Zwitterionic Copolymeric Bilayer for Moisture-Induced Electrical Energy Generation by Harvesting Atmospheric Water in...

We report a dual-action energy harvester featuring a synergistic copolymeric network designed for efficient atmospheric water harvesting (AWH) and moisture-induced electricity generation. The scientific significance of this work lies in the first-time application of a zwitterionic [2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (DMAPS) and acrylamide (AM) copolymer for AWH. The water-harvesting film is composed of DMAPS and AM, which is dried, soaked in LiCl solution, frozen using liquid nitrogen, and freeze-dried for 24 h to obtain P(DMAPS-co-AM)-LiCl with porous monolithic structure. The energy-harvesting layer is assembled from a P(DMAPS-co-acrylic acid (AA)) copolymer. By incorporating the DMAPS monomer into both layers, we establish a chemically compatible and homologous interface that facilitates efficient ionic transport and minimizes interfacial resistance-a critical advantage for dual-action devices often overlooked in previous studies. Dynamic vapor adsorption measurements demonstrate superior hygroscopicity, with an equilibrium water capacity of 0.873 g/g at 30% RH, which increases to 1.72 g/g at 60% RH. Electrical generation is proposed to arise primarily from the dissociation and directional migration of protons (H+) across the zwitterionic interface, a mechanism supported by cyclic voltammetry analysis. Under an arid condition of 30% RH, the system produces a stable open-circuit voltage of 0.65 V and an average short-circuit current density of 1.15 μA/cm2 for over 2500 min continuously, achieving an energy density of ∼112.1 mJ/cm2 and a maximum power density of 23.4 nW/cm2. As such, this integrated material approach offers a robust and scalable route for autonomous, self-powered systems in low-humidity environments.