Thermocouple-based passive rectification for energy harvesting from thermal fluctuations

In this work, we show that free-standing graphene membranes can be regarded as a spontaneously formed nonequilibrium ordered structure and may serve as a source of weak, high-frequency electrical signals through capacitive coupling. We propose a passive rectification mechanism based on the asymmetric thermal response of the two junctions of a thermocouple, which enables the conversion of weak alternating currents into a direct-current electromotive force without any threshold voltage. On the basis of this mechanism, a thermocouple-assisted model is developed to harvest vibration-induced electrical energy from suspended graphene films. Furthermore, we discuss the possibility that thermocouple rectifiers operating at the nanoscale may exhibit spontaneous rectification driven solely by thermal noise, suggesting a new perspective on thermoelectric energy conversion.