Abstract
High ion selectivity and high structural stability have always been the pursuit of nanofluidic ion exchange membranes but they are often trade-offs. Herein, we built a sandwich structure by introducing parallel arrays of clay nanosheets in two-dimensional nanofluidic membrane to improve the ion transport performance. The introduction of an appropriate amount of clay nanosheets can not only redistributes internal stress and thereby increases the tensile strength but also provides higher surface charge density and thereby effectively increases ion selectivity of the membrane. The current density obtained from the sandwich structure membrane is ∼5 times than that of the homogeneous membrane and the cation mobility can reach a maximum of 0.98. When simulating the energy conversion of seawater and river water, the maximum output power density achieved through the membrane is 0.70 W m−2, which is increased by ∼6 times. Interestingly, it significantly weakens the internal resistance from 100 to 30 kΩ and the energy barriers from 4.56 to 2.13 kJ mol−1 of ion permeation in the entire regime although the clay nanosheets arrays increases the thickness of the membrane. This strategy of introducing negatively charged nanosheets of natural minerals to enhance ion transport properties provides a new idea for the enhancement and application of salinity gradient energy harvesting membranes.
Published Version
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