Thermal–Electric Nanogenerator Based on the Electrokinetic Effect in Porous Carbon Film

Abstract Converting low‐grade thermal energy with small temperature gradient into electricity is challenging due to the low efficiency and high cost. Here, a new type of thermal–electric nanogenerator is reported that utilizes electrokinetic effect for effective harvesting thermal energy. The nanogenerator is based on an evaporation‐driven water flow in porous medium with small temperature gradient. With a piece of porous carbon film and deionized water, a maximum open‐circuit voltage of 0.89 V under a temperature difference of 4.2 °C is obtained, having a corresponding pseudo‐Seebeck coefficient of 210 mV K −1 . The large pseudo‐Seebeck coefficient endows the nanogenerator sufficient power output for powering existing electronics directly. Furthermore, a wearable bracelet nanogenerator utilizing body heat is also demonstrated. The unique properties of such conversion process offer great potential for ultra‐low temperature‐gradient thermal energy recovery, wearable electronics, and self‐powered sensor systems.