Boosting Osmotic Energy Conversion of Graphene Oxide Membranes via Self-Exfoliation Behavior in Nano-Confinement Spaces.

Introducing alien intercalations to sub-nanometer scale nanochannels is one desirable strategy to optimize the ion transportation of two-dimensional nanomaterial membranes for improving osmotic energy harvest (OEH). Diverse intercalating agents have been previously utilized to realize this goal in OEH, but with modest performance, complex operations, and physicochemical uncertainty gain. Here, we employ the self-exfoliation behavior of oxidative fragments (OFs) from graphene oxide basal plane under an alkaline environment to encapsulate detached OFs in nanochannels for breaking a trade-off between permeability and selectivity, boosting power density from 1.8 to 4.9 W m-2 with a cation selectivity of 0.9 and revealing a negligible decline in power density and trade-off during a long-term operation test (∼168 h). The strategy of membrane design, employing the intrinsically self-exfoliated OFs to decorate the nanochannels, provides an alternative and facile approach for ion separation, OEH, and other nano-fluidic applications.

Enhanced Ion Sieving of Graphene Oxide Membranes via Surface Amine Functionalization.

Membranes based on two-dimensional (2D) nanomaterials have shown great potential to alleviate the worldwide freshwater crisis due to their outstanding performance of freshwater extraction from saline water via ion rejection. However, it is still very challenging to achieve high selectivity and high permeance of water desalination through precise d-spacing control of 2D nanomaterial membranes within subnanometer. Here, we developed functionalized graphene oxide membranes (FGOMs) with nitrogen groups such as amine groups and polarized nitrogen atoms to enhance metal ion sieving by one-step controlled plasma processing. The nitrogen functionalities can produce strong electrostatic interactions with metal ions and result in a mono/divalent cation selectivity of FGOMs up to 90 and 28.3 in single and binary solution, which is over 10-fold than that of graphene oxide membranes (GOMs). First-principles calculation confirms that the ionic selectivity of FGOMs is induced by the difference of binding energies between metal ions and polarized nitrogen atoms. Besides, the ultrathin FGOMs with a thickness of 50 nm can possess a high water flux of up to 120 mol m-2 h-1 without sacrificing rejection rates of nearly 99.0% on NaCl solution, showing an ultrahigh water/salt selectivity of around 4.31 × 103. Such facile and efficient plasma processing not only endows the GOMs with a promising future sustainable water purification, including ion separation and water desalination, but also provides a new strategy to functionalize 2D nanomaterial membranes for specific purposes.

The Influence of Separate and Combined Exercise and Foreign Language Acquisition on Learning and Cognition.

Aging contributes significantly to cognitive decline. Aerobic exercise (AE) has been shown to induce substantial neuroplasticity changes, enhancing cognitive and brain health. Likewise, recent research underscores the cognitive benefits of foreign language learning (FLL), indicating improvements in brain structure and function across age groups. However, the lack of a comprehensive paradigm integrating language learning with exercise limits research on combined effects in older adults. In order to address this gap, we devised a novel approach using a virtual world tourism scenario for auditory-based language learning combined with aerobic cycling. Our study examines the impact of simultaneous AE and FLL integration on cognitive and language learning outcomes compared to FLL alone. A total of 20 older adults were randomly assigned to AE + FLL and FLL-only groups. The results revealed significantly improved Spanish language learning outcomes in both combined and language learning-only groups. Additionally, significant cognitive function improvement was observed in the FLL group following short-term language learning.

Functionalized MoO3 Nanosheets for High-Efficiency RhB Removal.

2D nanostructured materials have been applied for water purification in the past decades due to their excellent separation and adsorption performance. However, the functional 2D nanostructured molybdenum trioxide (MoO3)has rarely been reported for the removal of dyes. Here, functionalized MoO3 (F-MoO3) nanosheets are successfully fabricated with a high specific surface area (106 cc g-1) by a one-step mechanochemical exfoliation method as a highly effective adsorbent for removing dyes from water. According to the Raman, X-ray photoelectron spectroscopy, Fourier transform infrared (FTIR), and selected area electron diffraction analysis, functional groups (hdroxyl groups, amide groups, amine groups and amino groups) are identified in the as-prepared F-MoO3 nanosheets. The attached functional groups not only facilitate the dispersal ability of F-MoO3 nanosheets but also enhance the adsorption capacities. Thus, the performance (up to 556 mg g-1 when the initial concentration of Rhodamine B solution is 100 mg L-1) of as-prepared F-MoO3 nanosheets is almost two times higher than other reported MoO3 materials. Furthermore, the FTIR spectra, isotherm, and several factors (e.g., adsorbent dosage and adsorbate dosage) are also systematically investigated to explore the adsorption mechanism. Therefore, this work demonstrates that the F-MoO3 nanosheets are a promising candidate for wastewater treatment.

Two-Dimensional Membranes with Highly Charged Nanochannels for Osmotic Energy Conversion.

Inadequate mass transportation of semipermeable membranes causes poor osmotic energy conversion from salinity-gradient. Here, the lamellar graphene oxide membranes (GOMs) constructed with numerous fusiform-like nanochannels, that are pre-filled with negatively charged polyanion electrolytes, to both enhance the ion permeability and ion selectivity of the membrane for energy harvest from the salinty gradient, were developed. The as-prepared membrane achieved the maximum output power density of ∼4.94 W m-2 under a 50 fold salinity gradient, which is 3.5 fold higher than that of pristine GOM. The enhancement could be ascribed to the synergistic impact of the expanded nanochannels and the enhanced space charge density. Via feeding with the artificial salinity water and monovalent cation electrolytes, the system could realise the power output up to 14.7 W m-2 and 34.1 W m-2 , respectively. Overall, this material design strategy could provide an alternative concept to effectively enhance ion transport of other two-dimensional (2D) membranes for specific purposes.

Eliminating Stubborn Insulated Deposition by Coordination Effect to Boost Zn Electrode Reversibility in Aqueous Electrolyte.

Aqueous rechargeable zinc-ion batteries (ZIBs) have recently shined in energy storage and transmission, which are due to high safety and low cost. However, the extremely stubborn by-products in the Zn anode severely inhibited the Zn2+ adsorption/desorption and exacerbated the dendrite formation. Herein, we report a facile strategy to eliminate inert Zn4(OH)6SO4·xH2O for the improvement of ZIBs according to the coordination effect by employing ethylenediaminetetraacetic acid-diamine (EDTA-2Na) as a coordination additive in traditional electrolyte. Zn2+ is coordinated with the carboxyl group of the four acetyl carboxyl groups and the N in C-N bonds, forming a new chelating structure, and thus stubborn deposition will be dissolved in the electrolyte. As a result, the discharge capacity of 102 mAh g-1 in the ZnSO4/Li2SO4 with EDTA-2Na electrolyte at a current density of 4 C and a stable cycle life with a capacity of 90.3% after 150 cycles are achieved. It has been concluded that the coordination effect strategy provides a valuable idea for solving the defects of ZIBs.

Molecular Simulations Guided Polymer Electrolyte towards Superior Low-Temperature Solid Lithium-Metal Batteries.

Low-temperature operation is a challenge for solid-lithium-metal batteries (LMBs), and insufficient ionic conductivity is the main obstacle. Herein, guided by the molecular dynamics simulations (MDS), a solid polymer electrolyte (SPE) based on poly(1,3-dioxolane) (PDOL) with sufficient ionic conductivity at low temperature is reported. In situ X-ray diffraction (XRD) and differential scanning calorimetry (DSC) tests reveal that the PDOL-based SPE could well maintain amorphous nature at low temperatures, contributing to excellent ionic transport. The MDS analysis of the Li-O coordination environment indicates that more oxygen atoms bonded with Li+ in PDOL than in poly(ethylene oxide) (PEO) at low temperatures, thus we could envision the preponderance of PDOL as a better polymer matrix of SPE for low-temperature solid LMBs. It delivers a high capacity of 103 mAh g-1 and 85% retention for 200 cycles for Li||LiFePO4 at -20 °C, showing great potential for application in low-temperature solid LMBs in cold climates.

Stable Ti3C2Tx MXene-Boron Nitride Membranes with Low Internal Resistance for Enhanced Salinity Gradient Energy Harvesting.

Extracting salinity gradient energy through a nanomembrane is an efficient way to obtain clean and renewable energy. However, the membranes with undesirable properties, such as low stability, high internal resistance, and low selectivity, would limit the output performance. Herein, we report two-dimensional (2D) laminar nanochannels in the hybrid Ti3C2Tx MXene/boron nitride (MXBN) membrane with excellent stability and reduced internal resistance for enhanced salinity gradient energy harvesting. The internal resistance of the MXBN membrane is significantly reduced after adding BN in a pristine MXene membrane, due to the small size and high surface charge density of BN nanosheets. The output power density of the MXBN membrane with 44 wt % BN nanosheets reaches 2.3 W/m2, almost twice that of a pristine MXene membrane. Besides, the output power density can be further increased to 6.2 W/m2 at 336 K and stabilizes for 10 h at 321 K, revealing excellent structure stability of the membrane in long-term aqueous conditions. This work presents a feasible method for improving the channel properties, which provides 2D layered composite membranes in ion transport, energy extraction, and other nanofluidic applications.

Transition Metal Dichalcogenide (TMD) Membranes with Ultrasmall Nanosheets for Ultrafast Molecule Separation.

Two-dimensional (2D) transition metal dichalcogenide membranes have entered the spotlight for nanofiltration application owing to the novel mass transport properties in nanochannels. However, further improving the water permeability with high molecular separation rate simultaneously is challenging. In this work, to achieve ultrafast molecule separation, MoS2 and WS2 nanosheets with ultrasmall lateral size (<100 nm) are fabricated by sucrose-assisted mechanochemical exfoliation. Ultrasmall nanosheets in the membranes cut down average length of water-transporting paths and create more nanochannels and nanocapillaries for water molecules to pass through membranes. The water flux of these kinds of MoS2 and WS2 membranes are significantly enhanced to 918 and 828 L/m2 h bar, respectively, which is four and two times higher than those of previously reported MoS2 and WS2 membranes with larger lateral size nanosheets. In addition, MoS2 and WS2 membranes display excellent rejection performance for rhodamine B and Evans blue with a high rejection rate (∼99%). This study provides a promising method to improve the performance of 2D laminar membranes for nanofiltration application by using ultrasmall 2D nanosheets.

Ultrafast, Stable Ionic and Molecular Sieving through Functionalized Boron Nitride Membranes.

Porous membranes play an important role in the separation technologies such as gas purification, solute nanofiltration, and desalination. An ideal membrane should be thin to maximize permeation speed, have optimum pore sizes to maximize selectivity, and be stable in various harsh conditions. Here, we show that the nanometer-thick membrane prepared by means of filtration of functionalized boron nitride (FBN) water suspensions can block solutes with hydrated radii larger than 4.3 Å in water. The FBN membranes with abundant nanochannels reduce the path length of ions. As molecular sieves, the FBN membrane can permeate small ions at an ultrahigh rate-a 25-fold enhancement compared with that of its theoretical diffusion rate and much higher than the graphene oxide membrane. Importantly, the FBN membrane exhibits excellent permeability even when it is immersed in acidic, alkaline, and basic salts solutions because of its intrinsic chemical stability. The molecular dynamics simulations further confirmed that the nanocapillaries formed within the FBN membrane in the hydrated state were responsible for high permeation performance. The simple vacuum filtration fabricated FBN membrane with angstrom-sized channels and ultrafast permeation of ions promises great potential applications in the areas of barrier separation and water purification.

Frontispiece: Improving the Performance of Microbial Fuel Cells through Anode Manipulation.

The frontispiece shows shows a microbial fuel cell capable of degrading organic matter and generating electron flux, therefore presenting potential applications in bioelectricity generation, bioremediation, bioproduction, and biosensing. The Minireview on page 1216 by X. Xie, W. Huang, and co-workers outlines progress in the anode manipulation of microbial fuel cells to improve biocompatibility, provide more space, and facilitate electron transfer. The resulting higher performance and lower cost would facilitate future applications and the commercialization of microbial fuel cells.

Improving the Performance of Microbial Fuel Cells through Anode Manipulation.

The continued focus on microbial fuel cells (MFCs) is due to their applications in power generation and simultaneous wastewater treatment. In the past decade, MFCs have been developed as a new class of energy devices and hold promise for broad applications in bioremediation, bioproduction, and biosensing. Despite the advances, the overall performance of MFCs is still limited, and particularly the energy loss at anode, where electrons are generated, is a restriction. Recent progress on MFC anodes has led to several effective approaches to improve MFC performance. In this Minireview, we discuss the performance losses in MFC anodes from the electrochemical point of view and then focus on the main strategies developed to overcome the anode performance losses. We also discuss the potential directions of future research on MFC anodes.