Nanofluidic Membranes to Address the Challenges of Salinity Gradient Energy Harvesting: Roles of Nanochannel Geometry and Bipolar Soft Layer

Abstract

Researchers are looking for new, clean, and accessible sources of energy due to rising global warming caused by the usage of fossil fuels and the irreversible harm that this does to the environment. Water salinity is one of the newest and most accessible renewable energy sources, which has sparked a lot of interest. Reverse electrodialysis (RED) has been utilized in the past to turn saline water into electricity. NRED, a reverse electrodialysis method utilizing nanofluidics, has gained popularity as nanoscale research advances. Developing and evaluating NRED systems is time-consuming and expensive due to the method’s novelty; thus, modeling is required to identify the best locations for implementation and to comprehend its workings. In this work, we examined the influence of bipolar soft layer and nanochannel geometry on ion transfer and power production simultaneously. To achieve this, the two trumpet and cigarette geometries were coated with a bipolar soft layer so that both negative (type (I)) and positive (type (II)) charges could be positioned in the nanochannel’s small aperture. After that, at steady state conditions, the Poisson–Nernst–Planck (PNP) and Navier–Stokes (NS) equations were solved concurrently. The findings revealed that altering the nanochannel coating from type (I) to type (II) alters the channel’s selectivity from cations to anions. An approximately 22-fold improvement in energy conversion efficiency was achieved by raising the concentration ratio from 10 to 100 for the type (I) trumpet nanochannel. Type (I) cigarette geometry is advised for maximum power output at low and medium concentration ratios, whereas type (I) trumpet geometry is recommended for the maximum power production at high concentration ratios.

Salinity Gradient-Induced Power Generation in Nanochannels: The Role of pH-Sensitive Polyelectrolyte Layers

“…For the PEL domain normal∇ · ( ε P E L ∇ ψ ) = prefix− F ∑ i = 1 4 z i c i − σ normalP normalE normalL Here, σ PEL is the PEL space charge density and c i and z i are concentration and valance of the i th ionic species, respectively. Moreover, the value of electrical permittivity ratio is taken as ε PEL /ε v = 0.2 and ε v = 80ε 0 …”

Combined electroosmotic and pressure‐driven transport of neutral solutes across a rough, porous‐walled microtube

“…It is found that each of these shapes leads to the optimization of one of the key indicators. Another major research interest in this area is assessing the effect of soft micro/nanoconduits, and how such systems can play a key role in salinity energy generation (SEG) and energy harvesting [11][12][13]. The system considered was a polyelectrolyte layer (PEL) grafted nanofluidic confinement, and it was revealed that augmentation in the temperature and concentration ratios leads to increase in the SEG.…”

Enhanced Ionic Current Rectification through Innovative Integration of Polyelectrolyte Bilayers and Charged-Wall Smart Nanochannels

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