Nekoubin Nader, Sadeghi Arman, Chakraborty Suman
Department of Mechanical Engineering, Amirkabir University of Technology, Tehran 15875-4413, Iran.
Department of Mechanical Engineering, University of Kurdistan, Sanandaj 66177-15175, Iran.
Langmuir. 2024 May 14;40(19):10171-10183. doi: 10.1021/acs.langmuir.4c00477. Epub 2024 May 3.
The inherent limits of the current produced by imposing salinity gradients along a nanofluidic channel having "hard" boundary walls heavily constrain the resulting energy harvesting efficacy, acting as major hindrances against the practicability of harnessing high power density from the mixing of water having different salinities. In this work, the infusion of variable-thickness polyelectrolyte layer of a conical shape is projected to augment salinity gradient power generation in nanochannels. Such a progressive thickening of a charged interfacial layer on account of axially declining ion concentration facilitates the shedding of enhanced numbers of mobile ions, bearing a net charge of equal and opposite to the surface-bound ions, into the mainstream current flow. We show that the proposed design can convert energy at a higher efficiency as compared to both solid-state and available polyelectrolyte layer (PEL)-covered nanochannels. The same is true for the maximum power density at moderate and high concentration ratios including natural salt gradient conditions for which more than 50% increase is achievable. The maximum values achieved for efficiency and power density read 50.3% and 6.6 kW/m, respectively. Our results provide fundamental insights on strategizing variable-thickness polyelectrolyte layer grafting on the nanochannel interfaces, toward realizing high-performance osmotic power generators by altering the local ionic clouds alongside the grafted layers and enhancing the ionic mobility by inducing a driving potential gradient concomitantly. These findings open up a new strategy of efficient conversion of the power of the salinity difference of seawater and river water into electricity in a nanofluidic framework, surpassing the previously established limits of blue energy harvesting technologies.
沿着具有“硬”边界壁的纳米流体通道施加盐度梯度所产生的电流的固有局限性，严重限制了由此产生的能量收集效率，成为阻碍从不同盐度的水混合中获取高功率密度实用性的主要障碍。在这项工作中，预计注入锥形可变厚度的聚电解质层可增强纳米通道中的盐度梯度发电。由于轴向离子浓度下降，带电界面层的这种逐渐增厚促进了更多带移动离子的脱落，这些离子的净电荷与表面结合离子的电荷大小相等、电性相反，并进入主流电流。我们表明，与固态和现有的聚电解质层（PEL）覆盖的纳米通道相比，所提出的设计能够以更高的效率转换能量。在中等和高浓度比（包括天然盐度梯度条件）下，最大功率密度也是如此，在这些条件下可实现超过50%的增长。效率和功率密度的最大值分别为50.3%和6.6 kW/m。我们的结果为在纳米通道界面上设计可变厚度聚电解质层接枝提供了基本见解，旨在通过改变接枝层旁边的局部离子云并同时诱导驱动电位梯度来提高离子迁移率，从而实现高性能渗透发电机。这些发现开辟了一种在纳米流体框架内将海水和河水盐度差的能量高效转换为电能的新策略，超越了先前确立的蓝色能源收集技术的极限。
