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MoS2 Can Be a Energy-efficient Candidate for Water Desalination

Most available desalination technologies rely on a process called reverse osmosis (RO) to push seawater through a membrane in order to produce fresh water. This process has always been plagued by high energy usage and fouling issues.

In new work, reported in ACS Energy Letters, researchers now have shown with molecular dynamics simulations that a nanoporous MoS2 membrane allows a higher water flux compared with other materials such as graphene, boron nitride and phosphorene.

Recent experiment has already shown the viability of laminar MoS2 in practical water desalination applications ("2D nanomaterial reverse osmosis membrane for water desalination"). This new finding indicates that MoS2 can be a much more energy-efficient candidate for water desalination and a potential solution for people living in freshwater-scarce regions of the world.

"In this work, we dug deeply into the physical reasons behind why MoS2 performed better than other two-dimensional materials in water desalination processes," Amir Barati Farimani, an Assistant Professor of Mechanical Engineering at Carnegie Mellon University, tells Nanowerk. "Through molecular dynamics simulation, we found out that water density near a MoS2 membrane is lower compared to that near other materials, which indicates that water molecules were more likely to transport through the membrane instead of accumulating around it."

Farimani's team also discovered that a MoS2 pore, even with the same area as graphene and other 2D materials' pores, generally held more water inside of it and allowed faster transport of water molecules. Most importantly, the scientists calculated that the energy barrier for water molecules to pass MoS2 pores was lower compared with other materials.

These reasons combined lead to higher performance of MoS2 membranes in water desalination processes.

According to the team, the future directions for this research will be to experimentally realize a water desalination process using MoS2 membranes with nanopores. This could also open new opportunities for more applications of MoS2 in areas such as supercapacitance.

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