Alkaline Ammonia Fuel Cells Optimization, Performance on Microgravity and Synthesis of Pt Boron Doped Diamond Catalysts
Acevedo Esteves, Raúl
Cabrera, Carlos R. (Consejero)
This thesis comprises the study of different aspects of the electrochemical oxidation of Ammonia including its study in microgravity. Platinum on Ketjeblack and Platinum on Vulcan catalysts were synthesized, characterized and tested electrochemically in half cells in microgravity and compared with results on the ground. Electrodes made of Platinum micropillars with different geometries were tested in microgravity to study the effect of capillarity induced by the micropillars to counter the effect of lack of buoyancy on the oxidation of Ammonia. A study of the chronoamperometric performance of the electrochemical oxidation of Ammonia in an alkaline fuel cell was done. Under microgravity the performance of a fuel cell is diminished by the absence of buoyancy since nitrogen gas is produced. The following catalysts were studied: Platinum nanocubes, Platinum nanocubes on a Vulcan carbon support and Platinum on carbon nano-onion support. These nanomaterials were studied in order to search for catalysts conformations that may reduce or counter the loss of Ammonia oxidation performance under microgravity conditions and for space applications. Fuel Cell Membrane Electrode Assemblies (MEA) were made for use with Direct Ammonia Alkaline Fuel Cells. Platinum Black and Platinum on carbon nano-onion were used as catalysts and tested with hydrogen and Ammonia fuels. Two different gas diffusion layers were used in MEA one is carbon cloth with Teflon and the other in carbon paper without Teflon. Open circuit voltages and linear polarization curves were obtained to compare their performances. Finally a Platinum on Boron doped diamond catalyst was synthesized using the Rotating Disk Slurry Electrode method and tested electrochemically to observe its capacity to oxidize Ammonia.