Date

2015

Author

Çokangın, Aysu

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In this thesis, carbon supported platinum nanoparticle catalysts were synthesized by using PtCl4 as precursor, sodium borohydride (Cat I), hydrazinum hydroxide (Cat II) and formaldehyde (Cat III) as reducing agent and 1-heptanamine (a), Nmethylheptanamine (b) and N,N-dimethylheptanamine (c) as surfactants for methanol oxidation reaction. Their physical and electrochemical properties were determined by inductively coupled plasma spectroscopy (ICP), cyclic voltammetry (CV), and characterization methods of X-ray diffraction (XRD), X-photoelectron Spectroscopy (XPS), transmission electron microscopy (TEM) and Brunauer, Emmnett and Teller (BET) surface area analysis. XRD and TEM results indicated that all catalysts exhibit face centered cubic structure and contain small and agglomerated platinum particles in different shape, size, ratio and density. Cat I composed of small (~ 5 nm) and significant number of quite dense spherical agglomerated (~ 20 - ~ 150 nm) particles, Cat II comprises small (~ 5 nm) cubic and formless agglomerated (~ 20 - ~ 300 nm) particles and Cat vi III contains large number of small (~ 5 nm) and a few number of spherical, less dense and agglomerated (~ 20 - ~ 200 nm) particles. XPS data displayed that platinum exist in two different oxidation states, Pt(0) (~64.5~69.6 %) and Pt(IV) (~35.5-~30.4 %) and platinum surface includes adsorbed OH, H2O, C-O, C=O, C-OH, partially crystalline carbon and/or hydrocarbon. BET analysis showed that the surface area of the Cat Ia, IIa, IIIa, Ib, IIb, IIIb, Ic, IIc and IIIc are 27.58, 27.88, 36.25, 5.44, 6.27, 6.22, 26.80, 32.50 and 52.88 m2/ g Pt respectively. The highest surface area recorded to catalyst IIIc. These results illustrated that surface area of the catalyst depends on the reducing agent that was used. However no trace was found to indicate the surfactant effect on the surface area of catalysts. Electrochemical studies revealed that the order of performance of catalysts towards methanol oxidation reaction is Catt II < Cat I < Cat III and Cat IIIc has the highest performance, which is 2.23 times larger than E-TEK catalyst. It was found that the performance of catalysts depends on the kind of surfactant and reducing agent, electrochemical surface area, percent platinum utility, roughness factor, and If / Ir ratio.

Subject Keywords

Methanol as fuel., Methanol, Platinum., Catalysts., Nanoparticles.

URI

http://etd.lib.metu.edu.tr/upload/12618720/index.pdf
https://hdl.handle.net/11511/24623

Collections

Graduate School of Natural and Applied Sciences, Thesis