Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Physical Chemistry

With an increasing energy demand and growing environmental concerns, the development of new energy sources becomes very urgent. Herein, a group of novel catalysts of manganese oxides (MnO{u0353} ), Nickel oxides (NiO{u0353} ), and their binary oxides MnO{u0353} & NiO{u0353} with different sequentially electrodeposition order which dispersed onto glassy carbon electrode (GCE) and graphene nanosheets (GNs) modified GCE were suggested as an efficient and durable way for enhancement of glucose oxidation reaction (GOR) and urea oxidation. The embedding of these nanostructured metal oxides in the GNs significantly enhanced their activity and stability for glucose and urea electrooxidation. Moreover, the amended GNs with a combination of those metal oxides (MnO{u0353} and NiO{u0353} , where NiO{u0353} is the top layer, (NiO{u0353} /MnO{u0353} ) showed the best electrocatalytic activity and stability for glucose and urea electrooxidation compared to in the unmodified or the modified GNs with their respective single oxides. {uF0B7} The oxidation peak current increases for glucose (more than 1.5 times) and (about 2 times) for urea oxidation at NiO{u0353} /MnO{u0353} /GNs/GC electrode compared with NiO{u0353} /MnO{u0353} /GC electrode. {uF0B7} NiO{u0353} /MnO{u0353} /GNs/GC electrode shows a higher stability for 7 hr. than that obtained at NiO{u0353} /MnO{u0353} /GC electrode. This proves a better mechanical stability and good adherence of the modified GNs. These outstanding enhancements are attributed to the synergistic effect between these two metal oxides (MO{u0353} ) and GNs matrix, where MnO{u0353} is believed to enhance the glucose and urea molecules adsorption and improve the NiO{u0353} NPs conductivity via increasing of the content of Ni3+ (NiOOH). Besides, GNs are believed to stabilize and increase of the nickel oxyhydroxide (NiOOH) surface concentration

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