Metal-Organic framework/graphene oxide derived porous carbons for platinum based electrocatalysts for oxygen reduction reaction

Official URL: http://risc01.sabanciuniv.edu/record=b2066329 (Table of Contents)

Fossil fuel-based energy economy is bound to change at some point within the 21st century as fossil fuels are inherently limited sources. Energy conversion and storage devices such as batteries, fuel cells, solar cells and supercapacitors need to advance in terms of efficiency for the fruition of a renewable energy ecosystem. Hierarchically porous materials are utilized as catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs) and batteries to increase mass transfer and active site density in the catalyst. Metal-organic frameworks (MOFs) are tailorable crystalline solids where organic linker units are connected to metal centers. They may form molecular gates, channels and pores within the framework in angstrom to nanometer scale. Porous carbons derived from metal-organic frameworks are promising catalyst supports owing to their high surface area and 3-D network structure. In this thesis, a porous carbon has been produced from pyrolysis of a hybrid material based on Zn based MOF called zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO). As observed by physical and chemical characterization, ZIF-8 were coordinated to GO during the synthesis conditions of ZIF-8 and formed a hybrid structure in contrast with simple mixing. Evolution of macro/mesoporosity have been observed when the hybrid was exposed to pyrolyzing temperatures owing to the exfoliating effect of GO on ZIF-8. Pt nanoparticle (Pt NP) deposition on this porous carbon has resulted in catalyst Cat-1, which has been tested via voltammetric experiments against two reference materials; Pt decorated on pyrolyzed ZIF-8 (Cat-0) and Pt decorated on reduced GO (Pt/rGO). Cat-1 exhibits increased mass and specific activity against Pt/rGO at 0.8 V for oxygen reduction reaction (ORR). The nature of increased activity is proposed to be increased mass transport properties of Cat1 sample that originates from its hierarchical porosity.