Interfacial solar desalination is an efficient approach for sustainably handling water scarcity. Finding photothermal materials with effective light absorption and low heat conductivity is challenging.
An investigation of layered bismuth copper oxysulfide (BCSO nanosheets) as a potential photothermal absorber material for interfacial solar desalination was recently reported in a study published in Desalination.
The researchers demonstrated that anisotropic thermal transport is possible by the 2D layered structure of BCSO.
When coated on substrates, the nanosheet morphology causes a nanoporous coating due to a nano-clustering action, resulting in a nano-porosity, rough surface, and significant heat confinement.
Limitations of Conventional Solar Desalination
Owing to its impact on both industrial development and the survival of the human race as a whole, drinking water scarcity has become a global concern. Solar desalination has received more attention to address this issue as a method that permits affordable, sustainable, and energy-efficient freshwater production.
Due to its low photothermal conversion and high heat dissipation, conventional solar desalination performs poorly and cannot meet real-world water demand.
Strategy to Enhance the Performance of Solar Desalination
Interfacial Solar Steam Generation (ISG) can be produced based on improvements in photothermal absorber materials, thermal management, and structural design to improve the performance of traditional solar desalination.
In conventional interfacial heaters, the photothermal absorber transforms solar energy into confined heat energy while the water evaporates in a localized high-temperature zone. Therefore, the porous solar absorber can be allowed to float on the water's surface without intricate pressure management or costly infrastructure, making it simple to apply the ISG.
Promising Photothermal Materials for ISGs
Photothermal materials (PTMs) are essential for ISGs. High photothermal conversion and light absorption efficiency, low thermal conductivity, and superior wettability to maintain a sufficient water supply are necessary to accomplish high water evaporation rates (i.e., steam generation).
Numerous materials can be used as photothermal materials, including metal sulfides, metal oxides, and carbon-based compounds, all of which have improved solar steam generation.
Combining Absorber Materials for Enhanced ISG Performance
PTMs that simultaneously meet all the criteria (high light absorption, low heat conductivity, and good wettability) are still uncommon. Materials with oxides or sulfide bases used in photothermal absorbers frequently have poor stability, a complex synthesis procedure, or high thermal conductivity (>1 W/ mK).
Two different absorber materials can be combined to take advantage of the synergistic advantages of various materials to enhance ISG performance.
Metal Oxychalcogenides as Potential Candidates for Enhanced ISGs
Due to their distinct two-dimensional layered crystal structure, innately low thermal conductivity, tuneable band structure, and long-term environmental stability, metal oxychalcogenides have been recognized as potential materials for thermoelectric and optoelectronic applications.
BiCuSeO (BSCO) is an appealing thermoelectric material made up of layers of insulating (Bi2O2)2+ and alternatively stacked conductive (Cu2Se2)2- that exhibits low thermal conductivity (0.98 W/mK at 293 K) and high Seebeck coefficient for thermoelectric devices.
Synthesis of BCSO Nanosheets as Efficient Photothermal Material
Layered oxychalcogenides of BCSO nanosheets were synthesized by Shridharan et al. and employed as a novel photothermal material for effective solar steam generation. The researchers examined the layered crystal structure, light absorption, thermal conductivity, and wettability of BCSO nanosheets. A porous polyurethane sponge was combined with a solar steam generating system using capillary action and a one-dimensional water channel.
Layered oxychalcogenides of BCSO are a promising photothermal absorber material for effective interfacial solar desalination.
Using a simple hydrothermal process, BCSO nanosheets with dimensions of thickness of 12 nm and lateral length of 100 nm were effectively created.
Layered oxychalcogenides of BCSO nanosheets show excellent photothermal conversion, low thermal conductivity (0.099 W/ mK), excellent wettability, and substantial light absorption in the UV-Vis-NIR range (1040 nm).
With a steady water supply and porous PU substrate, the 1-D water path system achieved a fantastic water evaporation rate of 1.77 kg/ m2 h with a steam production efficiency of 96%.
Even after 10 hours of nonstop evaporation, the BCSO nanosheets' long-term performance remained unaffected. BCSO also demonstrated strong water purification performance and outstanding ion rejection capabilities, which align with the WHO-recommended drinking water standards.
Due to their simple synthesis processes, high light absorption, and low thermal conductivity, oxychalcogenide materials present a viable platform for creating high-performance solar desalination systems that are both affordable and efficient.
Shridharan, T. S., Kang, M. J., Sivanantham, A., Kim, S., & Cho, I. S. (2022). Layered bismuth copper oxychalcogenides as advanced photothermal materials for efficient interfacial solar desalination. Desalination, 540, 115984. https://www.sciencedirect.com/science/article/pii/S0011916422004398
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