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THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Tuesday, September 4, 2018
2:00 PM
in MoSE 3201A
will be held the
DISSERTATION PROPOSAL DEFENSE
for
Ali Abdelhafiz Mahmoud
"Hybrid Catalyst for Low Temperature Oxygen Reduction Reaction: Investigating the Dual Role of Graphene as a Catalyst-support and Protective-cap for Atomic Scale Pt Catalyst"
Committee Members:
Prof. Meilin Liu, Advisor, MSE
Prof. Faisal Alamgir, Co-advisor, MSE
Prof. Preet Singh, MSE
Prof. Sundaresan Jayaraman, MSE
Prof. Mostafa El-Sayed, CHEM
Abstract:
Energy demand-supply relationship is a big concern with world’s consumption increased over 65% over the past 18 years. Moreover, carbon dioxide emissions increased with an associated serious weather changes, as known as “Global Warming”. Therefore, a dire need for a renewable and green energy source captured huge interest in the scientific community over the past two decades. Fuel cell technology arose as a prominent candidate where chemical energy is converted into electricity. Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a class of fuel cell powered by hydrogen gas as a fuel, which generates zero carbonaceous emissions (i.e. produce H2O). PEMFC operates at lower temperature (typically 80-200 °C) compared to other fuel cell categories, which enables them to be used for mobile applications (e.g. vehicles or electronic devices). One of the major challenges in PEMFC is the sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode side. State of the art catalyst for ORR in PEMFC is based on a precious metal (i.e. Pt). PEMFC commercialization is suppressed due to high cost and short lifetime of Pt catalyst component (i.e. 40% of PEMFC cost is due to Pt catalyst with operation limits well below 100 hours). Thus, producing a cost-effective, ORR catalytically active and highly durable catalyst is crucial for PEMFC technology spread.
Graphene captured great attention in catalysis due to its mechanical and chemical stability. In the proposed thesis, demonstrating the dual role for graphene, as both a platform for synthesis of single atoms to few atomic layer-thick Pt catalyst. In addition, serving as a ‘chemically transparent’ barrier to catalytic deactivation wherein graphene does not restrict the access of the reactants but does block Pt from dissolution or agglomeration. Several scientific ambiguities have to be clarified to enable a design of desirable ORR catalyst. Herein, effect of modifying graphene support, through heteroatom doping (chemistry and doping concentration), on catalyst atoms dispersion and stability have to be addressed. Moreover, the ligand effect (i.e. catalyst-underlayer) is thoughtful to influence Pt-adatoms catalytic activity. Unravelling the associated structural and chemical changes of atomic scale Pt/graphene architectures draws a roadmap to tailoring highly durable and cost-effective ORR catalysts. Preliminary results of the proposed architectures showed enhancement of ORR catalytic activity. in addition, graphene capping help retaining full activity of Pt-catalyst beyond 5000 testing cycles.
