Kusumastuti, Ella (2026) Pengembangan Membran Polimer Elektrolit Berbasis Kitosan dengan Filler Sulfur-Modified Graphene-Magnetite melalui Fabrikasi Berbantuan Medan Magnet. Doctoral thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Membran polimer elektrolit berbasis kitosan merupakan salah satu kandidat material ramah lingkungan yang berpotensi menggantikan membran komersial, namun masih menghadapi kendala berupa konduktivitas proton yang relatif rendah, permeabilitas metanol yang tinggi, serta stabilitas fisikokimia yang belum optimal. Penelitian ini bertujuan untuk mengembangkan membran polimer elektrolit berbasis kitosan dengan filler sulfur-modified graphene–magnetite (SGM) melalui fabrikasi berbantuan medan magnet eksternal untuk meningkatkan karakteristik struktur, sifat fisikokimia, dan kinerja membran. Sulfur-modified graphene (SG) disintesis melalui modifikasi permukaan grafit menggunakan asam sulfat pekat dan dikonjugasikan dengan magnetit (Fe3O4) menggunakan metode kopresipitasi. Filler yang dihasilkan dikarakterisasi menggunakan X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDX), Particle Size Analysis (PSA), dan pengukuran suseptibilitas magnet untuk mengevaluasi struktur kristal, gugus fungsi, cacat struktur, komposisi kimia permukaan, morfologi dan distribusi ukuran partikel, serta sifat kemagnetannya. Selanjutnya, filler didispersikan ke dalam matriks kitosan dan membran difabrikasi di bawah pengaruh medan magnet lemah 0,02 Tesla guna meningkatkan orientasi dan distribusi filler di dalam matriks polimer. Membran komposit yang dihasilkan dikarakterisasi berdasarkan struktur, kapasitas pertukaran ion, penyerapan air dan metanol, stabilitas termal, ketahanan oksidatif, sifat mekanik, konduktivitas proton, dan permeabilitas metanol. Hasil karakterisasi filler menunjukkan bahwa modifikasi sulfur berhasil mengubah karakteristik permukaan graphene, sedangkan konjugasi dengan magnetit menghasilkan filler dengan sifat kemagnetan yang mendukung orientasi di bawah medan magnet. Evaluasi terhadap membran komposit menunjukkan bahwa performa membran tidak hanya dipengaruhi oleh karakteristik filler, tetapi juga oleh interaksi filler–matriks serta orientasi filler selama proses fabrikasi. Di antara seluruh membran yang dikembangkan, membran Chitosan/graphene–magnetite yang difabrikasi berbantuan medan magnet (Chi/GEMF) menunjukkan kinerja terbaik dengan konduktivitas proton sebesar 32,14 mS/cm (25oC), permeabilitas metanol sebesar 6,65 × 10-6 cm2/s, dan selektivitas sebesar 4,83 × 106 mS s cm-3, yang menunjukkan keseimbangan optimum antara kemampuan transport proton dan sifat penghalang metanol dibandingkan membran lainnya. Temuan ini menunjukkan bahwa sinergi antara modifikasi permukaan graphene, konjugasi magnetit, dan fabrikasi berbantuan medan magnet merupakan strategi yang efektif dalam pengembangan membran polimer elektrolit berbasis kitosan berkinerja tinggi.
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Chitosan-based polymer electrolyte membranes have attracted considerable attention as environmentally friendly alternatives to commercial polymer electrolyte membranes. However, their practical application is still limited by relatively low proton conductivity, high methanol permeability, and inadequate physicochemical stability. This study aimed to develop chitosan-based polymer electrolyte membranes incorporating sulfur-modified graphene–magnetite (SGM) filler through magnetic field-assisted fabrication to improve their structural characteristics, physicochemical properties, and membrane performance. Sulfur-modified graphene was synthesized via the surface modification of graphite using concentrated sulfuric acid, followed by conjugation with magnetite (Fe3O4) through a co-precipitation method. The synthesized filler was characterized using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDX), Particle Size Analysis (PSA), and magnetic susceptibility measurements to evaluate its crystal structure, functional groups, structural defects, surface chemical composition, morphology, particle size distribution, and magnetic properties. Subsequently, the filler was dispersed into a chitosan matrix, and the composite membranes were fabricated under an external magnetic field (0.02 Tesla) to promote filler orientation and homogeneous distribution within the polymer matrix. The resulting membranes were characterized in terms of structural properties, ion exchange capacity, water and methanol uptake, thermal stability, oxidative stability, mechanical properties, proton conductivity, and methanol permeability. The filler characterization confirmed that sulfur modification successfully altered the surface characteristics of graphene, while conjugation with magnetite produced a magnetic filler capable of responding to an external magnetic field. Evaluation of the composite membranes demonstrated that membrane performance was governed not only by the intrinsic characteristics of the filler but also by filler–matrix interactions and filler orientation during the fabrication process. Among all developed membranes, the magnetic field-assisted chitosan/graphene–magnetite membrane (Chi/GEMF) exhibited the best overall performance, achieving a proton conductivity of 32.14 mS cm-1 at 25 °C, a methanol permeability of 6.65 × 10-6 cm2 s-1, and a selectivity of 4.83 × 106 mS s cm-3, indicating an optimal balance between proton transport capability and methanol barrier properties. These findings demonstrate that the synergistic effects of graphene surface modification, magnetite conjugation, and magnetic field-assisted fabrication constitute an effective strategy for developing high-performance chitosan-based polymer electrolyte membranes.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Uncontrolled Keywords: | fabrikasi berbantuan medan magnet, matriks kitosan, membran polimer elektrolit, sulfur-modified graphene–magnetite, Direct Methanol Fuel Cell (DMFC), magnetic field-assisted fabrication, chitosan matrix, electrolyte polymer membrane, sulfur-modified graphene–magnetite, Direct Methanol Fuel Cell (DMFC) |
| Subjects: | Q Science > QD Chemistry > QD341.H9 Graphene |
| Divisions: | Faculty of Science and Data Analytics (SCIENTICS) > Chemistry > 47001-(S3) PhD Thesis |
| Depositing User: | Ella Kusumastuti |
| Date Deposited: | 14 Aug 2026 08:48 |
| Last Modified: | 14 Aug 2026 08:48 |
| URI: | http://repository.its.ac.id/id/eprint/144352 |
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