Nanofiber-reinforced clay-based 2D nanofluidics for highly efficient osmotic energy harvesting

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2D nanofluidic membranes are capable of regulating ion transport toward various applications concerning energy and environment, which is primarily contributed by the excess charge on the interior surface of narrow nanoscale pores. However, there is still a lack of comprehensive summaries and discussions on the surface charge modification principles and strategies of 2D nanofluidic membranes, as well as the practical applications of charge‐modified 2D nanofluidic membranes for regulating ion transport. In this review, the surface charge modification principles and charge modification methods of 2D nanofluidic membranes are first introduced in detail, which is of great significance for improving the ion regulation capability of membranes and realizing the design of nanochannel materials. Next, recent advances in the two typical applications of concentration cells and water treatment based on charge‐modified 2D nanofluidic membranes are summarized. Finally, some challenges and prospects related to charge‐modified 2D nanofluidic membranes are discussed to indicate directions for future research in this field. It is anticipated that this review will provide valuable strategies for the development of high‐performance charge‐modified 2D nanofluidic membranes toward energy and environment applications.

Section: Materials Compositingmentioning

confidence: 99%

Section: Concentration Cellsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Surface Charge Modification on 2D Nanofluidic Membrane for Regulating Ion Transport

Xie

Tang

Qin

et al. 2022

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Zwitterionic Gradient Double‐Network Hydrogel Membranes with Superior Biofouling Resistance for Sustainable Osmotic Energy Harvesting

Huang

Hung

et al. 2023

Developing ion‐selective membranes with anti‐biofouling property and biocompatibility is highly crucial in harvesting osmotic energy in natural environments and for future biomimetic applications. However, the exploration of membranes with these properties in osmotic energy conversion remain largely unaddressed. Herein, a tough zwitterionic gradient double‐network hydrogel membrane (ZGDHM) with excellent biofouling resistance and cytocompatibility for sustainable osmotic energy harvesting is demonstrated. The ZGDHM, composed of negatively charged 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) as the first scaffold network and zwitterionic sulfobetaine acrylamide (SBAA) as the second network, is prepared by a two‐step photopolymerization, thus creating continuous gradient double‐network nanoarchitecture and then remarkably enhanced mechanical properties. As verified by the experiments and simulations, the gradient nanoarchitecture endows the hydrogel membrane with apparent ionic diode effect and space‐charge‐governed transport property, thus facilitating directional ion transport. Consequently, the ZGDHM can achieve a power density of 5.44 W m−2 by mixing artificial seawater and river water, surpassing the commercial benchmark. Most importantly, the output power can be promoted to an unprecedented value of 49.6 W m−2 at the mixing of salt‐lake water and river water, nearly doubling up most of the existing nanofluidic membranes. This study paves a new avenue toward developing ultrahigh‐performance osmotic energy harvesters for biomimetic applications.

In Situ Growth of Imine‐Bridged Anion‐Selective COF/AAO Membrane for Ion Current Rectification and Nanofluidic Osmotic Energy Conversion

Chen,

Yang,

Wang

et al. 2023

Facing the energy crisis, using the salinity gradient between seawater and freshwater for osmotic energy conversion is a direct way to obtain energy. So far, most nanofluidic membranes utilized for osmotic energy generation are cation‐selective. Given that both anion‐ and cation‐selective membranes have the identical importance for energy conversion devices, it is of great significance to develop anion‐selective membranes. Herein, an anion‐selective membrane is synthesized by in situ growth of imine‐bridged covalent organic framework (COF) on ordered anodic aluminum oxide (AAO) at room temperature. The imine groups and residual amino groups of COF can combine with protons in neutral solution, enabling the COF positively charged and efficiently transport of anions. Particularly, due to the asymmetry in the charge and structure of COF/AAO, the as‐prepared membrane exhibits excellent ionic current rectification property, which can inhibit ion concentration polarization effectively and possess high ion selectivity and permeability. Using the present COF/AAO membrane, salinity gradient energy can be successfully harvested from solutions with high salt content, and the output power density reached 17.95W m−2 under a 500‐fold salinity gradient. The study provides a new avenue for construction and application of anion‐selective membranes in the smart ion transport and efficient energy conversion.