Vaibhav Kulshrestha

SGO/SPES-Based Highly Conducting Polymer Electrolyte Membranes for Fuel Cell Application

Proton-exchange membranes (PEMs) consisting of sulfonated poly(ether sulfone) (SPES) with enhanced electrochemical properties have been successfully prepared by incorporating different amount of sulfonated graphene oxide (SGO). Composite membranes are tested for proton conductivity (30-90 °C) and methanol crossover resistance to expose their potential for direct methanol fuel cell (DMFC) application. Incorporation of SGO considerably increases the ion-exchange capacity (IEC), water retention and proton conductivity and reduces the methanol permeability. Membranes have been characterized by FTIR, XRD, DSC, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in composite membranes are established by FTIR. The distribution of SGO throughout the membrane matrix has been examined using SEM and TEM and found to be uniform. The maximum proton conductivity has been found in 5% SGO composite with higher methanol crossover resistance.

Dramatic Improvement in Water Retention and Proton Conductivity in Electrically Aligned Functionalized CNT/SPEEK Nanohybrid PEM

Nanohybrid membranes of electrically aligned functionalized carbon nanotube f CNT with sulfonated poly ether ether ketone (SPEEK) have been successfully prepared by solution casting. Functionalization of CNTs was done through a carboxylation and sulfonation route. Further, a constant electric field (500 V·cm(-2)) has been applied to align CNTs in the same direction during the membrane drying process. All the membranes are characterized chemically, thermally, and mechanically by the means of FTIR, DSC, DMA, UTM, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in hybrid membranes are established by FTIR. Physicochemical measurements were done to analyze membrane stability. Membranes are evaluated for proton conductivity (30-90 °C) and methanol crossover resistance to reveal their potential for direct methanol fuel cell application. Incorporation of f CNT reasonably increases the ion-exchange capacity, water retention, and proton conductivity while it reduces the methanol permeability. The maximum proton conductivity has been found in the S-sCNT-5 nanohybrid PEM with higher methanol crossover resistance. The prepared membranes can be also used for electrode material for fuel cells and batteries.

Preparation of graphene oxide nano-composite ion-exchange membranes for desalination application

Nano-composite ion-exchange membranes (IEMs) consisting of graphene oxide (GO) (0.5, 1, 2, 5 and 10%) (w/w) and sulfonated polyethersulfone (SPES) of thickness 180 μm are prepared with enhanced electrochemical properties. In particular, the transport properties of SPES are favourably manipulated by the incorporation of GO. Intermolecular interactions between the components in composite membranes are established by FTIR. Membranes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) which showed the uniform distribution of GO sheets in SPES matrix. The maximum ionic conductivity has been found in 10% GO composite with higher methanol crossover resistance and selectivity. Water desalination performance of the nano-composite membranes have been evaluated by ionic flux, power consumption and current efficiency during salt removal. 10% GO nano-composite membrane shows 3.51 mol m−2 h−1 ionic flux, 4.3 kW h kg−1 power consumption and 97.4% current efficiency for salt removal. The values of ionic flux and current efficiency are 19% and 12% higher respectively while 20% lower power consumption is observed as compared to SPES membrane. The strong interfacial interactions due to the insertion of GO nanofillers into the SPES matrix improve the thermal and mechanical properties of the nanocomposite membranes. Nano-composite membrane shows the better performance and higher stability which may be used for the practical application such as DMFC and electrodialysis.

Cross-linked Hybrid Nanofiltration Membrane with Antibiofouling Properties and Self-Assembled Layered Morphology

A new siloxane monomer, 3-(3-(diethoxy(2-(5-(4-(10-ethoxy-4-hydroxy-2,2-dimethyl-11-oxa-2-ammonio-6-aza-10-silatridecan-10-yl)phenyl)-1,3,4-oxadi azol-2-ylthio)ethyl)silyl)propylamino)-2-hydroxy-N,N,N-trimethylpropan-1-aminium chloride (OA), was synthesized by reported 3-((4-(5-(2-((3-aminopropyl) diethoxysilyl)ethylthio)-1,3,4-oxadiazol-2-yl)phenyl) diethoxysilyl)propan-1-amine (APDSMO) and glycidyltrimethylammonium chloride (GDTMAC) by epoxide ring-opening reaction. OA-poly(vinyl alcohol) (PVA) hybrid antibiofouling nanofilter (NF) membranes were prepared by acid-catalyzed sol-gel followed by formal cross-linking. Membranes showed wormlike arrangement and self-assembled layered morphology with varying OA content. Hybrid NF membrane, especially OA-6, showed low surface roughness, high hydrophilic nature, low biofouling, high cross-linking density, thermal and mechanical stablility, solvent- and chlorine-tolerant nature, along with good permeability and salt rejection. Prepared OA-6 hybrid NF membrane can be used efficiently for desalting and purification of water with about 2.0 g/L salt content (groundwater in major part of India). The described method provides novel route for producing antibiofouling membranes of diversified applications.

Dramatic Improvement in Ionic Conductivity and Water Desalination Efficiency of SGO Composite Membranes

Energy efficient membranes of SGO (Sulfonated Graphene Oxide) into SPES (Sulfonated Polyethersulfone) matrix have been prepared containing different weight content of SGO. Proton conductivity and water retention capacity of membranes increases by increasing SGO while degree of swelling decreases. TEM micrograph shows the uniform distribution of SGO throughout the membrane. SGO-5 membrane shows the maximum proton conductivity (5.8 x 10−2 S/cm), which is almost double to the SPES with higher stability. SGO-5 membrane shows 4.73 mole.m−2h−1 ionic flux, 0.98 kWhkg−1 power consumption and 93.1% current-efficiency for salt removal, which are 62% and 15.2% higher, respectively, while 16% lower power consumption is observed as compared to SPES.

An environmentally friendly process for the synthesis of an fGO modified anion exchange membrane for electro-membrane applications

We report the synthesis of an anion exchange membrane (AEM) based on chemically covalently modified graphene oxide (GO) for electrodialysis and fuel cell applications. GO was modified with silica (fGO) using APTEOS which involves an epoxide ring opening reaction. The incorporation of silica particles within the GO flakes is characterized by TEM, EDX, XRD and FTIR while thermal stability is measured by TGA. Furthermore the successful development of the membrane is done by incorporating fGO within quaternized polyethyleneimine (PEI) and poly(vinyl alcohol) by a solution casting method followed by cross linking. The dispersibility of the silica modified graphene oxide is found to be very good within the polymer matrix. Membranes of various fGO content i.e. 1, 2, and 5 wt% within the PEI matrix have been synthesized. The surface morphology and structural analysis of the membranes were done using AFM, FTIR, XRD and 1H NMR. Thermo mechanical analysis of the membranes was done using TGA, DSC and UTM. Physicochemical and electrochemical analysis of the AEM were performed to quantify the ability for electro-membrane processes. The fGO-PEI-2 membrane shows excellent electrochemical properties with comparable stability among the membranes. Furthermore the applicability of AEMs has been analyzed towards electrodialysis and fuel cell application. fGO-PEI-2 membrane show great potential for electrodialysis and fuel cell application.

Highly stable acid–base complex membrane for ethanol dehydration by pervaporation separation

An investigation has been performed into the pervaporation (PV) of the water–ethanol azeotrope using sulphonated poly(ethersulphone) (SPES)–polyethyleneimine (PEI) membranes, the performance of which is compared to the SPES membrane. The SPES–PEI membranes showed high selectivity because of their alternating electrostatic deposition which yields ultrathin, water-selective polyelectrolyte membranes. The thermal and mechanical stabilities of the prepared membranes have been investigated using DSC, TGA, DMA and their structural properties by SEM. The addition of the functional group has been confirmed by solid state 13C NMR and FTIR spectroscopy. The thermal and mechanical data showed that the membranes are mechanically stable up to 250 °C. The glass transition temperature and peak sharpness increases with the quantity of the PEI component, which indicates a rise in the molecular hybridization. FTIR spectra confirm the addition of various functional groups in SPES due to the addition of PEI. The membranes containing 20% (w/w) PEI exhibited the highest water–ethanol selectivity, of the order of 4185 and a flux of 1.2 kg m−2 h−1 at 30 °C.

Synthesis of highly stable and high water retentive functionalized biopolymer-graphene oxide modified cation exchange membranes

Usage of polymer electrolyte membranes in energy based devices is substituting the conventional electrolytes. Herein, we have synthesized a PEM based biopolymer functionalized with silica modified GO and PVA. GO has been modified in two steps to synthesize silica grafted sulfonated GO. The functionalization of chitosan has been performed using 1,3-propane sultone after deacetylation. Furthermore, PVA has been used as a polymer matrix because PVA possesses good film forming property with mechanical stability. Different weight% (1, 2 and 5) of modified GO has been incorporated into the chitosan matrix. The prepared PEMs have been subjected to different types of characterization such as structural, thermal, mechanical and electrochemical characterization. The nano-hybrid membranes show significant increment in electrochemical properties. MGO–SCH-5 membrane shows a proton conductivity of 6.77 × 10−2 S cm−1, which increases to 11.2 × 10−2 S cm−1 at 90 °C. The thermal and mechanical stability of PEM also increases with MGO content in the sulfonated chitosan. The elastic modulus for the MGO–SCH-5 membrane is calculated to be 21.37 MPa with 54 MPa of maximum stress. Thus, these membranes may be targeted as PEMs for higher temperature energy applications.

Enhanced Electrochemical Performance of Stable SPES/SPANI Composite Polymer Electrolyte Membranes by Enriched Ionic Nanochannels

Herein, we present the results of sulfonated polyaniline (SPANI) and sulfonated poly(ether sulfone) (SPES) composite polymer electrolyte membranes. The membranes are established for high-temperature proton conductivity and methanol permeability to render their applicability. Composite membranes have been prepared by modifying the SPES matrix with different concentrations of SPANI (e.g., 1, 2, 5, 10, and 20 wt %). Structural and thermomechanical characterizations have been performed using the transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analyzer techniques. Physicochemical and electrochemical properties have been evaluated by water uptake, ion-exchange capacity, dimensional stability, and proton conductivity. Methanol permeability experiment was carried out to analyze the compatibility of prepared membranes toward direct methanol fuel cell application and found the lowest methanol permeability for PAS-5. Also, the membranes reveal excellent thermal, mechanical, and physicochemical properties for their application toward high-temperature electromembrane processes.

Amide functionalized MWNT/SPEEK composite membrane for better electrochemical performance

Nanocomposite membranes based on multiwalled carbon nanotube /SPEEK (sulfonated poly ether ether ketone) have been synthesized via simple solution casting. Prior to use CNT have been purified and grafted with carboxylic acid groups onto its walls by means of sulfuric and nitric acid. Afterwards, amidation of carboxylated CNTs (c-CNT) has been done. Amidated CNT (a-CNT) is then incorporated in SPEEK polymer matrix to synthesize nanocomposite membranes. Physicochemical, structural, thermal and mechanical characterizations are done through the respective techniques. Electric and ionic conductivities have also been evaluated. Composites membranes show the enhanced electrochemical performance with higher electric conductivity.