Investigating the usefulness of chitosan based proton exchange membranes tailored with exfoliated molybdenum disulfide nanosheets for clean energy applications.

Chitosan based proton exchange membranes (PEMs) has been synthesized by a facile solution casting strategy using two-dimensional exfoliated molybdenum disulfide (E-MoS2) nanosheets. The prepared PEMs are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field-emission scanning electron microscopy (FESEM) with Energy dispersive X-ray spectroscopy (EDX), water uptake, Thermogravimetric analysis (TGA), AC impedance spectroscopy and cyclic voltammetry. In comparison with pure chitosan membrane, E-MoS2 nanosheets incorporated membranes exhibit excellent water absorbing capacity, ion-exchange capacity and proton conductivity. Moreover, the changes in roughness of nanocomposite membranes is investigated by atomic force microscopy (AFM) and the results confirm that the E-MoS2 nanosheets content enhances the surface roughness as well as provide good mechanical and thermal resistivity to the chitosan/E-MoS2 membranes. Chitosan membranes with 0.75% E-MoS2 nanosheets demonstrated higher proton conductivity of 2.92 × 10-3 Scm-1 and membrane selectivity of 8.9 × 104 Scm-3 s with reduced methanol permeability of 3.28 × 10-8 cm2 s-1. Overall, results evidenced that the chitosan/E-MoS2 nanocomposite membranes will be an alternate to Nafion in direct methanol fuel cells (DMFCs).

Custom-made PEI/exfoliated-MoS2 nanocomposite ultrafiltration membranes for separation of bovine serum albumin and humic acid.

Herein, we report the effect of the exfoliated molybdenum disulfide (eMoS2) nanosheets in improving the permeability and anti-fouling properties of the PEI ultra-filtration (UF) membrane using bovine serum albumin (BSA) and humic acid (HA) as model fouling agents. The PEI/eMoS2 nanocomposite membranes were prepared via phase inversion method using three different eMoS2 concentrations (0.5, 1 and 2wt%) designated as PEI-0.5, PEI-1 and PEI-2, respectively. Fourier transform infra-red spectroscopy employed to probe the surface functionalities on the membranes. Contact angle measurement, pure water flux, swelling rate and solute rejection studies confirmed the improved hydrophilicity of the PEI/eMoS2 nanocomposite membranes than the individual entities. Flux recovery ratio (FRR), reversible and irreversible fouling results evidenced the improved fouling resistance of PEI/eMoS2 modified membranes than the individual counterparts. SEM results evidenced that the nanoscale eMoS2 significantly altered the membrane morphology by causing increased porosity and larger macrovoids formation on the surface as well as in the bulk of the membrane. PEI-1 membrane showed an increased pure water flux (52.54Lm-2h-1) and water content (74.8%) whereas lesser contact angle (69.2°) and hydraulic resistance (1.85kPa/Lm-2h-1). Resistance to fouling performance of PEI-1 membrane was evident from the FRR values of 95.3 and 90.2% and rejection values of 94.5 and 92.4% for BSA and HA respectively. PEI-2 membrane agglomerates with eMoS2 and hindered the membrane permeability by blocking the macrovoids in the bulk which restricted the permeation and fouling resistance of the membrane. Amongst various nanocomposite membranes investigated, the PEI-1 membrane exhibited better hydrophilicity and fouling resistance properties due to the availability of the favorable surface and bulk characteristics.