Flexible and Highly Efficient Bilayer Photothermal Paper for Water Desalination and Purification: Self-Floating, Rapid Water Transport, and Localized Heat

Abstract

In view of the sustainable and environmentally friendly characteristics of solar energy, solar water evaporation has been identified as a promising approach to mitigate the global water crises. However, it is still a great challenge to develop a portable, flexible, scalable, and high-performance solar water evaporation material. Herein, a bilayer-structured solar water evaporation material consisting of a top multiwalled carbon nanotube (MWCNT) layer and a bottom polyphenylene sulfide/fibrillated cellulose (PPS/FC) paper was fabricated via a simple vacuum filtration technology for efficient solar water evaporation. The MWCNT layer performs as a light absorber with a high solar absorptance (∼93%) in the wavelength range from 400 to 1200 nm and good light-to-heat conversion capability, while the bottom layer (porous network-structured PPS/FC paper) exhibits excellent water transporting ability, high temperature stability, and good thermal insulating capability (0.0467 W m–1 K–1). Benefiting from the above advantages, an attractive water evaporation rate of 1.34 kg m–2 h–1 was achieved with near ∼95% efficiency under 1 sun irradiation (1 kW m–2). Moreover, the MWCNTs@PPS/FC paper maintains high solar evaporation efficiency after several cycles, indicating long-term durability and good reusability. Moreover, the collected clean water using the MWCNTs@PPS/FC paper from seawater of different salinities, simulated wastewater samples with different pH values or containing heavy metal ions, as well as industrial dyes, satisfy the drinkable water standard (defined by WHO), demonstrating excellent seawater desalination and wastewater purification capability. The advanced performances of the MWCNTs@PPS/FC paper could inspire novel paradigms of solar-driven water evaporation technologies in drinkable water collection.

The gorgeous transformation of paper: from cellulose paper to inorganic paper to 2D paper materials with multifunctional properties

“…79 To the best of our knowledge, the reasons why cellulose-based paper has opportunities to become a supporting platform for solar absorbers for the construction solar evaporators can ascribe to the following points: (1) cellulose paper with high capillary power due to its microporous structure and excellent hydrophilicity can continuously pump water from the bulk to the interface, supporting the successful conversion of water to steam. 8,79 (2) Due to its low thermal conductivity and excellent thermal insulation, cellulose paper a as floater reduces the heat loss to the environment. 80 (3) The abundant functional groups on cellulose paper allow its modification with various photothermal materials for the construction of bilayer structures.…”

“…For example, multiwalled carbon nanotubes (MWCNTs) show remarkable solar absorbance over a wide spectrum range and a high light-to-heat conversion efficiency. 84 Huang et al 8 reported the preparation of a highly efficient bilayer photothermal paper by combining a top multiwalled carbon nanotube (MWCNT) layer and a bottom polyphenylene sulfide/fibrillated cellulose (PPS/FC) paper for water desalination and purification.…”

“…272 In another example, Yu et al 240 constructed RGO-coated cellulose fiber (RGO@CF) paper to adsorb organic dyes for the decolorization of solutions, where organic dyes were employed as pseudocapacitive materials to construct flexible supercapacitors based on dye-modified RGO@CF electrodes. In addition, CNTs as an excellent photothermal material were combined with cellulose paper to fabricate bilayer photothermal paper for water desalination and purification, 8 which has been mentioned in the multifunctional applications of cellulose paper.…”

“…For instance, cellulose paper with a hydrophilic nature can be employed as a substrate material in solar-driven water evaporators, which can quickly transport water to the upper layer for receiving heat energy. 8 Taking advantage of its hygroscopic property, some researchers designed and fabricated humidity sensors. 3,4…”

In situ synthesizing C‐CuO composite for efficient photo‐thermal conversion and its application in solar‐driven interfacial evaporation

“…Steam generation was easily achieved by efficient harvesting of solar energy, which is viewed as a promising approach to obtain freshwater in these water‐stressed areas 5‐8 . Nevertheless, most of existing solar evaporation system is subjected to poor photo‐thermal conversion performance due to the heat dissipation to nonevaporating section by warming bulk water 9‐12 . Intentionally, confining heat to evaporation interface contributes to the escape of the interfacial water molecules from liquid to vapor, 13‐16 ultimately booming the evaporation performance.…”