Platinum nanoparticles supported with graphene nanoplatelets and hybrid carbon materials designed as electrocatalysts for PEM fuel cells
Arıcı, Ece (2018) Platinum nanoparticles supported with graphene nanoplatelets and hybrid carbon materials designed as electrocatalysts for PEM fuel cells. [Thesis]
Polymer Electrolyte Membrane Fuel Cell (PEMFC) is one of the most promising electrochemical conversion devices thanks to its environmental friendly structure, high power density and scalability. These properties of PEMFC let its development in the recent years and many efforts are towards increasing its efficiency nowadays. The major drawback for the commercialization of PEMFC is the corrosion in Membrane Electrode Assembly (MEA) unit which is the heart of the PEMFC in terms of cost and efficiency. Therefore, it is vital to lower its cost by increasing the performance of the electrodes while decreasing the degradation in the MEA. Platinum (Pt) is generally used as the catalyst embedded on a proper carbon support due to its unique properties for the electrochemical reactions to occur on the electrodes. Among the carbon supports, Carbon Black (Vulcan XC-72) has been commercially used as a carbon support for the Pt catalyst but this support material is easily affected from the operation conditions of PEMFCs originating from chemical contamination, operating temperature, voltage, etc. Graphene, with its superior properties such as high mechanical strength, high surface area, good conductivity and catalytic activity is one of the most important discoveries in the nanomaterial world and has been recently investigated as a support material for various applications. In this study, three different carbon supported Pt Nanoparticles (NPs), namely Pt/CB NPs (CB: Carbon Black), Pt/GNP NPs (GNP: Graphene Nanoplatelets), Pt/CB-GNP NPs (hybrid support material of Carbon Black and Graphene Nanoplatelets (50:50)), were synthesized by using the organometallic synthesis method. In this method, Ptx(dba)y complex has been decomposed on the chosen pure or hybrid carbon support material in the presence of H2 gas under mild reaction conditions. The resulting materials were fully characterized by using Raman Spectroscopy, X-Ray Diffraction Spectroscopy (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Brunauer-Emmett-Teller (BET). The Electrochemical characterization and the electrochemical surface area (ECSA) calculations were made by the Cyclic Voltammetry (CV) technique. Oxygen Reduction Reactions (ORR) were run using a Rotating Disc Electrode (RDE). Finally, the fuel cell performances of the chosen catalysts were tested using a Scribner 850e Fuel Cell Test Station. Among the three catalysts compared, the hybrid Pt/CB-GNP NPs were the most promising material as an electrocatalyst, in terms of both the structural properties and the electrochemical performance.
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