Enhanced Electrochemical Oxygen Reduction By Modulating Electronic Structures of Platinum Nanoparticles By Nitrogen-Introduced Carbon Support

With universal attention to sustainable development, the eco-friendly generation of energy has been emerging as one of the most important projects. Fuel cells, electrochemical energy conversion devices using hydrogen as the energy source, are one of the key solutions to this urgent problem. To get an effective energy conversion efficiency, understanding the reaction of fuel cells that occurred in each part is essential. Oxygen reduction reaction (ORR), which occurred in the cathode, is the main reason for reducing the efficiency because of its sluggish reaction kinetics. Therefore, it is necessary to develop highly active ORR catalysts to get efficient fuel cells. Among the various elements, platinum (Pt) has been known as the best active metal for its optimized binding properties with oxygen so plenty of research related to Pt-based materials has been reported so far. Most of them focused on electrocatalytic active material such as Pt-alloy nanocrystals or facet-controlled nanostructures where the electrochemical reaction occurred, while the surface state of the support has been largely neglected. Generally, carbon support for nanocrystals has been regarded as inert for reaction pathways on metal nanocrystals. In this study, we demonstrate that surface N-functionalization of carbon support can modulate electronic structures of supported Pt nanocrystals. Electronic structure-modified Pt nanocrystals show less affinity toward oxygen adsorption species, which means attenuated surface coverage and thereby much higher availability of Pt active sites during electrocatalysis. Consequently, reaction kinetics and mass activity are remarkably improved as much as Pt-M (M=Transition metals) alloy nanocrystals. This study will suggest the importance of surface engineering in carbon support as a factor in enhancing the electrocatalytic performance of nano-particulate electrocatalysts.