Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Kimya Bölümü, Türkiye
Tezin Onay Tarihi: 2015
Öğrenci: SEVDA SELİME KALYONCU
Danışman: GÜLSÜN GÖKAĞAÇ ARSLAN
Özet:In this thesis, carbon supported platinum catalysts were synthesized to investigate the effect of reducing agent and surfactant on the performance of catalyst towards methanol oxidation reaction. For this purpose, the catalysts were prepared by using PtCl4 as a starting material, propylamine (a) and dipropylamine (b) as surfactant, and sodium borohydride (catalyst I) and formaldehyde (catalyst II) as reducing agent. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, cyclic voltammetry (CV) and chronoamperometry (CA). XRD and TEM results indicated that platinum has face-centered cubic (fcc) structure and it consists of small (~5nm) and agglomerated (30-70 nm for catalyst I, 40-120 nm for catalyst II) particles and they were homogeneously dispersed on carbon support. The results also revealed that the morphology of the platinum particles depends on the kind of reducing agent, for instance; they have cubic and formless shape when sodium borohydride and formaldehyde were used, respectively. The Pt 4f region of XP spectra showed that platinum has two different oxidation states, Pt(0) and Pt(IV), and it composed of 61-67 % Pt (0) and 39-33 % Pt(IV). VI Oxygen 1s and carbon 1s peaks displayed that there are COads, OHads, H2Oads, (C=C)ads, (C-O)ads, (C=O)ads and (COO-)ads on the surface of catalyst. BET analysis revealed that the surface areas of the catalyst Ia-b and IIa-b before adding carbon support were ~49 m2/g sample and ~32 m2/g sample, respectively. Electrochemical studies indicated that; a) The performance of catalysts depends on the kind of surfactants and reducing agents. b) Catalyst Ia has the best performance towards methanol oxidation reaction, because it has highest electrochemical surface area, percent platinum utility and roughness factor. c) The performance of catalyst Ia (~240 mA/mg Pt) is ~3 times larger than commercial E-TEK catalyst (~75 mA/mg Pt).