Facile and Scalable Fabrication of Surface‐Modified Sponge for Efficient Solar Steam Generation

Abstract

Solar steam generation is a highly promising technology for harvesting solar energy and desalination. Here, a new solar steam generation system is introduced based on a surface‐modified polyurethane sponge with bilayered structures for efficient solar steam generation. The top layer, coated with polydimethylsiloxane‐modified graphite powder, serves as light‐to‐heat conversion layer with a broad optical absorption, whereas the lower part of the sponge acts as a thermal insulator with a low thermal conductivity in the wet state (0.13882 W m−1 K−1). In addition, the strong hydrophobic wettability of the top layer (water contact angle: 148°) enables self‐floating behavior on water, which is beneficial for practical applications. The results show that compared with a silver‐nanoparticle‐doped sponge and an acid‐etched sponge doped with silver nanoparticles the graphite‐modified sponge (GS) exhibits the highest evaporation efficiency of 73.3 % under 1 kW m2 irradiation, which is 2.6 times that of pure water and far higher than that of untreated polyurethane sponge (36.0 %). The GS shows excellent stability, and its evaporation efficiency remains unchanged even after immersion in water for one month. Based on its cost‐efficient, simple, and scalable manufacturing process, excellent mechanical stability, and high recyclability, the GS shows great potential as an efficient photothermal material for a wide range of large‐scale applications such as solar steam generation, light absorption, heat localization, and seawater desalination.

Reduced Graphene Oxide Coated Hollow Polyester Fibers for Efficient Solar Steam Generation

“…The energy conversion efficiency was found to be 81.3% for rGO‐wrapped HPFs and 73.1% for rGO‐wrapped natural fibers under 1 kW m −2 illumination. With these values, the efficiency of rGO‐wrapped fibers can compete with that of those recently reported porous photothermal materials for efficient solar steam generation . It is worth noting that the rGO‐wrapped HPFs show relatively higher energy conversion efficiency than that of the rGO‐wrapped natural fibers, which may be attributed to the relatively lower thermal conductivity.…”

“…GO was synthesized using a modified Hummers’ method as follows: concentrated H 2 SO 4 (69 mL) and preoxidized graphite (1.8 g) were mixed in a three‐neck bottle in an ice bath. Then, KMnO 4 (9.0 g) was added slowly into the mixture system to keep the temperature under 5 °C, stirring for 2 h. The temperature of the mixture system was heated to 38 °C, stirring for 2 h. Deionized water (138 mL) was added cautiously, which allowed the reaction to subside, and the suspension was heated at 98 °C for 15 min.…”

“…Recently, we have developed several kinds of photothermal materials based on conjugated microporous polymers (CMPs) nanotubes, clay, and sponge for efficient solar steam generation. In particular, we found that the unique cylindrical topology of CMPs nanotubes, which can trap air inside the nanotubes, could lower the thermal conductivity.…”

Photothermal Conversion Material Derived from Used Cigarette Filters for Solar Steam Generation

“…Clearly, the rate of steam generation or mass loss of water is highest for RGO‐CF. The evaporation rate was calculated from the slope of the time‐dependent mass change curve . RGO‐CF exhibited the highest evaporation rate of 1.623 kg m −2 h −1 under 1 sun, which is 1.5 and 2.4 times higher than that of GO‐CF (1.082 kg m −2 h −1 ) and CF (0.664 kg m −2 h −1 ), respectively.…”

“…The high evaporation rate of RGO‐CF can be attributed to its large temperature rise, suggesting its excellent ability to convert light into thermal energy for efficient solar steam generation. The energy conversion efficiency η was calculated according to the literature; the calculation is presented in the Supporting Information. As seen in Figure e, the calculated η value of CF is 28.43 % under 1 sun which is much lower than that of GO‐CF and RGO‐CF under the same solar intensity.…”