Sustainable power generation for at least one month from ambient humidity using unique nanofluidic diode

Abstract

The continuous energy-harvesting of humidity naturally present in air is attractive for the development of clean energy source for self-sustained systems. Controlling the transport of ionized mobile charge in intelligent nanoporous membrane systems is a promising strategy to convert ambient moisture energy to electricity. However, existing designs still suffer from low output power density. Moreover, these devices can only produce short-term (mostly a few seconds or a few hours, rarely for a few days) voltage and current output in the ambient environment. Effort devoted to pursuing membrane materials with new sustained energy conversion mechanism is urgently needed. Here, we design an ionic diode–type hybrid membrane with carbon nanotube/anodized aluminum asymmetric structure capable of continuously harvesting moisture energy in the ambient environment. Under electric fields, a hybrid membrane exhibits ionic current rectification properties, enabling high energy conversion efficiency in the long run due to steady-state one-way ion transport. Using a synergy between the ion rectification of nanofluidic diode and the built-in electric field induced ionization and charge transfer, one single unit produces a sustained maximum open-circuit-voltage, short-circuit-current, short-circuit-current density, output power density of 1.1V, 7.7µA, 11.3µAcm−2 and 1.3µWcm−2/277µWcm−3, respectively (93% RH, 25℃). Besides, the strong hydrogen bonds and van der Waals forces formed at the interface of asymmetric structure make the hybrid membrane robust in humid environment. In particular, the strategy of adjusting the moisture-based energy-harvesting performance based on the rectification effect of the nanofluidic diode is reported for the first time. Compared with the relevant existing devices, those elaborated by the present work show the longest service life and can generate continuous voltage and current for at least one month, demonstrating the feasibility of long-term power generation in any location with moisture conditions.