1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Fuel Cell Institute / Institut Sel Fuel

Title:	Membran nanokomposit nafion/SiO₂-Pd untuk aplikasi sel fuel metanol langsung
Authors:	Thiam Hui San (P54770)
Supervisor:	Wan Ramli Wan Daud, Prof. Ir. Dr. Hj.
Keywords:	Sel fuel metanol Direct methanol fuel cells
Issue Date:	4-Apr-2014
Description:	Sel fuel metanol langsung (DMFC) mempunyai potensi tinggi sebagai sumber penjanaan tenaga bersih untuk aplikasi teknologi elektronik mudah alir. Walaubagaimanapun, pengkomersialan teknologi DMFC masih terbatas oleh kinetik anod yang lembap, lintasan metanol, pemangkin elektrod berasaskan platinum yang mahal, serta masalah pengurusan reaktan dan produk tindak balas. Lintasan metanol adalah salah satu isu yang penting dalam DMFC yang sering menyebabkan pembaziran metanol yang tinggi, kesan potensi bercampur dan keracunan mangkin yang menjejaskan prestasi sel secara serius. Oleh itu, kajian penyelidikan ini memberi tumpuan kepada pembangunan membran komposit bernanostruktur yang mempamerkan kebolehtelapan metanol rendah dan kekonduksian proton tinggi untuk meningkatkan prestasi DMFC. Nanokomposit tidak organik gentian SiO2-Pd dipilih sebagai bahan tambahan untuk dimasukkan ke dalam Nafion melalui kaedah tebaran pelarut. Kepekatan kumpulan silanol yang tinggi pada struktur nanogentian komposit, sifat higroskopi silika, sifat pemangkinan paladium dan kestabilan mekanik gentian membantu meningkatkan lagi kepilihan membran. Dalam kajian ini, kesan kandungan gentian, suhu penyepuhlindapan dan pelarut tebaran terhadap sifat elektrokimia dan pengangkutan membran telah dikaji menggunakan kaedah Taguchi. Pelbagai kaedah ujikaji dan teknik pencirian konvensional telah digunakan untuk mengkaji sifat membran nanokomposit. Ujian prestasi himpunan membranelektrod (MEA) dilakukan dengan membran nanokomposit sebagai elektrolit dalam DMFC tunggal pasif pada suhu bilik. Membran komposit yang disediakan dengan pelarut dimetil sulfoksida (DMSO), berat gentian 3 % dan disepuhlindapan pada suhu 160 oC memaparkan prestasi paling tinggi dengan kekonduksian proton 0.092 Scm-1 dan lintasan metanol terendah iaitu 5.83 x 10-7 cm2s-1. Struktur membran nanokomposit yang padat dapat mengurangkan lintasan metanol secara fizikal dan kimia, di samping mengekalkan kekonduksian proton yang tinggi setahap membran Nafion. Kadar penyerapan air dan kestabilan terma membran komposit dipertingkatkan juga. Hasil analisis struktur kumpulan berfungsi kimia menunjukkan bahawa ikatan terbentuk antara kumpulan silanol dan sulfonik Nafion, ini memberikan keserasian yang baik antara gentian komposit dan matriks Nafion. Analisis morfologi membran menunjukkan bahawa satu sub-lapisan gentian terbentuk pada permukaan Nafion tanpa retakan yang signifikan dan penyerakan gentian yang homogen dalam matriks Nafion diperolehi. Selektiviti membran nanokomposit Nafion/SiO2-Pd adalah lebih tinggi 53 % daripada Nafion 117 komersial. Ketumpatan kuasa dan voltan litar terbuka (OCV) membran nanokomposit (10.9 mWcm- 2; 0.64 V) menunjukkan peningkatan ketara berbanding dengan membran Nafion 117 komersial yang lebih tebal (7.95 mWcm-2; 0.60 V), di mana peningkatan sebanyak ~37% dalam ketumpatan kuasa dapat diperolehi. Di samping itu, simulasi dinamik molekul membran nanokomposit menggunakan anjakan min persegi dan fungsi taburan jejarian digunakan bagi meramal interaksi dan resapan molekul dalam sistem membran tersimulasi. Hasil simulasi dapat disahkan dengan baik oleh data eksperimen. Keputusan kedua-dua kajian teori dan eksperimen mengesahkan potensi besar membran komposit Nafion/SiO2-Pd dalam aplikasi DMFC.,Direct methanol fuel cells (DMFCs) have great potential as a source of clean power generation for application in portable electronic technologies. However, commercialization of passive DMFC technology is still limited by sluggish anode kinetics, methanol crossover, costly platinum based electrode catalyst, reactant and product management. Methanol crossover is one of the key issues in DMFC, which always leads to high wastage of fuel, mixed potential effects and catalyst poisoning that affects seriously on cell performance. The present research work is thus focused on the development of nanocomposite membranes that have low methanol permeability and high proton conductivity, which would improve DMFC performance. Composite inorganic Pd-SiO2 nanofiber was adopted as additive to incorporate within the host Nafion via solvent casting technique. The high concentration of silanol groups in the composite nanofiber structure, the hygroscopic nature of silica, the catalytic properties of palladium and the mechanical stability of the nanofiber help to improve membrane selectivity. In this study, the effect of fiber loading, annealing temperature and casting solvent on membrane electrochemical and transport properties were investigated by using Taguchi method. Various conventional experiments and characterization techniques were employed to characterize the nanocomposite membranes. Performance tests of membrane electrode assembly (MEA) with the nanocomposite membranes were evaluated using a passive single cell DMFC at room temperature. The dimethyl sulfoxide (DMSO)-casted nanocomposite membrane with 3 wt% fiber loading, and annealed at 160 oC, exhibits the highest performance with proton conductivity of 0.092 Scm-1 and the lowest methanol crossover of 5.83 x 10-7 cm2s-1. The more compact structure of the composite membrane may have physically and chemically alleviated the methanol crossover problem while maintaining a high level of conductivity comparable to those of commercial Nafion membranes. The water uptake and thermal stability of the composite membrane improve as well. The results of chemical functional group analysis indicate that bonding formed between the silanol and sulfonic groups of Nafion which provide a good compatibility between the composite fiber and Nafion matrix. Morphology analysis showed that a fiber sublayer formed on Nafion without significant cracking and homogeneous dispersion of fiber within Nafion matrix is obtained. Selectivity of nanocomposite membrane Nafion/SiO2-Pd is 53 % higher than that commercial Nafion 117. The power density and open circuit voltage (OCV) of the nanocomposite membrane (10.9 mWcm-2, 0.64 V) were significantly improved compared to those of the much thicker commercial Nafion 117 (7.95 mWcm-2; 0.60 V) where improvement around 37 % in power density is achieved. In addition, molecular dynamics simulation of the nanocomposite membrane using mean square displacement and radial distribution functions were used to predict the molecular interaction and diffusion in the simulated membrane system. The simulation results were found to be well validated by experimental data. Both theoretical and experimental investigations have shown the great potential of nanocomposite membranes Nafion/SiO2-Pd in DMFC application.,PhD
Pages:	174
Call Number:	TK2933.D57T488 2014 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Fuel Cell Institute / Institut Sel Fuel

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.