Flexible nanocomposite electrodes with optimized hybrid structure for improved low-grade heat harvest via thermocells

Thermal energy is ubiquitous and constantly generated in nature and society. Thermocells (TECs) represent a promising energy-conversion technology that can directly translate thermal energy into electricity with a large thermopower, thus having attracted considerable attention in recent years. Nevertheless, the use of noble platinum electrodes in TECs has substantially limited their widespread applications, as the scarcity of platinum element increases the cost of materials, and its intrinsic rigidity is not conducive to flexible and wearable applications under heat sources with complex surface geometry. Herein, we propose a facile hybridizing route to constructing flexible electrodes with optimized nanostructures. The flexible composite electrode is fabricated by decorating a single-walled carbon nanotube network with conducting polypyrrole nanospheres through controlled electrochemical deposition. With refined interfacial nanostructures, the resultant composite film can facilitate carrier transport/transfer at the electrolyte-electrode interface, and thereby shows superior overall thermoelectrochemical performance to noble platinum electrode. The TEC employing the flexible composite electrodes yields a maximum output power of 2.555 µW under the temperature difference of 30 K, and a device comprising 6 TEC units is assembled to efficiently utilize waste heat and human body heat, revealing the high potential of low-grade heat harvesting.