Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Preparation and Characterization of Novel Catalysts to be Used in Direct Methanol Fuel Cells

Fuel cell is a system which converts chemical energy to electrical energy from an oxidation-reduction reaction of methanol and oxygen.

In this study, PtCo/C, PtNi/C, PtV/C and PtCoNi/C catalysts were prepared by polyol method and hydrazine reduction of metal precursors to use on anode side of direct methanol fuel cells.

The electrochemical performance of the catalysts for the methanol electrooxidation in acidic media at room temperature is evaluated and compared with that of a Pt/C catalyst. Electrochemical measurements were carried out by using cyclic voltammetry, lineer sweep voltammetry and choronoamperometry. PtNi/C catalyst which was prepared by hydrazine reduction and PtCo/C catalyst which was prepared by polyol method with using 1,2 propandiol showed much higher catalytic activity towards methanol oxidation in anodic reactions.

The structure and morphology of the catalysts were analyzed using X-Ray diffractometer. All XRD patterns show the four main characteristic peaks of the face-centered cubic (fcc) cristalline structure of Pt, namely the planes (1 1 1), (2 0 0), (2 2 0) and (3 1 1). No peaks for pure cobalt, nickel, vanadium and its oxides were found, but their presence can not be discarded because they may be present in very small amount or even in an amorphous form.

Gas diffusion layers were composed by using as-prepared four electrocatalysts for anode side and commercial Pt/C catalyst was used for cathode side of fuel cell. Catalyst layer surfaces were analyzed by scanning electron microscopy (SEM) and we understood by EDS analysis that catalysts were spread uniformly on a carbon paper. Compared with SEM images of literature and this study, similar images were obtained.

Membran electrode assembly were composed by prepared-gas diffusion layers for anode and cathode and they were analyzed by DMFC test unit. MEA with PtNi/C H1-E.G catalyst for anode side reached much higher current density and maximum power.