Self-contained Janus Aerogel with Antifouling and Salt-Rejecting Properties for Stable Solar Evaporation

Abstract

Janus structural interfacial vaporization by separating the solar absorber from the bulk working fluid has attracted tremendous attention due to its low heat losses and high solar conversion efficiency for desalination, water purification, energy generation, etc. However, a totally separated double-deck structure with a discontinuous interfacial transition and inefficient photothermic materials undermines its long-term use and large-scale practical exploitation. Herein, a low-cost Janus monolithic chitosan aerogel with continuous aligned run-through microchannels has been demonstrated to have a highly efficient photothermic effect on seawater desalination and wastewater purification. The top solar absorber layer enhances broadband light absorption and photothermal conversion efficiency via the multiple internal reflection of incident light in the aligned microchannels. Moreover, the insulating/hydrophilic bottom layer promotes water transportation and heat localization, and simultaneously prevents salt/fouling accumulation. As a result, a long-term solar vaporization rate of ∼1.76 kg m −2 h −1 is achieved, corresponding to a light-to-vapor efficiency of ∼91% under 1 sun irradiation. Notably, the large-vessel microchannels throughout the aerogel and favorable swelling property provide sufficient water replenishment and storage for completely isolating self-contained evaporation, illustrating an enhanced and time-extended selfcontained solar steam generation. Such a low-cost bilayer aerogel with remarkable cycling stability in various fluids offers potential opportunities for freshwater production in remote rural areas.

Recent developments of hydrogel based solar water purification technology

“…Carbon-based materials have been used as solar absorbers in various studies in recent years, owing to their excellent light absorption over a broad spectrum, ease of preparation, abundance and low cost. Carbon-based materials include activated carbon, 83–86 polymer 76,87–90 or biomass 82,91–95 derived carbide, carbon black 96–101 and various amorphous carbon materials and highly graphitized carbon materials, such as graphene, 56,59,63,74,77,102–122 carbon nanotubes (CNTs) 27,123–130 and their derivatives.…”

“…This study thus proved its higher energy conversion efficiency compared with the evaporator with evenly distributed solar absorbers. In addition, there are some other methods to confine the solar absorbers on the surface layer, such as using the difference in surface tension between ethanol and water, 134 concentrating them on one end of the hydrogel under gravity, 82 carbonizing the upper side of the hydrogel, 90,162 and so on.…”

A Stable Bilayer Polypyrrole‐Sorghum Straw Evaporator for Efficient Solar Steam Generation and Desalination

“…Liu et al. [ 34 ] developed a carbonized chitosan aerogel interfacial evaporator that achieves an evaporation rate of about 1.76 kg m −2 h −1 and an evaporation efficiency of about 91.0% under 1 Sun.…”

“…You et al [33] developed a cellulose aerogel from natural wood to act as a solar interfacial evaporator, which can achieve an evaporation rate of 1.40 kg m −2 h −1 , corresponding to an evaporation efficiency of 83.4% under 1 Sun. Liu et al [34] developed a carbonized chitosan aerogel interfacial evaporator that achieves an evaporation rate of about 1.76 kg m −2 h −1 and an evaporation efficiency of about 91.0% under 1 Sun.Among solar interfacial evaporators, interfacial evaporators with bilayer structure are one of the typical types. There are two Solar desalination is one of the most promising technologies for alleviating the shortage of fresh water.…”

“…You et al [33] developed a cellulose aerogel from natural wood to act as a solar interfacial evaporator, which can achieve an evaporation rate of 1.40 kg m −2 h −1 , corresponding to an evaporation efficiency of 83.4% under 1 Sun. Liu et al [34] developed a carbonized chitosan aerogel interfacial evaporator that achieves an evaporation rate of about 1.76 kg m −2 h −1 and an evaporation efficiency of about 91.0% under 1 Sun.…”