Mesoporous Interlayer Research Articles

Ultrathin sulfonated mesoporous interlayer facilitates to prepare highly-permeable polyamide nanofiltration membranes

Highly-permeable nanofiltration (NF) membranes are strongly required and have become more crucial with increasing concerns in water treatment and purification. Herein a versatile approach is developed to prepare a highly-permeable polyamide (PA) NF membrane via the traditional interfacial polymerization (IP) process facilitated by an ultrathin sulfonated mesoporous interlayer. A series of the interlayers with a thickness of 110–250 nm and a cut-off around 12 nm is prepared and employed to prepare the PA NF membrane from piperazine (PIP) and 1, 3, 5-benzotriformyl chloride (TMC). Influence factors on the membrane preparation including the interlayer thickness and monomer concentrations are investigated in detail. Sulfonic groups on the interlayer greatly facilitate the PIP adsorption and thus increase the PIP storage in the interlayer, resulting in the formation of a defect-free, 10–50 nm-thick PA membrane at a low monomer concentration. The thickness and surface roughness of PA layer increase with the interlayer thickness simultaneously. Typically, the 40 nm-thick PA membrane has a pure water permeance of high to 36.3 L m−2 h−1 bar−1 with a Na2SO4 rejection of 98.5%. The newly developed approach has a wide application in the preparation of highly-permeable PA membranes for various fields including water treatment and chemical separation.

Asymmetric and hierarchical porous carbon membranes prepared by a single-step soft-templated method

A facile single-step method was developed to prepare carbon membranes derived from novalac phenol–formaldehyde resin as a carbon precursor and Pluronic® F108 (EO132–PO50–EO132) and polyethylene glycol as the soft template. In a single sintering-step, an asymmetric membrane was formed with a very thin top layer followed mesoporous interlayer supported on a macroporous support. The top separating layer was characterized by closely packed carbon particles while the interlayer is consisted of disordered and loosely packed carbon particles, containing large gaps thus leading to hierarchical structures. The carbon membrane achieved H2/N2 permselectivity up to 92, far above the Knudsen selectivity suggesting the molecular sieving mechanism.

Methylammonium-free, high-performance, and stable perovskite solar cells on a planar architecture.

Currently, perovskite solar cells (PSCs) with high performances greater than 20% contain bromine (Br), causing a suboptimal bandgap, and the thermally unstable methylammonium (MA) molecule. Avoiding Br and especially MA can therefore result in more optimal bandgaps and stable perovskites. We show that inorganic cation tuning, using rubidium and cesium, enables highly crystalline formamidinium-based perovskites without Br or MA. On a conventional, planar device architecture, using polymeric interlayers at the electron- and hole-transporting interface, we demonstrate an efficiency of 20.35% (stabilized), one of the highest for MA-free perovskites, with a drastically improved stability reached without the stabilizing influence of mesoporous interlayers. The perovskite is not heated beyond 100°C. Going MA-free is a new direction for perovskites that are inherently stable and compatible with tandems or flexible substrates, which are the main routes commercializing PSCs.

Hierarchical layered double hydroxides with Ag nanoparticle modification for ethanol sensing

Layered double hydroxides (LDHs) have recently been revealed to be promising in gas sensor applications due to their compositional flexibility and unique 2D-interlayer channel for gas diffusion and adsorption. This work demonstrates highly porous hierarchical LDHs containing Mg2+ and Al3+ (MgAl-LDHs) for ethanol sensing at room temperature. These MgAl-LDHs, with unique flower-like hierarchical structure and mesoporous interlayer, were synthesized hydrothermally using sodium dodecyl sulfate as soft template as well as intercalating agent. Further modification by discrete Ag nanoparticles (NPs) was achieved via an environmentally friendly glucose-reduction method to improve the gas-sensing response of the LDH-based sensor. It is found that the hierarchical MgAl-LDHs show potential in sensing ethanol gas with rapid dynamic characteristics at room temperature; their response magnitude towards ethanol can be enhanced significantly by Ag NP modification. The gas-response value of the Ag-modified MgAl-LDH sensor is about twice that of pristine MgAl-LDH sensors, towards 5–200 ppm ethanol at room temperature. Meanwhile, rapid response-recovery characteristics are achieved, with response and recovery times shorter than 10 and 50 s, respectively. The satisfactory sensing performance and remarkable response enhancement by Ag NP modification are demonstrated in terms of the unique microstructure of the hierarchical MgAl-LDHs and a constructed conductive effect model of Ag functionalized LDHs.

A New Conceptual Cathode and Separator Design Enabling High Energy Density Lithium-Sulfur Batteries

Significant improvement of lithium ion batteries (LIBs) performances has been achieved with a rapid advance of portable electronic devices over the past quarter century. With a growing demand for high performance power sources, world-wide efforts have been devoted to the development of an alternative battery system to replace current LIBs which face performance limitation in terms of capacity and energy density. Recently, lithium-sulfur (Li-S) batteries have received an unprecedented attention owing to their great potentials such as a large theoretical capacity of sulfur, low toxicity and low cost. As cutting-edge nanotechnologies (e.g., C-S composite concept, mesoporous interlayer) have been employed to Li-S batteries, their performances have been dramatically improved for the past two decades. Despite such remarkable progress, there have remained many issues (i.e., limited cycling performance and low rate properties) which should be addressed for successful commercialization of Li-S batteries. In addition, most approaches to solve those problems need so complex and expensive processes which are so hard to implement them to practical mass production. Herein, we report a facile and cost-effective approach for the development of high-performance Li-S batteries. Through combining a functional separator to a high-sulfur-loading cathode, which can mitigate the active material loss and confine polysulfide ions within a specific space ensuring a long cycle life, high-performance Li-S batteries are fabricated and their characteristic features are intensively investigated.

Preparation of an asymmetric microporous carbon membrane for ultrafiltration separation: application to the treatment of industrial dyeing effluent

An asymmetric tubular carbon membrane with an ultrafiltration microporous top layer has been prepared using thermosetting phenolic resin and carbon black (CB) as carbon precursors. The membrane was composed of a mesoporous interlayer with an average pore size of 0.6μm deposited by slip casting process on the inner face of a macroporous support. The microporous top layer was deposited by the same process using suspensions of commercial CB powder (44nm average pores size). An initial ultrafiltration membrane with an average pore size of 7.9nm and a thickness of 8.34μm was formed requiring 10 min casting time and a curing–carbonization cycle at 700°C under nitrogen atmosphere. An approach consisting of repeating casting–carbonization cycle was adopted to correct the defects that appeared at the surface. Results showed that an UF-corrected membrane denominated UF-C4 was successfully prepared by adding only one layer after its composition and conditions of deposition were determined. A crack-free UF membrane with a thickness layer of 12.6 μm, a mean pores size of 5.3 nm, and a molecular weight cut-off of 90 kDa was then obtained using only 6 min casting time. It was found that this membrane could be applied efficiently to the treatment of industrial dyeing effluent.

Separation mechanism in dehydration of water/organic binary liquids by pervaporation through microporous silica

The pervaporation properties of two microporous three-layer stacked ceramic membranes that differ only with respect to the nature of the mesoporous interlayer are discussed. The adsorption–diffusion model and Maxwell–Stefan theory are applied to explain the influence of process parameters on the pervaporation of selected binary liquids. The temperature, feed concentration and chemical nature of the permeating species were varied. The membrane system α-Al 2O 3/γ-Al 2O 3/microporous SiO 2 was found to have the highest selectivity for dewatering of alcohols. This is due to a combination of small pores in the microporous silica layer, and the hydrophilicity of this layer. When γ-Al 2O 3 was replaced by mesoporous anatase, lower separation factors were obtained. The hydrophilicity of the silica top layer appears to be influenced by the nature of the underlying mesoporous supporting layer.

Alumina and titania multilayer membranes for nanofiltration: preparation, characterization and chemical stability

The preparation and characterization of porous ceramic multilayer nanofiltration (NF) membranes is described. During preparation, special care was given to each sub-layer that forms a part of the multilayer configuration: the macroporous substrate, the membrane interlayers and the NF toplayers. High-quality macroporous supports are prepared from α-Al 2O 3. Three types of colloidal sol–gel derived mesoporous interlayers are considered: Al 2O 3, TiO 2 and mixed Al 2O 3–TiO 2. The active NF toplayer is a very thin and fine textured polymeric TiO 2 toplayer. Optimized α-Al 2O 3/γ-Al 2O 3/anatase and α-Al 2O 3/anatase/anatase multilayer configurations show high retentions for relatively small organic molecules (molecular weight cut-off <200). Different membrane layers have very different crystallographic properties resulting in a considerably different chemical stability. Corrosion measurements showed that application of a multilayer configuration including weakly crystallized γ-Al 2O 3 layers is restricted to mild aqueous media (pH 3–11) or non-aqueous media (organic solvents). For NF applications in aqueous media with a lower or higher pH, the multilayer membrane composed of anatase on a α-Al 2O 3 support is to be preferred.