Ultrahigh thermopower waves in carbon nanotube‐antimony telluride composites enabled by thermal decomposition of formaldehyde

Scattered energy sources are essential to advance sustainable systems with the development of small-sized devices. Thermopower waves (TWs), which use self-propagating combustion along micro-nanostructured composites, can directly convert thermochemical to electrical energy, thereby resolving the configuration limits in small dimensions. However, poor sustainability and energy density, induced by short duration of the combustion should be addressed, although TWs exhibit high-power densities. Herein, we report the use of formaldehyde (FA)-activated multi-walled carbon nanotube (MWCNT) and Sb2Te3 composites to achieve ultrahigh TWs enabled by the remarkable enhancement of the sustained time and the chemical energy conversion. The FA supports sustained and amplified TWs through its chemical reaction pathways, while the MWCNTs and Sb2Te3 serves as thermal conduits and thermoelectric materials to generate TWs. The weight ratio of MWCNT and Sb2Te3 was optimized to produce a high-power density (similar to 1.1 mW/cm(2)), and the optimal amount of FA to the tuned MWCNT:Sb2Te3 ratio resulted in a significantly sustained time (68.55 seconds, 2698% enhancement compared to without FA). The pre-decomposed carbon oxides and carbonate from the FA chemical reaction considerably delay self-propagating reaction and promoted the evaporation of the Te species in Sb2Te3 and its oxidation to Sb2O3 and Sb2O5, which could produce additional energy generation (similar to 0.29 mJ/cm(2)). A theoretical analysis elucidated the individual contributions of the Seebeck and chemical energy, and rational strategies to enhance the TWs. This work can pave the way for the development of advanced TW devices that satisfy the demands for both high energy density as well as long-term power generation.