Self-assembled dendrimer polyamide nanofilms with enhanced effective pore area for ion separation.

Membrane technology using well-defined pore structure can achieve high ion purity and recovery. However, fine-tuning the inner pore structure of the separation nanofilm to be uniform and enhance the effective pore area is still challenging. Here, we report dendrimers with different peripheral groups that preferentially self-assemble in aqueous-phase amine solution to facilitate the formation of polyamide nanofilms with a well-defined effective pore range and uniform pore structure. The high permeabilities are maintained by forming asymmetric hollow nanostripe nanofilms, and their well-designed ion effective separation pore ranges show an enhancement, rationalized by molecular simulation. The self-assembled dendrimer polyamide membrane provides Cl-/SO42- selectivity more than 17 times that of its pristine polyamide counterparts, increasing from 167.9 to 2883.0. Furthermore, the designed membranes achieve higher Li purity and Li recovery compared to current state-of-the-art membranes. Such an approach provides a scalable strategy to fine-tune subnanometre structures in ion separation nanofilms.

Au3+ Species Boost the Catalytic Performance of Au/ZnO for the Semi-hydrogenation of Acetylene.

Au nanoparticles have garnered remarkable attention in the chemoselective hydrogenation due to their extraordinary selectivity. However, the activity is far from satisfactory. Knowledge of the structure-performance relationship is a key prerequisite for rational designing of highly efficient Au-based hydrogenation catalysts. Herein, diverse Au sites were created through engineering their interactions with supports, specifically via adjusting the support morphology, that is, flower-like ZnO (ZnO-F) and disc-like ZnO (ZnO-D), and the catalyst pretreatment atmosphere, that is, 10 vol % O2/Ar and 10 vol % H2/Ar (denoted as -O and -H, respectively). The four samples of Au/ZnO were characterized by various techniques and evaluated in the semi-hydrogenation of acetylene. The transmission electron microscopy results indicated that the Au particle sizes are almost similar for our Au/ZnO catalysts. The charge states of Au species demonstrated by X-ray photoelectron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy with CO as the probe molecule, and simulation based on density functional theory, however, are greatly dependent on the ZnO shape and pretreatment atmosphere, that is, the percentage of Au3+ reduces following the order of Au/ZnO-F-O > Au/ZnO-F-H > Au/ZnO-D-O > Au/ZnO-D-H. The testing results showed that the Au/ZnO-F-O catalyst containing maximum of Au3+ possesses the optimal activity with 1.8 × 10-2 s-1 of specific activity at 200 °C, around 16.5-fold of that for Au/ZnO-D-H. More interestingly, the specific rate at 200 °C and the average conversion/selectivity in the entire operating temperature range are well correlated with the redox states of the Au species, indicating that Au3+ sites are more active for acetylene hydrogenation. A plausible explanation is that the Au3+ species not only facilitate acetylene adsorption via electrostatic interactions but also favor the heterolysis of H2 via constructing frustrated Lewis pairs with O.

Carbon/Polymer Bilayer-Coated Si-SiOx Electrodes with Enhanced Electrical Conductivity and Structural Stability.

Si-based electrodes offer exceptionally high capacity and energy density for lithium-ion batteries (LIBs),but suffer from poor structural stability and electrical conductivity that hamper their practical applications. To tackle these obstacles, we design a C/polymer bilayer coating deposited on Si-SiOx microparticles. The inner C coating is used to improve electrical conductivity. The outer C-nanoparticle-reinforced polypyrrole (CNP-PPy) is a polymer matrix composite that can minimize the volumetric expansion of Si-SiOx and enhance its structural stability during battery operation. Electrodes made of such robust Si-SiOx@C/CNP-PPy microparticles exhibit excellent cycling performance: 83% capacity retention (794 mAh g-1) at a 2 C rate after more than 900 cycles for a coin-type half cell, and 80% capacity retention (with initial energy density of 308 Wh kg-1) after over 1100 cycles for a pouch-type full cell. By comparing the samples with different coatings, an in-depth understanding of the performance enhancement is achieved, i.e., the C/CNP-PPy with cross-link bondings formed in the bilayer coating plays a key role for the improved structural stability. Moreover, a full battery using the Si-SiOx@C/CNP-PPy electrode successfully drives a car model, demonstrating a bright application prospect of the C/polymer bilayer coating strategy to make future commercial LIBs with high stability and energy density.

Bi-functional nitrogen-doped carbon protective layer on three-dimensional RGO/SnO2 composites with enhanced electron transport and structural stability for high-performance lithium-ion batteries.

Three-dimensional reduced graphene oxide@SnO2@nitrogen-doped carbon (3DG@SnO2@N-C) composites are designed as high efficiency anode materials for lithium-ion batteries. The SnO2 particle size, surface area and pore size distribution of the 3DG@SnO2@N-C could be simply controlled by altering the GO dosages. The optimized 3DG@SnO2@N-C electrode demonstrates a reversible capacity of 1349.5 mAh g-1 after 100 cycles at the current density of 100 mA g-1. Based on the structural and electrochemical dynamic tests, the bi-functional N-doped carbon coating layer could serve as both conductive channel for electron transport and as buffer layer to alleviate the volume change of embedded SnO2 NPs. In addition, the cross-linked conducting 3DG with porous structure attributes to the reduced electron transport and Li ion diffusion resistances, which finally leads to the enhanced cycling stability and rate performances.

Hollow K0.27MnO2 Nanospheres as Cathode for High-Performance Aqueous Sodium Ion Batteries.

Hollow K0.27MnO2 nanospheres as cathode material were designed for aqueous sodium ion batteries (SIBs) using polystyrene (PS) as a template. The samples were systematically studied by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. As cathode materials for aqueous SIBs, the hollow structure can effectively improve the sodium storage property. A coin cell with hollow K0.27MnO2 as cathode and NaTi2(PO4)3 as anode exhibits a specific capacity of 84.9 mA h g(-1) at 150 mA g(-1), and the capacity of 56.6 mA h g(-1) is still maintained at an extremely high current density of 600 mA g(-1). For full cell measurement at the current density of 200 mA g(-1), 83% capacity retention also can be attained after 100 cycles. The as-designed hollow K0.27MnO2 nanospheres demonstrate long cyclability and high rate capability, which grant the potential for application in advanced aqueous SIBs.