Research ArticleAPPLIED SCIENCES AND ENGINEERING

Unique ion rectification in hypersaline environment: A high-performance and sustainable power generator system

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Science Advances  26 Oct 2018:
Vol. 4, no. 10, eaau1665
DOI: 10.1126/sciadv.aau1665
  • Fig. 1 Schematic depiction of the Janus 3D porous membrane–based osmotic power generator.

    (A) Preparation process of the Janus nanoporous membrane. (B and D) Chemical structure (top), microstructure of ionomers (middle), and statistics of pore size and Gauss fitting profile (bottom). The ionomers are PES-Py and PAEK-HS. (C) Schematic (left) and scanning electron microscopy observation (right) of the cross section of the asymmetric structure with 3D pores. The thickness of the PES-Py layer is about 1 μm. (E) Schematic depiction of the harvesting osmotic energy process under a concentration gradient based on the Janus 3D porous membrane.

  • Fig. 2 Microscopic appearance characterization of PAEK-HS with tuned pendant proportion.

    (A to C) TEM images of HS10, HS15, and HS20. The copolymers were marked with AgNO3, which reacted with the sulfonic acid moiety. Dark areas refer to pores formed by the hydrophilic pendants, and light areas represent the hydrophobic backbone. (D) Porosity and diameters of the copolymer membranes. While the pore size is well-defined uniform, the porosity of the polymer membrane is enlarged with the increasing pendant proportion. The statistics were obtained from the TEM images.

  • Fig. 3 The ionic transmembrane property of the Janus membrane.

    (A) Conductance versus salt concentration for various Janus membranes with HS10, HS15, and HS20 at pH 5. (B) Representative rectification I-V curve in 3 M KCl. The anode is on the PES-Py side, and the cathode is on the HS20 side. (C) Rectification ratio of the HS20 Janus membrane under a series of KCl solution concentration with pH 5. (D) Numerical simulation results of the ionic concentration distribution along the X axial position at −2 V and +2 V of the theoretical 1D model. The X = 0 nm position refers to the PAEK-HS side. The inset shows the calculated ion concentration profile. (E) I-V curves of the Janus membrane under two different configurations for the placement of electrolyte solutions. With the high concentration of KCl solution on the PES-Py side, the absolute value of Ishort increases by approximately 40%. The high and low concentrations of KCl solutions are 1 M and 10 μM, respectively. (F) Numerical simulation results of the ionic concentration distribution along the Y axial position at the end of the low concentration solution. The preferential directions are the high concentration of the solution on the PES-Py side and the low concentration of the solution on the PAEK-HS side. The Y = 0 nm position refers to the surface of the channels along the radial direction.

  • Fig. 4 Ultrahigh output power density of the Janus 3D porous membrane–based osmotic power generator.

    The collected power is transferred to the external circuit to supply an electronic load (inset). (A and B) Current density and output power of PES-Py/HS10, PES-Py/HS15, and PES-Py/HS20 as functions of load resistance. The PES-Py side was placed to artificial seawater (0.5 M NaCl), while the PAEK-HS side was placed to artificial river water (0.01 M NaCl). With increasing load resistance, the current density is reduced and the output power reaches a maximum at a moderate resistance. (C) The maximum output power density goes up with the increasing pendant proportion. The maximum PES-Py/HS20 is about 2.6 W/m2. (D and E) Current density and output power of HS20 as functions of load resistance under three salinity gradients. The low-salinity solution was placed in the PAEK side and fixed at 0.01 M. High-salinity solution is tunable from 0.05 to 5 M NaCl. (F) With increased salinity gradients, the output power density goes up and reaches a maximum at a 500-fold salinity gradient. The maximum value is 5.10 W/m2.

  • Fig. 5 The robustness and high endurance of a high-performance generator based on the Janus membrane.

    (A) TGA curves of Janus membranes. The onset weight loss temperatures were higher than 200°C. (B) Swelling ratio of membranes at 20° and 80°C. The swelling is more pronounced by increasing the proportion of hydrophilic pendant. (C) Tensile strength of dry and wet membranes. (D) Elongation at break of dry and wet membranes. With increasing pendent proportion, the tensile strength is reduced, while the membrane displays a higher elongation at break. (E) A 0.02 mm–by–5 mm membrane can hang about 300 g of weight. (F) Time series of the current of the Janus membrane–based energy devices by mixing artificial river water and artificial seawater. (G) Tandem Janus membrane–based power generator can directly power a calculator.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/10/eaau1665/DC1

    Section S1. The optical photograph of the Janus nanoporous membrane

    Section S2. Materials

    Section S3. Measurements

    Section S4. Synthesis of PAEK-HS

    Section S5. Synthesis of PES-Py

    Section S6. Characterization of PAEK-HS

    Section S7. Characterization of PES-Py

    Section S8. Inherent viscosity of the copolymers

    Section S9. FT-IR spectra of PAEK-HS

    Section S10. Porosity and pore size distribution

    Section S11. Zeta potential of PAEK-HS

    Section S12. Ion exchange capacity

    Section S13. Model building

    Section S14. Experimental setup

    Section S15. The effect of the concentration gradients on short-circuit current and open-circuit voltage

    Section S16. Ion selectivity of the membrane

    Section S17. Energy conversion efficiency

    Section S18. Fabrication of Janus heterogeneous membrane

    Section S19. The performance of the membrane under neutral

    Section S20. Tandem membrane-based power electronic devices

    Section S21. Electrode calibration

    Fig. S1. Digital photo of the large-scale Janus nanoporous membrane with an approximate thickness of 11 μm.

    Fig. S2. 1H NMR spectra (500 MHz, CDCl3, room temperature) of monomer.

    Fig. S3. 1H NMR spectra (500 MHz, DMSO-d6, room temperature) of PAEK-HS15.

    Fig. S4. 1H NMR spectra (500 MHz, DMSO-d6, room temperature) of monomer.

    Fig. S5. 1H NMR spectra (500 MHz, DMSO-d6, room temperature) of PES-Py.

    Fig. S6. FT-IR spectra of PAEK-HP and PAEK-HS with different proportions of hydrophilic high concentration of sulfonated side chain (from top to bottom: 10, 15, and 20%, respectively).

    Fig. S7. The histogram of pore size distribution with Gaussian fit.

    Fig. S8. The zeta potential of membranes PAEK-HS10, PAEK-HS15, and PAEK-HS20.

    Fig. S9. The ion exchange capacity values of the sulfonated membranes.

    Fig. S10. Numerical simulation model based on PNP theory.

    Fig. S11. Numerical simulation results of the effect of the surface charge density on the ICR ratio.

    Fig. S12. Schematic of the electrochemical testing setup.

    Fig. S13. Vopen and Ishort of HS10, HS15, and HS20 under various concentration gradients (KCl).

    Fig. S14. Visual experiment for the selectivity.

    Fig. S15. The output power and current density of PES-Py/HS20 under a series of external load resistance at pH 7.4.

    Fig. S16. I-V curves of the 10 units’ device under river water (0.01 M NaCl) on the HS side and seawater (0.5 M NaCl) on the Py side.

    Fig. S17. The equivalent circuit diagram of the testing system.

    Scheme S1. Synthesis of PAEK-HS.

    Scheme S2. Synthesis of PES-Py.

    Table S1. Inherent viscosity of the copolymers.

    Table S2. The conversion efficiency of the Janus membrane at different salinity gradients.

    Table S3. V, ERedox, and EDiff of HS10, HS15, and HS20.

    References (39, 40)

  • Supplementary Materials

    This PDF file includes:

    • Section S1. The optical photograph of the Janus nanoporous membrane
    • Section S2. Materials
    • Section S3. Measurements
    • Section S4. Synthesis of PAEK-HS
    • Section S5. Synthesis of PES-Py
    • Section S6. Characterization of PAEK-HS
    • Section S7. Characterization of PES-Py
    • Section S8. Inherent viscosity of the copolymers
    • Section S9. FT-IR spectra of PAEK-HS
    • Section S10. Porosity and pore size distribution
    • Section S11. Zeta potential of PAEK-HS
    • Section S12. Ion exchange capacity
    • Section S13. Model building
    • Section S14. Experimental setup
    • Section S15. The effect of the concentration gradients on short-circuit current and open-circuit voltage
    • Section S16. Ion selectivity of the membrane
    • Section S17. Energy conversion efficiency
    • Section S18. Fabrication of Janus heterogeneous membrane
    • Section S19. The performance of the membrane under neutral
    • Section S20. Tandem membrane-based power electronic devices
    • Section S21. Electrode calibration
    • Fig. S1. Digital photo of the large-scale Janus nanoporous membrane with an approximate thickness of 11 μm.
    • Fig. S2. 1H NMR spectra (500 MHz, CDCl3, room temperature) of monomer.
    • Fig. S3. 1H NMR spectra (500 MHz, DMSO-d6, room temperature) of PAEK-HS15.
    • Fig. S4. 1H NMR spectra (500 MHz, DMSO-d6, room temperature) of monomer.
    • Fig. S5. 1H NMR spectra (500 MHz, DMSO-d6, room temperature) of PES-Py.
    • Fig. S6. FT-IR spectra of PAEK-HP and PAEK-HS with different proportions of hydrophilic high concentration of sulfonated side chain (from top to bottom: 10, 15, and 20%, respectively).
    • Fig. S7. The histogram of pore size distribution with Gaussian fit.
    • Fig. S8. The zeta potential of membranes PAEK-HS10, PAEK-HS15, and PAEK-HS20.
    • Fig. S9. The ion exchange capacity values of the sulfonated membranes.
    • Fig. S10. Numerical simulation model based on PNP theory.
    • Fig. S11. Numerical simulation results of the effect of the surface charge density on the ICR ratio.
    • Fig. S12. Schematic of the electrochemical testing setup.
    • Fig. S13. Vopen and Ishort of HS10, HS15, and HS20 under various concentration gradients (KCl).
    • Fig. S14. Visual experiment for the selectivity.
    • Fig. S15. The output power and current density of PES-Py/HS20 under a series of external load resistance at pH 7.4.
    • Fig. S16. I-V curves of the 10 units’ device under river water (0.01 M NaCl) on the HS side and seawater (0.5 M NaCl) on the Py side.
    • Fig. S17. The equivalent circuit diagram of the testing system.
    • Scheme S1. Synthesis of PAEK-HS.
    • Scheme S2. Synthesis of PES-Py.
    • Table S1. Inherent viscosity of the copolymers.
    • Table S2. The conversion efficiency of the Janus membrane at different salinity gradients.
    • Table S3. V, ERedox, and EDiff of HS10, HS15, and HS20.
    • References (39, 40)

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