Photothermal-Responsive Aerogel-Hydrogel Binary System for Efficient Water Purification and All-Weather Hydrovoltaic Generation.

Abstract

Hydrovoltaic generators (HVGs) convert abundant water energy into distributed electricity to promote the Internet of Things. Realizing low-cost yet high-performance HVG remains challenging, hindering its commercialization and application. Inspired by the xylem conduits in plants, which transport water and nutrients, an aerogel-hydrogel binary-component system (SHA-HVG) is developed. It consists of a photothermal graphite-doped polyvinylidene fluoride (G-PVDF) aerogel, infilled with a thermosensitive wettability-switchable sulfonic acid-modified polyisopropylacrylamide hydrogel (S-PNIPAM) by in situ polymerization, which significantly promotes water/ion transporting and boosts electricity output. SHA-HVG demonstrates all-weather high output by cooperating power generation mechanisms of thermosensitive hydrogel-promoted surface photothermal evaporation during the daytime and sulfonic group-enhanced ion concentration gradient at nighttime, resulting in efficient water desalination (2.75 kg m^-2 h^-1) and a 2669% increase in power density (56.86 µW cm^-2) compared to single-component HVG of G-PVDF. SHA-HVG is chemically stable and can be reactivated/recycled to improve its power generation efficiency to ∼130% by increasing its built-in ionic environment. A marine/offshore cultivation system is demonstrated using an SHA-HVG array, realizing an autonomous greenhouse for water desalination, self-irrigation, and self-powered environment monitoring. This work presents a cost-effective HVG strategy for efficient seawater desalination and electricity harvesting, envisioning the development of distributed energy, smart agriculture, and offshore planting.