Thesis Type: Postgraduate
Institution Of The Thesis: Recep Tayyip Erdogan University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2017
Thesis Language: Turkish
Student: MEHMET AKİF AZDER
Principal Supervisor (For Co-Supervisor Theses): Mehmet Şahin
Co-Supervisor: Mehmet Suha YazıcıAbstract:
n this study, Oxygen Reduction Reaction (ORR) activity and usability of nitrogen-doped multilayer graphene as electrocatalyst in Proton Exchange Membrane (PEM) fuel cells were researched. First, single-layer, few-layer and multi-layer graphene produced with Chemical Vapor Deposition (CVD) technique. Different gas flow rates, temperatures, growth times and, different substrates were tried for production of graphene. Transfer of graphene from the substrate that was produced on to different substrates was studied. Graphene was doped with ammonia under different temperatures and different times. Surfaces of the graphene and N-doped graphene samples were observed with Scanning Electron Microscope (SEM). Raman Spectroscopy was utilized to characterize samples produced. Doping amounts and doping structures of graphene samples were characterized with X-ray Photoelectron Spectroscopy (XPS). ORR activity of doped and non-doped graphene samples were tested with Rotating Disk Electrode (RDE) technique and finally transferred to a single-cell PEM fuel cell for performance measurements. Results of nitrogen-doped graphene samples compared with the commercially available platinum catalyst. RDE studies showed that ORR activities rose with more doping. Doped graphene samples have provided current up to 60 µA while non-doped graphene has provided only 3-4 µA. Levich study showed that the number of electron transferred with doped graphene samples were close to each other (n=0,079 and n=0,105) but less than electrodes containing platinum catalyst (n=3,95). Finally, in fuel cell test, doped graphene samples with 5 cm2 surface area and 0,5V polarization gave about 0,6 mA on cathode side and 2 mA on anode side while the electrodes with non-doped graphene did not give any current at all.