Abstract
The salinity gradient between seawater and river water is a clean energy source and an alternative solution for the increasing energy demands. A membrane-based reverse electrodialysis technique is a promising strategy to convert osmotic energy to electricity. To overcome the limits of traditional membranes with low efficiency and high resistance, nanofluidic is an emerging technique to promote osmotic energy harvesting. Here, we engineer a high-performance nanofluidic device with a hybrid membrane composed of a silk nanofibril membrane and an anodic aluminum oxide membrane. The silk nanofibril membrane, as a screening layer with condensed negative surface and nanochannels, dominates the ion transport; the anodic aluminum oxide membrane, as a supporting substrate, offers tunable channels and amphoteric groups. Thus, a nanofluidic membrane with asymmetric geometry and charge polarity is established, showing low resistance, high-performance energy conversion, and long-term stability. The system paves avenues for sustainable power generation, water purification, and desalination.
Highlights
The salinity gradient between seawater and river water is a clean energy source and an alternative solution for the increasing energy demands
To obtain the silk nanofibrils, the sericin proteins must be removed to deconstruct the hierarchical structure of silk fibers by using various solvent treatment[27]
For the fabricated hybrid membrane, the cross-section Scanning electron microscopy (SEM) images revealed a 5-μm-thick Silk nanofibril (SNF) layer attaching onto a 60-μm-thick anodic aluminum oxide (AAO) substrate (Fig. 1e) whose structure was further examined (Supplementary Fig. 3a and b)
Summary
The salinity gradient between seawater and river water is a clean energy source and an alternative solution for the increasing energy demands. Siria et al and Feng et al successfully developed unique boron nitride nanotube and singlelayer MoS2 nanopores for osmotic energy harvesting and demonstrated the output power density of up to several 103 W m−2 and 106 W m−2, respectively[18,19] These fundamental studies greatly stimulate the development of intelligent nanoporous membrane systems for various practical applications[20]. To improve the energy density, our group has reported a series of composite systems based on track-etched membranes and self-assembly block copolymer (BCP) membranes, which achieved substantial increases in the output power density, up to 0.35 W m−2 and 2.04 W m−2, respectively[14,22] These materials still suffer from high-cost, complex preparation, low output power density, and poor long-term stability, which constrain their practical applications[14].
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