Harvesting Electricity from Atmospheric Moisture by Engineering an Organic Acid Gradient in Paper

Abstract

Moisture-activated electric generators (MEGs) that harvest clean energy from atmospheric humidity offer exciting opportunities for upgraded energy conversions. However, it is challenging to obtain MEGs that are both easy to fabricate and of high output power, due to the requirement for particular functional materials and the cumbersome manufacturing process. Herein, a simple and general method is adopted to prepare MEGs with chemically gradient structures. As a specific example, a gradient distribution of citric acid was successfully constructed inside an A4 printer paper by asymmetric drying, which can generate a continuous voltage of tens of millivolts by ambient humidity, and even to volts (275 mV and 7.6 μA cm −2 ) under asymmetric humidity stimulation, and the maximum power density output was 2.1 μW cm −2 . The driving force behind this energy conversion is a self-maintained ionic gradient created within the paper by the asymmetric ionization of gradient organic acids when exposed to gradient or nongradient humid air. This work broadens the class of materials and possibilities for the rapid development of MEGs, shedding new light on the revolution of generators that harvest green and sustainable energy for power generation.

Moisture-Enabled Electric Generators Based on Electrospinning Silk Fibroin/Poly(ethylene oxide) Film Impregnated with Gradient-Structured Sericin

“…Two accepted MEGs models are ion concentration gradient diffusion and flow current models. − The ion concentration gradient diffusion model relies on the construction of chemical gradient structures or asymmetric hygroscopicity to drive the directional diffusion of charged ions to generate a potential between both sides of the MEGs architecture. − Studies have revealed that the gradient structure can improve the MEGs performance by affecting the ion concentration difference. A highly flexible dual-asymmetric MEGs based on poly­(vinyl alcohol) (PVA) and cotton fabric was developed .…”