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Ion-exchange membranes have been widely used to harvest osmotic energy in the past decades. However, conventional ion-exchange membranes suffer from low output power and poor conversion efficiency due to their limited pores and high membrane resistance. Herein, a sodium alginate (SA)/3-sulfopropyl acrylate potassium salt (SPAK) hydrogel membrane which has good cationic selectivity and can effectively harvest osmotic energy is designed, yielding a maximum power density of 16.44 W/m2 under a 50-fold NaCl concentration gradient and 36.85 W/m2 with ion selectivity of 0.73 at 500-fold. Furthermore, by introducing Zr4+, post-crosslinking reaction was employed to prepare tougher hydrogel membranes at room temperature for breaking a trade-off between selectivity and permeability, boosting a maximum power density up to 25.07 W/m2 under a 50-fold NaCl concentration gradient and 121.66 W/m2 with a high cation selectivity of 0.87 at 500-fold. Importantly, the resultant SA/SPAK/Zr4+ membrane reveals excellent osmotic energy harvesting property with the largest thickness of 500 μm, exceeding other reported porous nanofluidic membranes. Theoretical calculations correlate the enhanced power density of SA/SPAK/Zr4+ membranes with the enriched Cl- and smaller pore size after the introduction of Zr4+. This work paves an avenue to design and develop the 3D hydrogel membranes for high-performance osmotic energy generators. [Display omitted] • Zr4+ was introduced into a SA/SPAK hydrogel membrane to obtain a tougher SA/SPAK/Zr4+ hydrogel membrane. • The introduction of Zr4+ increased the power density of the hydrogel membrane from 36.85 to 121.66 W/m2 at 500-fold. • The designed hydrogel membranes have the largest thickness of porous nanofluidic membrane-based RED reported to date. • The designed three-dimensional SA/SPAK/Zr4+ hydrogel membranes break the trade-off between selectivity and permeability. • The enhanced osmotic energy conversion of SA/SPAK/Zr4+ hydrogel membrane was confirmed by simulations. [ABSTRACT FROM AUTHOR]

Abstract Nature is the source of human being's creativity and always inspires people to break through the existing bottleneck of science and technology. Electric eel (Electrophorus electricus) relying on ion channel in electrocyte can convert salinity gradient energy to electricity power with potentials of ~600 V to stun prey and ward off predators. Inspired by biological ion channels, artificial nanochannels have been extensively explored to mimic the control of ion flow in nanosize confinement space and apply in salinity gradient power generation. In this paper, polyether sulfone/sulfonated polyether sulfone (PES/SPES) membranes with large amount of nanochannels are constructed by using phase separation method to be applied in the salinity gradient power generation field. The content of SPES, the concentration of casting solution, and the thickness of prefabricated membrane were taken into account to control the structural and surface charge distribution of membrane. The prepared serials PES/SPES membrane with nanopore structure display much proper cation selectivity, excellent ion conductivity and output power density (reach up to 2.48 W/m2) for salinity gradient power generation. In addition, the proposed membrane with low cost and easy casting process shows great potential for the practical application in salinity gradient power generation. Graphical abstract Engineered PES/SPES membrane with nanochannel structure displays excellent ion conductivity property and output power density for salinity gradient power generation. fx1 Highlights • PES/SPES membrane with nanochannel and ultrathin functional layer is constructed by phase separation method. • The PES/SPES membrane shows excellent ion transport and high output power density for salinity gradient power generation. • The low cost and easy fabrication of the PES/SPES membrane make a potential for large-scale application. [ABSTRACT FROM AUTHOR]

In living organisms, many biological processes are inextricably linked with light, such as the photosynthesis systems and rhodopsin. Hence, construction of light-sensitive biomimetic-nanochannels, which can realize the functions of cells and other membrane structures with high degree of spatial and temporal control, is particularly attractive and challenging. As a cornerstone of light-sensitive nanochannels, the photoresponsive materials are a big family and at their mature stage after several decades of development, which can provide different strategies to construct biomimetic photoresponsive nanochannels. In this review, we mainly summarize the construction and applications of photoresponsive nanochannels on the basis of various photoresponsive materials. The construction of photoresponsive nanochannels can be classified into four categories: photoresponsive inorganic nanochannels based on inorganic-compound-based photonic sensitive materials; photoresponsive organic nanochannels based on organic-compound-based photonic sensitive materials; photoresponsive polymers nanochannel based on photoresponsive polymers materials and potential photoresponsive nanochannels based on other photoresponsive materials. After introducing the construction of photoresponsive nanochannels, the review highlights some of the most recent applications of photoresponsive nanochannels in separation, energy conversion and storage, drug delivery and so on. [ABSTRACT FROM AUTHOR]

The selectivity filter of biological ion channels could well split ion's hydration shell at the entryway of channels with subtle opening sizes, leading to the 'naked' ion's rapid transport across the channels. Numerous artificial nanochannels have been developed for mimicking this. However, the precise fabrication of nanochannels/nanopores with targeted diameters has been always a challenge. Herein, we employ the immiscible liquid-infused channels to regulate the ion's hydration shell and mimic the ion transport processes. Experimental and theoretical results show the partial removal of water molecules around ions at the entrance of the nanochannels and low-resistance migration of ions in the immiscible liquid phase. Compared with the pristine membrane, the cross-membrane conductance and osmotic energy power density of the proposed membrane have increased by ∼4-fold and ∼77.3%, respectively. Moreover, this approach avoids the far-reached technique and could be easily adapted to various membrane materials. Therefore, this strategy holds great potential in systems requiring ion transport across membranes, including ion separation, battery, and desalination, etc. [Display omitted] • Bio-inspired immiscible liquid-mediated nanochannel endow the dehydrated ion with ultrafast ion transport in the nanochannel. • Immiscible liquid-mediated nanochannels benefit boosting the osmotic energy conversion performance of membranes. • Immiscible liquid-mediated nanochannels can enhance biofouling-resistant ability of membranes. [ABSTRACT FROM AUTHOR]

This paper considers the problem of robust stability for a class of linear systems with interval time-varying delay and nonlinear perturbations. Less conservative stability criteria was put forward by using delay-partitioning approach. By decomposing the delay interval into multiple equidistant subintervals, new Lyapunov–Krasovskii (L–K) functional contains some triple-integral terms and augment terms which are introduced on these intervals, thus resulting in being much less conservative than most existing results in the literature. In addition, in deriving the stability conditions in linear matrix inequality (LMI) framework, neither model transformations nor superfluous free-weighting matrix are employed for dealing the cross-terms that emerge from the time derivative of the L–K functional; instead, they are dealt using tighter integral inequalities which only contain a minimal number of slack matrix variables. Numerical examples are given to demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The development and utilization of salinity gradient energy are of great significance to the carbon-neutral strategic demand for clean energy in the new era. Conventional ion-exchange membranes have been employed to recover this wide-distributed energy by reverse electrodialysis membrane processes, however, the dense membrane structure and chemical instability limit the ionic transport in various working environments. Here, inspired by the rapid mass transport caused by the hierarchical structure of blood vessels, we employ two types of polyelectrolytes to fabricate a bioinspired three-dimensional interconnect porous membrane by simply casting-soaking, and this membrane shows great chemical stability due to the ionic crossing enhancement. The interconnected nanoporous structure and the enriched surface functional groups of the membrane render the high-performance osmotic energy conversion from different resources, including the Gibbs free energy between seawater and riverwater, commonly used organic solvents, and also in the solution treatment process of spent batteries. We believe this chemical-stable, nanoporous and freestanding membrane might take one more step towards practical applications and membrane technology. An poly (ionic liquid) membrane bioinspired by capillary vessel which can carry out rapid mass transfer is employed for efficient salinity gradient energy harvesting in both aqueous phase oil phase [Display omitted] • Bioinspired hierarchical nanoporous membrane is employed for nanofluidics ionic transport and osmotic energy conversion. • Polymeric nanoporous network induced by electrostatic crosslinking could work stably in various common organic solution. • Salinity gradient energy can be extracted by mimicking the solvent treatment process in the recycling of spent batteries. [ABSTRACT FROM AUTHOR]

Diverse nanoconfined ion transport behaviors have attracted increasing attention in constructing ion-channel-inspired nanoconfined systems for high nanofluidic energy conversion performance. Conventional nanofluidic systems cannot simultaneously obtain high ion-selectivity and high ion-flux in a large region due to the decreasing effect of the electrical double layer (EDL) formed on the charged surface. Here, space charge is introduced in the nanoconfined system to effectively solve this problem by employing the synergistic effect of surface and space charges. The charge effect contribution on controlled-ion-transport is further decoupled into surface charge, space charge and synergistic effects for the first time. The surface charge induces charge separation within the EDL in a smaller diameter channel while the space charge dominates the ion-selectivity by the ion-exchange mechanism in a larger diameter channel. The synergistic effect, contributed by EDL and ion-exchange effects, is extremely important in large (around 100 nm), short nanochannel (around 100 nm), and high concentration fold (around 1000-fold) conditions to achieve high ion-selectivity, ion-flux, and nanofluidic energy conversion performances, which is systematically analyzed by theoretical simulation results. These results reveal the mechanism for enhanced ion transport behaviors and provide a solid foundation for designing high-performance nanofluidic devices in fields of desalination, sensor, energy conversion and storage. Surface charge induces ions separation within electrical double layers in smaller diameter nanochannels while space charge dominates the ion-selectivity by the ion-exchange mechanism in larger diameter nanochannels. The synergistic effect, contributed by electrical double layer and ion-exchange effects, is extremely important in a large, short nanochannel, and high concentration conditions to achieve high ion-selectivity, ion-flux, and nanofluidic energy conversion performances. [Display omitted] • Highlight nanofluidic ion behaviors (selectivity and flux) can be improved by synergistic effect of surface and space charges. • Reveal that surface charge induces ion selectivity within EDL while space charge dominates that by ion-exchange mechanism. • Propose a method to quantitatively decouple and analyze the synergistic effect on nanofluidic energy conversion performances. [ABSTRACT FROM AUTHOR]

Bioinspired nanofluidic devices have drawn increasing global interest due to their giant applicable potential in a wide range of fields. By mimicking biological prototype, it is expected to achieve high energy conversion efficiency and tunable ion transport. However, the low osmotic conversion efficiency, weak ion transport capability and poor mechanical performance limit practical application. We designed a class of heterogeneous membrane consisting of a support layer and a thin top layer to meet fundamental requirements. To achieve higher power generation, we incorporated metal organic framework (MOF) nanosheets (dispersed phase) into polymer matrix (continuous phase) to afford a mixed matrix top layer. This unique structure addressed the geometric restriction associated with the polymeric specie due to their limited pore accessibility. As a result, the presented membranes produced high power density of ca. 7 W m−2 and a high energy conversion efficiency of ca. 40% under a salinity gradient of 50 (0.5 M|0.01 M, NaCl). This work thus offers an insight into a new methodology in the development of a novel membrane technology for highly efficient energy conversion. MOF enhanced SPEEK/SPSF heterogeneous membrane showed record-high salinity gradient energy conversion performance. ga1 • A SPEEK-MOF/SPSF heterogeneous membrane was fabricated, which has a record-high SGE conversion performance and promising application potential. • Some beneficial designs are synergistically integrated into composite, such as heterogenous structure, mixed matrix and temperature gradient. • The intrinsic pores of 2D ZnTCPP nanosheets shorten the ion transport path while maintaining selectivity. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting into hydrogen and oxygen in neutral electrolytes has great significance for future energy supply security, potentially offering a pathway for H 2 generation from seawater. However, the electrocatalytic hydrogen evolution reaction (HER) generally occurs at low rates in neutral solutions due to the low proton concentration in such media. Herein, we fabricated a novel HER catalyst capable of efficient H 2 evolution in water at neutral pH, comprising a nickel-molybdenum nitride nanowire array modified with metallic Ni nanoparticles (Ni/NiMoN). The entire Ni/NiMoN array was supported on a Cu foam. The Ni nanoparticles promoted the dissociation of adsorbed water to enhance the supply of protons in the neutral electrolyte, whilst the nanowire array imparted the electrode surface with underwater superaerophobic properties, thus allowing H 2 gas bubbles to detach from the electrode in a facile manner. On the basis of the synergies realized between the different electrode components, the Ni/NiMoN nanowire array electrode offered exceptional HER performance, with an overpotential of only 37 mV at a current density of 10 mA cm−2 in a neutral electrolyte. Results guide the development of next-generation earth-abundant element electrocatalysts for HER in neutral media. • A Ni-Mo nitride nanowire array modified with Ni nanoparticles was fabricated as H 2 evolution reaction (HER) catalyst. • The introduction of a water dissociation catalyst (Ni nanoparticles in this case) can boost the neutral HER performance. • The nanowire array with underwater superaerophobic property allowed H 2 gas bubbles to detach from the electrode facilely. • The nanowire array electrocatalyst exhibited outstanding HER performance in a neutral electrolyte. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks with programmed surface charge enable tunable permeation behaviors of water permeation of 15.5 to 34.5 L m−2 h−1 bar−1 and dye removal up to 99%. This is attributed to the modulation of wetting and solid surface energy which provide further insight into controllable molecular transport and design of nanomaterials for sieving, water treatment, and energy conversion. [Display omitted] Molecular separation is critical to mitigating the issues of water contamination and shortage and currently focuses on the use of framework materials fabricated by special building blocks. However, developing a simple and tunable synthesis methodology for materials with alternative permeation and selectivity remains challenging. Here, we fabricate a series of nanochannel membranes composed of uniform spherical covalent organic frameworks (COFs). Diversified spherical COFs have diameters ranging from ∼150 to ∼800 nm, therefore demonstrating a programmable surface charge distribution from −24 to −63 mV. COF membranes with tailor-made surface charge enable different surface energy levels and allow increasing water permeation of 15.5 to 34.5 L m−2 h−1 bar−1. Furthermore, COFs can also act as filters, achieving up to 99.7% rejection and separation of the opposite charged dyes. We expect these COFs with tunable surface charge to be applicable to variety of fields, including sieving, batteries, and water treatments. [ABSTRACT FROM AUTHOR]