffusive heat transfer in nanostructures. Moreover, the extended interfacial areas between ZnO nanorods and fuel induced large amplification in the dynamic change of the chemical potential, and it resulted in the enhanced output voltage. The differences of reaction velocity and the output voltage between ZnO nanorods- and ZnO cube-like nanoparticles-based composites were attributed to variations in electron mobility and grain boundary, as well as thermal conductivities of ZnO nanorods and particles. Understanding this astonishing increase and the variation of the output voltage and reaction velocity, precise ZnO nanostructures, will help in formulating specific strategies for obtaining enhanced energy generation from thermopower waves.

Phase Transformations of Cobalt Oxides in CoxOy-ZnO Multipod Nanostructures via Combustion from Thermopower Waves

“…The 180 °C lower temperature in this case might have been due to the fast decomposition and heat loss, which were induced by the absence of Co x O y –ZnO films. On the other hand, the temperature of only the ZnO/fuel films was about 870 °C in diverse structures . The Co 3 O 4 –ZnO multipod/fuel composite films produced a higher maximum temperature probably because the released oxygen from the phase transition from Co 3 O 4 –ZnO to CoO–ZnO 1− x was supplied to the chemical reaction in the combustion waves.…”

“…On the other hand, the temperature of only the ZnO/fuel fi lms was about 870 °C in diverse structures. [ 23 ] The Co 3 O 4 -ZnO multipod/fuel composite fi lms produced a higher maximum temperature probably because the released oxygen from the phase transition from Co 3 O 4 -ZnO to CoO-ZnO 1− x was supplied to the chemical reaction in the combustion waves. The measured surface temperature was mostly in the range of 600 °C-1000 °C, indicating a chemical transition caused by the release of oxygen molecules (R3), as measured by TGA (Figure 7 a).…”

The X-ray photoelectron spectroscopy and high-temperature structural studies of Zn1−xNixO/NiO two-phase composites

“…Lee et al. recently demonstrated that ZnO nanostructures, such as nanorods and nanoparticles are capable of generating high‐output voltage (3 V) from thermopower waves (i.e., the energy conversion from chemical energy to thermal energy which in turn converted to electrical energy) (). Athauda et al.…”

“…demonstrated that ZnO nanostructures, such as nanorods and nanoparticles are capable of generating high-output voltage (∼3 V) from thermopower waves (i.e., the energy conversion from chemical energy to thermal energy which in turn converted to electrical energy) [9]. Athauda et al reported that the one-dimensional hierarchical composite materials based on ZnO nanowires and electrospun blend nanofibers can act like highly effective photocatalysts [10].…”

Giant Peak Voltage of Thermopower Waves Driven by the Chemical Potential Gradient of Single‐Crystalline Bi2Te3

“…Materials with greater Seebeck coefficients were investigated as substrates because the low Seebeck coefficient (≈80 µV K −1 ) of MWNTs was regarded as a hurdle to increase electrical potential of thermopower waves . These include Bi 2 Te 3 (≈−287 µV K −1 ), Sb 2 Te 3 (≈243 µV K −1 ), ZnO (≈−360 µV K −1 ), MnO 2 (≈−1900 µV K −1 ), and Cu–CuO–Cu 2 O powders (≈10 000 µV K −1 ) . The effect of chemical composition of fuel on thermopower waves was also explored .…”