# Ice-Templated Zwitterionic Sponge Hydrogels for Stable and Efficient Solar Desalination in High-Salinity Brines

## TL;DR

A new hydrogel material is developed for solar desalination that works efficiently even in highly salty water.

## Contribution

A zwitterionic sponge hydrogel is fabricated using ice-templated polymerization to enable stable and efficient solar desalination in high-salinity brines.

## Key findings

- The hydrogel achieves a high evaporation rate of 1.93 kg m–2 h–1 with 95.1% efficiency under 1 sun irradiation.
- It maintains stable performance in brines up to 10 wt % NaCl.
- Field tests show it produces 12.35 kg m–2 day–1 of freshwater meeting WHO standards.

## Abstract

Solar-driven steam
generation (SSG) offers a sustainable
pathway
for desalination, yet achieving temperature-regulated control over
macroporous structures in salt-tolerant hydrogels remains a critical
challenge. Here, we report a carbon black-coated PDMAPS sponge hydrogel
(PDMAPS-CB-SH) fabricated via an ice-templated polymerization strategy,
where the pore size and connectivity are tuned by regulating ice-crystal
growth at different prefreezing temperatures. The optimized PDMAPS-CB-SH
integrates abundant interconnected pores with the intrinsic antipolyelectrolyte
effect of zwitterionic networks, enabling rapid water transport and
stable swelling in brines up to 10 wt % NaCl. Upon incorporation of
carbon black nanoparticles, the hydrogel evaporator achieves a high
evaporation rate of 1.93 kg m–2 h–1 with an efficiency of 95.1% in seawater under 1 sun irradiation
(1.0 kW m–2), and maintains stable evaporation performance
under the tested high-salinity condition. Outdoor field tests further
confirm its scalability, delivering 12.35 kg m–2 day–1 of freshwater with condensate quality meeting
WHO drinking-water standards. This work establishes ice-templated
zwitterionic sponge hydrogels as a versatile and scalable platform
for efficient solar desalination, particularly under challenging high-salinity
conditions.