A sub-10 μm Ion Conducting Membrane with an Ultralow Area Resistance for a High-Power Density Vanadium Flow Battery

With the outstanding features of high safety, high efficiency, and long lifespan, the vanadium flow battery (VFB) is well-suited for large-scale energy storage; however, it suffers from low power density. The high ion conductivity of membranes is very important to increase the performance of VFBs at high current densities and improve their power density. Here, we show a highly conductive free-standing sub-10 μm polybenzimidazole (PBI) membrane. The decrease in the membrane thickness contributes to shorter ion-transport pathways and lower resistance. The relatively loose cross-linked structure of the thin membrane provides sufficient free volume for ion transport. According to these results, the membrane exhibits an ultralow area resistance of 0.04 Ω cm2, much lower than that of commercial Nafion 115 membrane (0.20 Ω cm2), making the ion conductivity superior. Additionally, the sub-10 μm PBI membrane also shows a very high tensile strength of 45.5 MPa and high ion selectivity. The VFB assembled with a sub-10 μm PBI membrane delivers a high energy efficiency of approximately 80% at a high current density of 200 mA cm–2 and can run stably for more than 500 cycles without obvious performance decay. The increased performance of the VFB at a very high current density of 200 mA cm–2 contributes to its higher power density. Therefore, it is an available way to adopt free-standing sub-10 μm PBI membranes with high conductivity, selectivity, and mechanical stability to improve the power density of VFBs. Similarly, the application of it will also accelerate the practical application of VFB energy storage technology

Table_1_Bracelet-Like Ni0.4Cu0.6O Microstructure Composed of Well-Aligned Nanoplatelets as a Superior Catalyst to the Hydrolysis of Ammonia Borane.DOCX

The development of novel catalysts with both high catalytic activity and low cost toward the hydrolysis of ammonia borane is an important subject in the field of hydrogen energy. In this communications, NixCu1−xO microstructures with different morphology have been synthesized and their catalytic activities in AB hydrolysis is studied. It's found that bracelet-like nanoplatelets were obtained at x = 0.4 and exhibit highest catalytic performance with turnover frequency of 33.43 molhydrogen min−1molcat-1, which much higher than those of most of CuNi-based catalysts in the literature. Pronounced synergistic effects between CuO and NiO in AB hydrolysis also have been observed. Due to the superior catalytic performance and cheapness, the prepared bracelet-like nanoplatelets Ni0.4Cu0.6O catalysts can be a strong catalyst candidate in AB hydrolysis.</p

A High Energy Density Bromine-Based Flow Battery with Two-Electron Transfer

Bromine-based flow batteries have been widely used for large-scale energy storage because of their attractive features of low cost and high redox potential. At present, bromine redox chemistry mainly based on a single-electron electrochemical reaction of Br2/Br– and a higher valence to Br+ suffers from serious side reactions. Herein, a two-electron-transfer electrochemical reaction was realized by employing BrCl2–/Br– as a positive redox couple. In this design, the side reaction of Br+ could be inhibited by the introduction of Cl– via the complexing effect in an acid environment. As a proof of concept, by using TiO2+/Ti3+ as a negative redox couple, a Ti–Br–Cl flow battery (TBCFB) demonstrated a discharge capacity up to 96 Ah L–1 and continuously ran for more than 300 cycles without obvious performance decay. With the high redox potential, high energy density, and high stability, the BrCl2–/Br–-based flow batteries demonstrate very promising perspectives for large-scale energy storage applications

Magnesium/Lithium-Ion Hybrid Battery with High Reversibility by Employing NaV₃O₈·1.69H₂O Nanobelts as a Positive Electrode

Recently, magnesium-ion batteries (MIBs) have been under remarkable research focus owing to their appealingly high energy density and natural abundance of magnesium. Nevertheless, MIBs exhibit a very limited performance because of sluggish solid-state Mg²⁺ ion diffusion and high polarizability, which hinder their progress toward commercialization. Herein, we report a Mg²⁺/Li⁺ hybrid-ion battery (MLIB) with NaV₃O₈·1.69H₂O (NVO) nanobelts synthesized at room temperature working as the positive electrode. In the hybrid-ion system, Li⁺ intercalates/deintercalates along with a small amount of Mg²⁺ adsorption at the NVO cathode, whereas the anode side of the cell is dominated by Mg²⁺ deposition/dissolution. As a result, the MLIB exhibits a much higher rate capability (i.e., 446 mA h g^–1 at 20 mA g^–1) than the previously reported MLIBs. MLIB maintains a high specific capacity of 200 mA h g^–1 at 80 mA g^–1 for 150 cycles, showing excellent stability. Moreover, the effect of different Li-ion concentrations (i.e., 0.5–2.0 M) in the electrolyte and cutoff voltage (ranging from 2 to 2.6 V) on the specific capacities are investigated. The current study highlights a strategy to exploit the Mg²⁺/Li⁺ hybrid electrolyte system with various electrode materials for high-performance MIBs

Structure of Hydrated Poly(d,l-lactic acid) Studied with X-ray Diffraction and Molecular Simulation Methods

The effect of hydration on the molecular structure of amorphous poly­(d,l-lactic acid) (PDLLA) with 50:50 L-to-D ratio has been studied by combining experiments with molecular simulations. X-ray diffraction measurements revealed significant changes upon hydration in the structure functions of the copolymer. Large changes in the structure functions at ∼10 days of incubation coincided with the large increase in the water uptake from ∼1 to ∼40% and the formation of voids in the film. Computer modeling based on the recently developed TIGER2/TIGER3 mixed sampling scheme was used to interpret these changes by efficiently equilibrating both dry and hydrated models of PDLLA. Realistic models of bulk amorphous PDLLA structure were generated as demonstrated by close agreement between the calculated and the experimental structure functions. These molecular simulations were used to identify the interactions between water and the polymer at the atomic level including the change of positional order between atoms in the polymer due to hydration. Changes in the partial O–O structure functions, about 95% of which were due to water–polymer interactions, were apparent in the radial distribution functions. These changes, and somewhat smaller changes in the C–C and C–O partial structure functions, clearly demonstrated the ability of the model to capture the hydrogen-bonding interactions between water and the polymer, with the probability of water forming hydrogen bonds with the carbonyl oxygen of the ester group being about 4 times higher than with its ether oxygen

Activated Carbon Fiber Paper Based Electrodes with High Electrocatalytic Activity for Vanadium Flow Batteries with Improved Power Density

Vanadium flow batteries (VFBs) have received high attention for large-scale energy storage due to their advantages of flexibility design, long cycle life, high efficiency, and high safety. However, commercial progress of VFBs has so far been limited by its high cost induced by its low power density. Ultrathin carbon paper is believed to be a very promising electrode for VFB because it illustrates super-low ohmic polarization, however, is limited by its low electrocatalytic activity. In this paper, a kind of carbon paper (CP) with super-high electrocatalytic activity was fabricated via a universal and simple CO₂ activation method. The porosity and oxygen functional groups can be easily tuned via this method. The charge transfer resistance (denoting the electrochemical polarization) of a VFB with CP electrode after CO₂ activation decreased dramatically from 970 to 120 mΩcm². Accordingly, the energy efficiency of a VFB with activated carbon paper as the electrode increased by 13% as compared to one without activation and reaches nearly 80% when the current density is 140 mAcm^–2. This paper provides an effective way to prepare high-performance porous carbon electrodes for VFBs and even for other battery systems

Advanced Porous Membranes with Tunable Morphology Regulated by Ionic Strength of Nonsolvent for Flow Battery

A simple salt-induced phase separation method is presented to prepare porous polybenzimidazole (PBI) membranes with tunable morphology for vanadium flow batteries (VFBs). This method is based on the traditional nonsolvent-induced phase separation (NIPS) method where salt is introduced into the coagulation bath to change the ionic strength of the nonsolvent. The change of ionic strength will affect the phase separation rate, and finally, the morphology of porous membranes is well tuned from finger-like voids to sponge-like pores in site. The membrane with sponge-like pores created multiple barriers to the transfer of vanadium ions, offering the membrane with superhigh selectivity; meanwhile, spongy cells filled with sulfuric acid could provide the membrane with high proton conductivity. As a result, the membrane with sponge-like pores demonstrated a much better performance than that with finger-like voids. The resultant sponge-like porous PBI membrane exhibited a very impressive VFB performance with an energy efficiency of 89.9% at a current density of 80 mA cm–2, which was close to the highest values ever reported. The battery kept very stable performance even after continuously running for more than 10000 cycles at 160 mA cm–2, showing excellent stability. This paper provides an easy to scale up and environment-friendly method to fabricate high-performance porous membranes with tunable morphology

Sequential DNA-Encoded Building Block Fusion for the Construction of Polysubstituted Pyrazoline Core Libraries

The construction of chemical libraries containing polysubstituted pyrazoline scaffolds is highly desirable for the discovery of novel chemical ligands for biological targets. Herein, we report a sequential DNA-encoded synthesis strategy for polysubstituted pyrazoline heterocycles, which fuses a broad panel of aldehydes, aryl amines, and alkenes as building blocks. Furthermore, mock library synthesis and selection demonstrated the ability of the method to produce DNA-encoded focused libraries with highly functionalized pyrazoline cores

Multifunctional Membranes for Solvent Resistant Nanofiltration and Pervaporation Applications Based on Segmented Polymer Networks

Hydrophilic bis(acrylate)-terminated poly(ethylene oxide) was used as macromolecular cross-linker of different hydrophobic polyacrylates for the synthesis of amphiphilic segmented polymer networks (SPNs). Multifunctional composite membranes with thin SPN toplayers were prepared by in situ polymerization. As the support consisted of hydrolyzed polyacrylonitrile, the high chemical resistance of the composite membrane allowed applications of the SPN-based membranes in solvent-resistant nanofiltration (SRNF) and pervaporation (PV). The membranes show very high retention on Rose Bengal (RB) in different solvents, especially in strong swelling solvents such as tetrahydrofuran (THF) and dimethylformamide (DMF). The membranes were also tested in pervaporation for dehydration of ethanol and isopropanol (IPA). The selectivity of the membranes greatly depends on the composition or the ratio of the hydrophilic and hydrophobic phases of the SPN

Bi-Modified Zn Catalyst for Efficient CO₂ Electrochemical Reduction to Formate

Developing efficient and low-cost catalysts is the key part for electrochemical reduction of CO2, and the bimetallic approach is a cost-effective strategy to find promising electrocatalysts for CO2 reduction. Herein, a low-cost Bi-modified Zn catalyst with nanoparticle morphologies was developed for electrochemical CO2 reduction to formate. The catalyst was prepared through a surface modification with a simple method. A maximum formate Faradaic efficiency of 94% was achieved at −0.8 V vs RHE. The high density of active sites offered by the metal–metal bifunctional interfaces and grain boundaries is the main factor determining the excellent performance of the Zn-Bi bimetallic catalyst