Internal Surface Modification of MFI-Type Zeolite Membranes for High Selectivity and High Flux for Hydrogen

MFI-type zeolite membranes were modified by depositing molecular silica at a small number of active sites in the internal surface by in situ catalytic cracking of silane precursor. The limited silica deposition reduced the effective size of the zeolitic channels that dramatically enhanced the H2 selectivity without causing a large increase in H2 transport resistance. The modified zeolite membrane achieved an extraordinary H2/CO2 permselectivity of 141 with a high H2 permeance of 3.96 × 10−7 mol/m2·s·Pa at 723 K. The effect of pore modification on the gas transport behavior was studied on the basis of single gas permeation data

Interferometric Study on the Adsorption-Dependent Refractive Index of Silicalite Thin Films Grown on Optical Fibers

Interferometric Study on the Adsorption-Dependent Refractive Index of Silicalite Thin Films Grown on Optical Fiber

Determining Dielectric Constants for Complex Solvent Mixtures by Microwave Sensing and Model Prediction

The frequency-dependent dielectric constant is a basic fluid property that is currently challenging to determine for complex liquid mixtures. Here, we report the determination of effective dielectric constants for various solvent mixtures under flow conditions using a simple in-line microwave Fabry–Pérot interferometer cable sensor. An ideal solution model-based mixing rule has been established and demonstrated for significantly improved prediction of dielectric constants for single-phase solvent mixtures. However, the current mixing rules exhibit large deviations for immiscible water/oil dispersions apparently because of the effects of strong interfacial polarizations on the overall mixture polarizability that are not accounted for by the models

Perovskite-Type Oxide Thin Film Integrated Fiber Optic Sensor for High-Temperature Hydrogen Measurement

Small size fiber optic devices integrated with chemically sensitive photonic materials are emerging as a new class of high-performance optical chemical sensor that have the potential to meet many analytical challenges in future clean energy systems and environmental management. Here, we report the integration of a proton conducting perovskite oxide thin film with a long-period fiber grating (LPFG) device for high-temperature in situ measurement of bulk hydrogen in fossil- and biomass-derived syngas. The perovskite-type Sr(Ce0.8Zr0.1)Y0.1O2.95 (SCZY) nanocrystalline thin film is coated on the 125 μm diameter LPFG by a facile polymeric precursor route. This fiber optic sensor (FOS) operates by monitoring the LPFG resonant wavelength (λR), which is a function of the refractive index of the perovskite oxide overcoat. At high temperature, the types and population of the ionic and electronic defects in the SCZY structure depend on the surrounding hydrogen partial pressure. Thus, varying the H2 concentration changes the SCZY film refractive index and light absorbing characteristics that in turn shifts the λR of the LPFG. The SCZY-coated LPFG sensor has been demonstrated for bulk hydrogen measurement at 500 °C for its sensitivity, stability/reversibility, and H2-selectivity over other relevant small gases including CO, CH4, CO2, H2O, and H2S, etc

Balancing Osmotic Pressure of Electrolytes for Nanoporous Membrane Vanadium Redox Flow Battery with a Draw Solute

Vanadium redox flow batteries with nanoporous membranes (VRFBNM) have been demonstrated to be good energy storage devices. Yet the capacity decay due to permeation of vanadium and water makes their commercialization very difficult. Inspired by the forward osmosis (FO) mechanism, the VRFBNM battery capacity decrease was alleviated by adding a soluble draw solute (e.g., 2-methylimidazole) into the catholyte, which can counterbalance the osmotic pressure between the positive and negative half-cell. No change of the electrolyte volume has been observed after VRFBNM being operated for 55 h, revealing that the permeation of water and vanadium ions was effectively limited. Consequently, the Coulombic efficiency (CE) of nanoporous TiO₂ vanadium redox flow battery (VRFB) was enhanced from 93.5% to 95.3%, meanwhile, its capacity decay was significantly suppressed from 60.7% to 27.5% upon the addition of soluble draw solute. Moreover, the energy capacity of the VRFBNM was noticeably improved from 297.0 to 406.4 mAh remarkably. These results indicate balancing the osmotic pressure via the addition of draw solute can restrict pressure-dependent vanadium permeation and it can be established as a promising method for up-scaling VRFBNM application

PEGylation-Enabled Extended Cyclability of a Non-aqueous Redox Flow Battery

Non-aqueous redox flow batteries (RFBs) are promising energy storage devices owing to the broad electrochemical window of organic solvents. Nonetheless, the wide application of these batteries has been limited by the low stability and limited solubility of organic materials, as well as the insufficient ion conductivity of the cell separators in non-aqueous electrolytes. In this study, two viologen analogues with poly­(ethylene glycol) (PEG) tails are designed as anolytes for non-aqueous RFBs. The PEGylation of viologen not only enhances the solubility in acetonitrile but also increases the overall molecular size for alleviated crossover. In addition, a composite nanoporous aramid nanofiber separator, which allows the permeation of supporting ions while inhibiting the crossover of the designer viologens, is developed using a scalable doctor-blading method. Paired with ferrocene, the full organic material-based RFB presents excellent cyclability (500 cycles) with a retention capacity per cycle of 99.93% and an average Coulombic efficiency of 99.3% at a current density of 2.0 mA/cm2. The high performance of the PEGylated viologen validates the potential of the PEGylation strategy for enhanced organic material-based non-aqueous RFBs

Proton-Selective Ion Transport in ZSM‑5 Zeolite Membrane

The ionic ZSM-5 zeolite membranes were investigated for proton-selective ion separation in electrolyte solutions relevant to redox flow batteries. The zeolite membrane achieved exceptional selectivity for proton over V⁴⁺ (VO²⁺), Cr²⁺, and Fe²⁺ via size-exclusion at the zeolitic channel openings, and remarkably low area specific resistance resulted from its hydrophilic surface, copious extraframework protons, and micron-scale thickness. The ZSM-5 membrane, as a new type of ion separator, demonstrated substantially reduced self-discharge rates and enhanced efficiencies for the all-vanadium and iron–chromium flow batteries as compared to the benchmark Nafion membrane. Findings of this research show that ionic microporous zeolite membranes can potentially overcome the challenge of trade-off between ion selectivity and conductivity associated with conventional polymeric ion separators

High-Efficiency Miniaturized Ultrasonic Nebulization Sample Introduction System for Elemental Analysis of Microvolume Biological Samples by Inductively Coupled Plasma Quadrupole Mass Spectrometry

Sensitive and high-throughput analysis of trace elements in volume-limited biological samples is highly desirable for clinical research and health risk assessments. However, the conventional pneumatic nebulization (PN) sample introduction is usually inefficient and not well-suited for this requirement. Herein, a novel high-efficiency (nearly 100% sample introduction efficiency) and low-sample-consumption introduction device was developed and successfully coupled with inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). It consists of a micro-ultrasonic nebulization (MUN) component with an adjustable nebulization rate and a no-waste spray chamber designed based on fluid simulation. The proposed MUN-ICP-QMS could achieve sensitive analysis at a low sampling rate of 10 μL min–1 with an extremely low oxide ratio of 0.25% where the sensitivity is even higher comparing to PN (100 μL min–1). The characterization results indicate that the higher sensitivity of MUN is attributed to the smaller aerosol size, higher aerosol transmission efficiency, and improved ion extraction. In addition, it offers a fast washout (20 s) and reduced sample consumption (as low as 7 μL). The absolute LODs of the studied 26 elements by MUN-ICP-QMS are improved by 1–2 orders of magnitude compared with PN-ICP-QMS. The accuracy of the proposed method was validated by the analysis of human serum, urine, and food-related certified reference materials. Furthermore, preliminary results of serum samples from patients with mental illnesses demonstrated its potential in the field of metallomics

High-Efficiency Miniaturized Ultrasonic Nebulization Sample Introduction System for Elemental Analysis of Microvolume Biological Samples by Inductively Coupled Plasma Quadrupole Mass Spectrometry

Sensitive and high-throughput analysis of trace elements in volume-limited biological samples is highly desirable for clinical research and health risk assessments. However, the conventional pneumatic nebulization (PN) sample introduction is usually inefficient and not well-suited for this requirement. Herein, a novel high-efficiency (nearly 100% sample introduction efficiency) and low-sample-consumption introduction device was developed and successfully coupled with inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). It consists of a micro-ultrasonic nebulization (MUN) component with an adjustable nebulization rate and a no-waste spray chamber designed based on fluid simulation. The proposed MUN-ICP-QMS could achieve sensitive analysis at a low sampling rate of 10 μL min–1 with an extremely low oxide ratio of 0.25% where the sensitivity is even higher comparing to PN (100 μL min–1). The characterization results indicate that the higher sensitivity of MUN is attributed to the smaller aerosol size, higher aerosol transmission efficiency, and improved ion extraction. In addition, it offers a fast washout (20 s) and reduced sample consumption (as low as 7 μL). The absolute LODs of the studied 26 elements by MUN-ICP-QMS are improved by 1–2 orders of magnitude compared with PN-ICP-QMS. The accuracy of the proposed method was validated by the analysis of human serum, urine, and food-related certified reference materials. Furthermore, preliminary results of serum samples from patients with mental illnesses demonstrated its potential in the field of metallomics