Amit K. Thakur

Sulfonated polyimide/acid-functionalized graphene oxide composite polymer electrolyte membranes with improved proton conductivity and water-retention properties.

Sulfonated polyimide (SPI)/sulfonated propylsilane graphene oxide (SPSGO) was assessed to be a promising candidate for polymer electrolyte membranes (PEMs). Incorporation of multifunctionalized (-SO3H and -COOH) SPSGO in SPI matrix improved proton conductivity and thermal, mechanical, and chemical stabilities along with bound water content responsible for slow dehydration of the membrane matrix. The reported SPSGO/SPI composite PEM was designed to promote internal self-humidification, responsible for water-retention properties, and to promote proton conduction, due to the presence of different acidic functional groups. Strong hydrogen bonding between multifunctional groups thus led to the presence of interconnected hydrophobic graphene sheets and organic polymer chains, which provides hydrophobic-hydrophilic phase separation and suitable architecture of proton-conducting channels. In single-cell direct methanol fuel cell tests, SPI/SPSGO-8 exhibited 75.06 mW·cm(-2) maximum power density (in comparison with commercial Nafion 117 membrane, 62.40 mW·cm(-2)) under 2 M methanol fuel at 70 °C.

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.

Controlled metal loading on poly(2-acrylamido-2-methyl-propane-sulfonic acid) membranes by an ion-exchange process to improve electrodialytic separation performance for mono-/bi-valent ions

Highly cross-linked poly(2-acrylamido-2-methyl-propane-sulfonic acid) (PMPS) based cation-exchange membranes (CEMs) were prepared and the mono-valent selectivity of the membranes was significantly improved using the pore-sieving strategy by metal (copper) loading by the ion-exchange process. The prepared membranes were characterized for their morphological, physicochemical, electrochemical, and electrodialytic properties. Metal (Cu) loading in the PMPS membrane matrix improved thermal, mechanical, oxidative and hydrolytic stabilities. The results demonstrated that fine control over membrane permselectivity is possible and can be effectively tuned. Metal modification on the CEM surface improved the blocking behaviour and restricted the transport (leakage) of bi-valent metal cations (Ni2+ and Zn2+) during electrodialytic separation of mono- and bi-valent ions. However, partial deterioration in membrane ionic conductivity showed a slight adverse effect on the electrodialytic performance of the modified membranes. Extremely low Zn2+ leakage for the prepared PMPS-3 membrane in comparison with other state-of-the-art CEMs was attributed to the excellent pore-size sieving effect. The metal loaded PMPS-3 membrane showed improved surface compactness, which hindered the easy accessibility of bulky counter-ions (Ni2+/Zn2+) to fixed charge and thus quite low transport (leakage) of bi-valent ions was observed.

A poly(vinylidene fluoride-co-hexafluoro propylene) nanohybrid membrane using swift heavy ion irradiation for fuel cell applications

Through channels in thin polymer/nanohybrid films have been made by irradiating with high energy swift heavy ions (SHI) followed by selective chemical etching of the amorphous zone in the latent track created by SHI during the bombardment. The average size of the nanochannels (30–65 nm) was controlled by varying the fluence of SHI along with the nanohybrid preparation of the polymer, by dispersing a few percent of two-dimensional nanoclay in the matrix. Grafting was applied within the nanochannels through polymerization of conducting poly(3-hexyl thiophene) which was further functionalized to make the channels ion conducting. Nanoclay alters the crystalline phase to the piezoelectric all-trans β-phase in the nanohybrid whose extent has increased further after irradiation, grafting and sulphonation. Structural alteration has also been reflected in its thermal behavior (similar melting behavior in the pure polymer against the considerably higher melting point in the functionalized nanohybrid). The bulk dc conductivity of the functionalized membrane increased 13 orders of magnitude compared to the unirradiated specimens and activation energies also increased for the functionalized hybrid membrane (20 and 32 kJ mol−1 for the functionalized pure polymer and its nanohybrid, respectively) suggesting better stability of the functionalized membranes at higher temperature. Water uptake and proton conductivities of the functionalized hybrid membranes are similar to those of the standard Nafion membrane while the higher selectivity parameter along with significantly lower methanol permeability of the functionalized hybrid membrane strongly suggests that it is a better membrane for fuel cell applications. A membrane electrode assembly has been prepared to measure the performance of direct methanol fuel cells indicating a significantly higher value of power density of the developed functionalized hybrid membranes.

Phosphorylated cellulose triacetate–silica composite adsorbent for recovery of heavy metal ion

Phosphorylated cellulose triacetate (CTA)/silica composite adsorbent was prepared by acid catalyzed sol-gel method using an inorganic precursor (3-aminopropyl triethoxysilane (APTEOS)). Reported composite adsorbent showed comparatively high adsorption capacity for Ni(II) in compare with different heavy metal ions (Cu(2+), Ni(2+), Cd(2+) and Pb(2+)). For Ni(II) adsorption, effect of time, temperature, pH, adsorbent dose and adsorbate concentration were investigated; different kinetic models were also evaluated. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were also estimated and equilibrium adsorption obeyed Langmuir and Freundlich isotherms. Developed adsorbent exhibited about 78.8% Ni(II) adsorption at pH: 6 and a suitable candidate for the removal of Ni(II) ions from wastewater. Further, about 65.5% recovery of adsorbed Ni(II) using EDTA solution was demonstrated, which suggested effective recycling of the functionalized beads would enable it to be used in the treatment of contaminated water in industry.

Synthesis and characterization of TiO2and Ag/TiO2nanostructure

Single phase anatase TiO 2 nanoparticles were prepared using Titanium tertachloride ( TiCl 4 ) as precursor through an inexpensive method. Well dispersed nanocomposites of silver at TiO 2 were synthesized successfully by photochemical route. Both TiO 2 and Ag / TiO 2 were characterized using X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). The particle size of TiO 2 is found to be ∼ 11 nm and ∼ 22 nm for Ag / TiO 2 , by XRD and confirmed by TEM. TEM micrographs also show the single phase crystal of TiO 2 and confirm the deposition of silver among TiO 2 .

Synthesis and characterization of TiO[sub 2] and Ag∕TiO[sub 2] nanostructure

Single phase anatase TiO 2 nanoparticles were prepared using Titanium tertachloride ( TiCl 4 ) as precursor through an inexpensive method. Well dispersed nanocomposites of silver at TiO 2 were synthesized successfully by photochemical route. Both TiO 2 and Ag / TiO 2 were characterized using X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). The particle size of TiO 2 is found to be ∼ 11 nm and ∼ 22 nm for Ag / TiO 2 , by XRD and confirmed by TEM. TEM micrographs also show the single phase crystal of TiO 2 and confirm the deposition of silver among TiO 2 .

Synthesis and characterization of TiO2 and Ag/TiO2 nanostructure

Single phase anatase TiO 2 nanoparticles were prepared using Titanium tertachloride ( TiCl 4 ) as precursor through an inexpensive method. Well dispersed nanocomposites of silver at TiO 2 were synthesized successfully by photochemical route. Both TiO 2 and Ag / TiO 2 were characterized using X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). The particle size of TiO 2 is found to be ∼ 11 nm and ∼ 22 nm for Ag / TiO 2 , by XRD and confirmed by TEM. TEM micrographs also show the single phase crystal of TiO 2 and confirm the deposition of silver among TiO 2 .