Gas Foaming Guided Fabrication of Hydrogel Beads with Controlled Phase and Porous Structure for Durable and Highly Efficient Solar-Powered Water Purification

Abstract

Solar-powered interfacial evaporation has emerged as a reliable and sustainable strategy for clean water production, and accordingly, the rational fabrication of hydrogel-based evaporators has received special attention. The systems with anti-salt accumulation, scalable fabrication and facile use in large areas of water are in urgent need. Herein, MoS2-embedded foam hydrogel beads having hybrid open- and closed-cell structures are constructed via a self-assembly spinning-foaming-crosslinking method. Taking advantage of the internal hierarchical pore structure and spherical surface geometry of hydrogel beads, the assembled “indirect contact” architecture possess efficient in-situ energy utilization strategy, and could induce sufficient Marangoni effect to accelerate water transport and salt ions backflow, leading to prominent salt resistance. Gratifyingly, the improved system achieves an impressive evaporation rate of 3.58 kg m−2 h−1 and photothermal conversion efficiency of 94.7% under one sun illumination, as well as maintain over 3.3 kg m−2 h−1 for 8 cycles (12 h/cycle) even in the 25 wt% brine. As demonstrated by portable solar still prototype, high quality freshwater with production rate of ∼22 L m−2 day-1 was collected. This study offers a viable strategy for developing the ease of scale, flexible of use, cost-effective and sustainable solar water purification system in real-world applications to mitigate clean water shortages.

Keywords: Solar vapor generation, hydrogel beads, Hierarchical structure, Marangoni effect, Desalination