A vasculatural hydrogel combined with Prussian blue for solar-driven vapor generation?

Journal of Materials Chemistry A Pub Date: 2022-05-16 DOI: 10.1039/D2TA02348B

Abstract

Solar-driven clean water production presents unique merits of sustainability and environmental friendliness. Tremendous efforts have been devoted to the preparation of solar-driven vapor generators (SVGs) with timely water transport and/or excellent light-trapping properties. Herein, an efficient SVG is achieved by the combination of polyvinyl alcohol (PVA) hydrogel and Prussian blue (PB), with a unique vasculature obtained through techniques of a directional freezing and salting-out strategy. Thermodynamic calculations indicate that the water in this SVG system has lower vaporization enthalpy (1126.9 J g?1) than bulk water (2460.0 J g?1), which can be attributed to the high content of weakly hydrogen-bonded water in the PVA fibers. Moreover, both the experimental and theoretical analyses demonstrate that the vertically arranged channels existing in the SVG ensure rapid water transport (1.6 cm min?1) and light-trapping capacities. Benefitting from the above factors, the SVG exhibits a freshwater production rate of 3.44 ± 0.17 kg m?2 h?1 under 1 sun (1 kW m?2) irradiation with a photothermal conversion efficiency of up to 95% in 3.5% NaCl brine, reaching the theoretical ceiling of PVA-based materials. Additionally, it can work in practical environments for a long time without performance degradation, which is usually caused by salt scaling and biological fouling. This new kind of vasculatural hydrogel-based SVG is a competitive candidate for solar-driven clean water production, thus satisfying the growing demand for clean and safe drinking water.

Graphical abstract: A vasculatural hydrogel combined with Prussian blue for solar-driven vapor generation
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