Rationalized Onion-like Non-PGM Catalyst Development for Oxygen Reduction Reaction

Abstract

Fuel cell technology is a green alternative to conventional combustion engine technology. At the cathode of the fuel cell, the oxygen reduction reaction (ORR) takes place. The state-of-the-art catalysts for this reaction are platinum (Pt)-based materials. At the fuel cell’s anode, Pt-based catalyst is also needed. The limited activation and reduction of oxygen on the cathode force to increase the loading of Pt-catalysts when compared to the anode. As a result, the practical fuel cell application is constrained by the expensive and volatile price of the Pt-market; the Pt-catalysts represent the 40% of the cost of the fuel cell. The development of inexpensive non-Pt catalysts are the center of investigation in the last decades and the development of non-Pt group metal (Non-PGM) catalysts, nitrogen-doped carbon materials, are promising alternatives. These are, typically, synthesized from metal salts and organic nitrogen and carbon precursors. The precursors are pyrolyzed at elevated temperatures, in an inert environment, to form the active structures for oxygen reuction catalysis. N-doped onion-like carbon nanostructures have being developed to achieve ORR catalysis. However, the mechanism of formation of these structures is not very well understood nor controlled. In this research, we aimed to rationally control the active site nanoarchitectures for ORR in acid media. Onion-like nanoarchitectures are developed as catalytic structures by handling the chemistry of the carbon and nitrogen precursors and the reaction leading to the formation of the onion-like nanostructures. These structures are inserted in a carbon-based conductive matrix that serves as electron collector. Results show these controlled nanoarchitectures are promising Non-PGM materials for ORR catalysis. Steele, B. C. H.; Heinzel, A. Materials for Fuel-Cell Technologies. Nature 2001, 414, 345–352. Shao, Y. Y.; Liu, J.; Wang, Y.; Lin, Y. H. Novel Catalyst Support Materials for PEM Fuel Cells: Current Status and Future Prospects. J. Mater. Chem. 2009, 19, 46–59. Wu, G.; Nelson, M.; Ma, S.; Meng, H.; Cui, G.; Shen, P. K. Carbon. 2011, 49, 3972-3982.