Spray-Coated Multiwalled Carbon Nanotube Composite Electrodes for Thermal Energy Scavenging Electrochemical Cells

Spray-coated multiwalled carbon nanotube/poly(vinylidene fluoride) (MWCNT/PVDF) composite electrodes, scCNTs, with varying CNT compositions (2 to 70 wt %) are presented for use in a simple thermal energy-scavenging cell (thermocell) based on the ferro/ferricyanide redox couple. Their utility for direct thermal-to-electrical energy conversion is explored at various temperature differentials and cell orientations. Performance is compared to that of buckypaper, a 100% CNT sheet material used as a benchmark electrode in thermocell research. The 30 to 70 wt % scCNT composites give the highest power output by electrode area–seven times greater than buckypaper at ΔT = 50 °C. CNT utilization is drastically enhanced in our electrodes, reaching 1 W gCNT–1 compared to 0.036 W gCNT–1 for buckypaper. Superior performance of our spray-coated electrodes is attributed to both wettability with better use of a large portion of electrochemically active CNTs and minimization of ohmic and thermal contact resistances. Even com...