Clay-Based Nanofluidic Membrane Derived from Vermiculite Nanoflakes for Pressure-Responsive Power Generation

Abstract

The intrinsic thermal and chemical stability of vermiculite clay is exploited here to fabricate a robust and responsive energy device that consumes atmospheric water molecules as the cathode reagent. A nanofluidic membrane of clay was prepared by reconstructing exfoliated nanolayers of natural vermiculite clay and doped with poly­(diallyldimethylammonium chloride) (PDDA). X-ray diffraction studies determined the height of the two-dimensional nanofluidic channels to be ∼0.41 nm. Application of a modest pressure of 56 kPa, on the Al foil placed on top of a PDDA-doped nanofluidic vermiculite membrane (PDDA-VM), yields a stable potential of ∼0.8 V. The output current value of the clay-based devices can be tuned by varying parameters like intercalating cations, device geometry, thickness of the polymeric coating, and applied pressure. The natural clay-based energy device is found to be highly robust; exposure to liquid nitrogen (−195 °C), heat pulse (450 °C), water steams, and mechanical stress (100 N) did not deteriorate its performance. Interestingly, the PDDA-VMs exhibit extraordinary fire retardancy, with ∼70% recovery in the power output after exposure to an open flame.

Applications of Lamellar Membranes Reconstructed from Clay Mineral-Based Nanosheets: A Review

“…Such flame retardant devices could open up novel opportunities for designing futuristic inflammable energy devices. 48 3.9. Special Wettability.…”

“…Researchers across the world already started exploiting this property of clay layers to fabricate inflammable energy devices that can be operated under challenging environments such as elevated temperatures. 48 One of the least explored qualities of clay membranes is their low thermal and electrical conductivities. Clay minerals are among the best know thermal insulating materials (typical thermal conductivity value less than 1 W m −1 K −1 ).…”

“…In this method, a large amount of clay layers can be exfoliated in a very convenient and reliable manner. Representative AFM and TEM images of the 2D flakes prepared by this method are presented in Figure b and c, respectively. ,− Exfoliation through the ion exchange method is based on the remarkable observation made by Walker and Garrett as early as 1967 . The duo reported that with appropriate interlayer cations, clay minerals can imbibe a large amount of water molecules and swell in the direction perpendicular to the planes of 2D layers.…”

“…Typically, in the first step of exfoliation, the native ions were exchanged with Na + ions by refluxing the raw particles for 24 h in a saturated aqueous solution of NaCl. After washing with alcohol and water, the Na + ions were exchanged with another ion of bigger hydration radius (such as Li + or Ba 2+ ) by refluxing the samples with concentrated solutions of the respective electrolytes. ,− , The excess metal ions used during the exfoliation process can be removed from the exfoliated layers by repeated washing with deionized water and ethanol employing filtration or centrifugation methods. The interlayer cations are an integral part of the clay structure and a major contributor to the overall properties of clay-based materials.…”

Precise Cation Recognition in Two-Dimensional Nanofluidic Channels of Clay Membranes Imparted from Intrinsic Selectivity of Clays

“…32 Raidongia et al also fully applied the intrinsic thermal stability of vermiculite to fabricate a pressure-responsive energy device; the reconstructed clay nanofluidic membrane was highly robust and exhibited excellent fire retardancy with about 70% recovery in the power output after exposure to an open flame. 33 Hence, it can be deduced that the intrinsic thermal and chemical stability of clay membranes have already been demonstrated to play a crucial role in the fabrication of energy-harvesting and storage devices aimed at high-temperature applications.…”