Lukman Atmaja

Biopolymer-based electrolyte membranes from chitosan incorporated with montmorillonite-crosslinked GPTMS for direct methanol fuel cells

A composite membrane was fabricated from biopolymer chitosan and montmorillonite (MMT) filler as an alternative membrane electrolyte for direct methanol fuel cell (DMFC) application. To first improve the organic–inorganic interfacial morphology, the pristine MMT was pre-treated using 3-glicidoxy propyltrimethoxysilane (GPTMS) surface modifier to produce organophilic MMT (O-MMT). The GPTMS modified MMT was mixed with chitosan in acetic acid solution and cast into membranes. SEM images and FTIR analysis showed that the O-MMT was successfully incorporated into the chitosan polymer matrix. Water and methanol uptake of the Ch/O-MMT composite membranes decreased with increasing O-MMT loadings, but the ion exchange capacity (IEC) value increased. The Ch/O-MMT with 5 wt% O-MMT loading exhibited the best methanol permeability and proton conductivity characteristics among the other Ch/O-MMT membranes, which were 3.03 × 10−7 cm2 s−1 and 4.66 mS cm−1, respectively. All the results obtained from this study can be used to conclude that the chitosan membrane with O-MMT filler is a promising high performance PEM candidate for DMFC application.

Hubungan antara kekonduksian proton, sifat hidrofil dan kestabilan termal atas membran komposit kitosan/montmorillonit dengan modifikasi GPTMS dan prestasinya dalam sel bahan api metanol langsung

Chitosan based inorganic hybrid membrane is a promising organic–inorganic hybrids for the development of high performance proton exchange membrane (PEM). The immobilization of modified montmorillonite (MMT) using GPTMS within chitosan matrix would possess superior physicochemical characteristics due to more hydrogen bonding formation introduced by GPTMS. Therefore, higher number hydrogen bond formation can be expected in Ch/MMT-GPTMS membrane rather than in pure Ch membrane. A fully hydrated membrane at elevated temperatures is desirable for efficient proton conduction in the membranes. It remains a critical challenge to maintain proper hydration of the membranes for the operation of the direct methanol fuel cell (DMFC). The microstructure obtained by SEM for composites showed that filler was successfully incorporated and relatively well dispersed in the chitosan polymer matrix. The role of surface modification of MMT filler by GPTMS have increase the functional group that can form hydrogen bonding which suitable for interaction with water. High water uptake is favourable for high performance PEM to facilitate great numbers of protons hopping and diffusion through the membrane. In addition, greater hydrogen bonding formation would lead to the tighter packing of composite membrane, resulting in higher bonding strength and higher thermal resistance. The Ch/MMT-GPTMS composite membrane with 5 wt% filler loading exhibited the best proton conductivity are 4.66 mScm-1, with water contact angle value of 64.73°. A maximum power density of 0.24 mWcm-2 was obtained with a 2M methanol feed. The relationship of water contact angle, water upake, membrane swelling, thermal stability, and proton conductivity shown suitable trend, it means that all quality of them are related to the hydrophilicity properties.

Modification of chitosan membranes with nanosilica particles as polymer electrolyte membranes

Chitosan has been widely used as polymer matrix for Polymer Electrolyte Membrane (PEM) application replacing Nafion which has shortcomings in terms of high methanol permeability that degrades the performance of fuel cells. Chitosan membranes modification is performed by adding nanosilica to prevent methanol transport through the membrane. Nanosilica is synthesized by sol-gel method and the particle diameter is obtained by analysis using Breunner Emmet Teller (BET) that is 6.59 nm. Nanosilica is mixed with chitosan solution to obtain nanosilica-chitosan as polymer electrolyte membrane. The membranes are synthesized through phase inversion method with nanosilica composition including 0; 0.5; 1; 2; 3; 5; and 10% w/w of chitosan. Characterization of the membranes indicate that the results of water swelling, proton conductivity and methanol permeability of the membrane with 3% nanosilica respectively were 49.23%, 0.231 S/cm, and 5.43 x 10−7 cm2/s. Based on the results of membrane selectivity calculation, the o...