Transitional metal sulfide ultrathin structures present various advantageous functional properties and hold great promise in energy conversion reactions, but their facile and large-scale preparation are still challenging. Herein, a facile strategy is developed for the preparation of ultrathin MoS 2 nanosheets via an organic matrix-facilitated deposition followed by ultrasonic exfoliation strategy. MoS 2 nanosheets with lateral dimensions around 100 nm and thickness around 10–20 nm are facilely obtained. They present the typical multiple absorbance indicating the unique band structure characteristics of MoS 2 2D nanosheets. Furthermore, the electronic structures of the ultrathin MoS 2 nanosheets can be tuned via controlling their immediate environment in assemblies. In the layer-by-layer interfacial assemblies of (PEDOT:PSS/MoS 2 )n multilayers, the catalytic efficiency of MoS 2 nanosheets is enhanced by a charge transfer process as corroborated by DFT simulation. The catalytic capabilities of the assemblies are optimized by the well-controlled layer-by-layer process and present effective and stable electrochemical HER properties. We expect that this fabrication strategy of 2D MoS 2 nanosheets promote the research of functional materials based on MoS 2 nanosheets and can be extended to the preparation of other nanosheet materials.
Zhen Lin,Qiugen Zhang,Yan Qu,Mengmeng Chen,Faizal Soyekwo,Chenxiao Lin,Aimei Zhu,Qinglin Liu
Polyelectrolyte membranes provide a highly promising platform for an efficient and sustainable nanofiltration (NF) process. The challenge is to prepare polyelectrolyte NF membranes with high permeation. Herein, we report a novel strategy to fabricate a polyelectrolyte membrane via a layer-by-layer (LBL) self-assembly technique with a Ni(OH)2 nanosheet sacrificial layer for a fast NF process. The sacrificial layer helps to deposit a LBL assembled polyelectrolyte layer directly on a microfiltration (MF) substrate and thus results in the formation of a membrane with tiny filtration resistance. Meanwhile, the surface charges and thickness of the membranes can be adjusted facilely by the number of assembled layers. The resultant membranes show excellent NF performances with a high water flux of up to 466 L m−2 h−1 bar−1, perfect rejection for organic dye molecules and moderate salt rejection (88.2% MgSO4). Typically, the 570 nm-thick membrane has the water flux of 198 L m−2 h−1 bar−1, 98% rejection for dyes (Mw 373.9) and 81.3% rejection for MgCl2. Furthermore, the membrane has a good rejection and anti-fouling ability for organic molecules with similar charges. The newly developed strategy has wide application in the fabrication of highly permeable polyelectrolyte membranes.
Jiawei Liu,Abdisamad Ahmed Abdirahman,Xuliang Wang,Yanlei Su
A method of assembling nanofilms for nanofiltration (NF) composite membranes with ultra-high desalination performance was developed in this work. A series of graphene quantum dots enhanced polyamide (GPA) nanofilms were primarily prepared via support-free interfacial polymerization. Subsequently, the NF composite membranes with two GPA nanofilms (GPA-GPA) layer-by-layer (LBL) assembly were elaborately designed to achieve effective desalination process. The residual amine groups and acyl chloride groups on the surfaces of GPA nanofilms reasonably formed a nascent polyamide (PA) interlayer between two functional layers. The separation performance of GPA-GPA assembly membranes was dramatically developed through the in-situ formed PA interlayer with network pore structure . Most of assembled NF membranes exhibited Na 2 SO 4 rejection rate above 99.5%, and the permeance was above 20.0 L m −2 h −1 bar −1 . This creative strategy of in-situ constructing PA interlayer opened up an innovative path for the design of NF membranes with excellent desalination performance.
Layer-by-layer (LbL) assembly technology is a facile method for constructing thin film composite membrane. Herein, a novel nanofiltration (NF) membrane was prepared by LbL assembly of polyethyleneimine (PEI) and sodium lignosulfonate (LS) followed by cross-linking. The surface composition, morphology, and property of PEI/LS bilayer were detailedly investigated by FTIR/ATR, XPS, SEM, AFM, and water contact angle test. The PEI/LS bilayer full of amino and hydroxyl groups presents increased roughness and improved hydrophilicity. Moreover, the NF performance of PEI/LS LbL assembly membranes can be modulated by bilayer number, polyelectrolyte concentration, and salt content. The water flux reduced while the salt rejection greatly improved as increasing the bilayer numbers, PEI concentration, or NaCI content. More than 95% MgSO 4 and MgCI 2 , as well as 80% NaCI can be rejected by a NF membrane prepared by 6 PEI/LS bilayers, 1 wt% PEI, 0.5 wt% LS, and 1 mol/L NaCI. Furthermore, this NF membrane can be used to remove more than 95% heavy metal ions (Cd 2+ , Zn 2+ , Mn 2+ , Cr 2+ , Cu 2+ , and Ni 2+ ). This work proposed a promising NF membrane by using PEI/LS as low cost polyelectrolytes and facile LbL assembly method, which should receive much attention in water purification.
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