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

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 degrees 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.