Light-Enhanced Blue Energy Generation Using MoS2 Nanopores

Michael Graf, Martina Lihter, Dmitrii Unuchek, Aditya Sarathy, Jean Pierre Leburton, Andras Kis, Aleksandra Radenovic

Research output: Contribution to journalArticle

Abstract

Blue energy relies on the chemical potential difference between solutions of high and low ionic concentrations, potentially providing an independent energy source at estuaries around the world. The energy conversion relies on reverse electrodialysis via ion-selective membranes. A novel generation of these membranes is based on nanopores in atomically thin material. Single nanopores in molybdenum disulfide (MoS2)-based membranes have shown record-high power outputs in alkaline conditions. By increasing the surface charge of MoS2 membranes by light, we can double the osmotic power generated by a single nanopore at a neutral pH. The increased surface charge at the pore rim enhances the ion selectivity and leads to a larger osmotic voltage (dominating in small pores), while the increased surface charge of the membrane enhances the surface conductance, leading to a larger osmotic current (dominating in larger pores). The combination of these effects could efficiently boost the energy generation using membranes containing arrays of nanopores of varying sizes. The chemical potential difference between seawater (high salinity) and river water (low salinity) holds vast amounts of energy. Blue energy attempts to harvest this currently untapped energy source at estuaries. The efficiency of the energy conversion via reverse electrodialysis is inversely proportional to the thickness of the ion-selective membrane. Monatomically thin membranes, such as molybdenum disulfide (MoS2) monolayer, provide the ultimate achievable efficiency. The osmotic power in these membranes can be additionally enhanced by increasing the surface charge of the material. However, methods for tuning the surface need to be environmentally compatible. Since MoS2 is an intrinsic semiconductor, it allows changes to its electronic structure by light irradiation. This affects the surface charge and increases the osmotic power during light illumination by 130%. In practice, directing sunlight onto the membranes during daytime can boost the osmotic power generation. A vast amount of energy is available at estuaries around the world where river water with low salinity meets high-salinity ocean water. Today, this energy is largely untapped because of the very low efficiency of current ion-exchange membranes. Here, we propose a membrane in monolayer MoS2 to overcome poor ion-transport rates of conventional membranes. By exploiting the photoexcitability of the semiconducting MoS2 membrane, we increase the surface charge and boost the energy production during daytime.

Original languageEnglish (US)
Pages (from-to)1549-1564
Number of pages16
JournalJoule
Volume3
Issue number6
DOIs
StatePublished - Jun 19 2019

Keywords

  • 2D membrane
  • MoS
  • blue energy
  • energy
  • ion selective
  • laser
  • light
  • membrane
  • molybdenum disulfide
  • nanopore
  • osmosis
  • power
  • reverse electrodialysis
  • surface charge

ASJC Scopus subject areas

  • Energy(all)

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  • Cite this

    Graf, M., Lihter, M., Unuchek, D., Sarathy, A., Leburton, J. P., Kis, A., & Radenovic, A. (2019). Light-Enhanced Blue Energy Generation Using MoS2 Nanopores. Joule, 3(6), 1549-1564. https://doi.org/10.1016/j.joule.2019.04.011