Ion-engine hydrogel based solar desalination for water-electricity cogeneration with milliampere level current

Abstract

Seawater evaporation-induced electricity generation (SEG) holds potential in alleviating global energy and freshwater demands. However, conventional SEGs suffer from non-selective ion transport in seawater, leading to severe Debye screening effect and low output current (<10 µA). To overcome this bottleneck, we develop an ion-engine hydrogel based solar-powered SEG (SSEG), achieving milliampere level peak current of 1.2 mA from seawater due to molecular-level ion control, surpassing previously reported SEGs by 1 to 2 orders of magnitude. Molecular dynamics simulations and Hittorf’s method confirm that the hydrogel dramatically enhances anion transference number (~0.83) while suppresses cation-induced Debye screening via chemical gating, which is attributed to synergistic effect of metal-polymer coordination and ion-preferential association. The integrated SSEG system operating outdoors can generate power up to 24 mW, sufficient to charge small electronics, while producing freshwater at a high-yield over 2.0 kg m-2 h-1. Additionally, the ion modulation mechanism boosts the regeneration potential of waste concentrated by-products in SSEG systems, enabling the recovery of up to 16.7 W m-2 of blue energy through reverse electrodialysis, improving sustainability and economic value. This work demonstrates an approach for developing off-grid integrated water-energy cogeneration systems.