Fabrication and Characterization of Efficient Nanostructured Modified Electrodes for Fuel Cell Applications

Abstract

The global demands for renewable energy resources replacing the traditional fossil fuels and the urgency to sustain green societies have motivated intensively research on the development of fuel cells (FCs). For long time, the typically manufactured and investigated FC has utilized hydrogen (H2) gas as the fuel and oxygen (from air) as the oxidant. But the replacement of H2 with safer liquid fuels which can easily be stored and transported has been taken place to reduce the hazardous of H2 gas. In this regard, the direct methanol fuel cell (DMFC), which depends on the methanol electro-oxidation reaction (MOR) was designed, proved efficient and produced large energy density. The aim of this thesis contains several tasks targeting the development of efficient Pt-based nano-catalysts for MOR. These catalysts are classified generally into two categories; the first used a poly crystalline Pt substrate and the other used nano-Pt, which was deposited on a GC substrate, as bases for further modifications. Several transition metal oxide nanostructures as nano-NiOx, nano-MnOx and nano-CoOx have been deposited with various loadings and/or combinations on the Pt based substrates to improve the catalytic activity and stability of these catalysts towards MOR. FE-SEM and EDS have been employed Summary of the Thesis 228 to reveal, respectively, the substrate morphology and the bulk composition of the modified electrodes. As well, linear sweep voltammetry (LSV) was used to measure the electrocatalytic activity of the modified electrodes towards MOR. Interestingly, the highest catalytic enhancement for MOR was achieved at the ternary modified GC electrodes, namely, MnOx/NiOx/Pt/GC and CoOx/MnOx/Pt/GC electrodes. However, CoOx/MnOx/Pt/GC electrode provided higher stability towards MOR with prolonged time of continuous electrolysis. This was attributed to the incorporation of nano-CoOx in the catayst’s composition; nano-CoOx has played an essential role in increasing the mechanical stability of the NPs at the electrode surface and its tolerance against CO poisoning as well. In addition, tests for the influence of operating pH at these two electrodes (MnOx/NiOx/Pt/GC and CoOx/MnOx/Pt/GC) towards MOR were employed. MOR was found to be pH dependent; as pH was increased, MOR was consequently increased.