Modeling the Oxygen Reduction Reaction on

Atmospheric carbon dioxide levels are higher than they have been in the last million years. The environmental concerns associated with anthropogenic carbon pollution have motivated investment in alternative energy sources. Polymer electrolyte membrane fuel cells (PEMFCs) are one such candidate, utilizing hydrogen as the energy carrier. However, the sluggish kinetics of the oxygen reduction reaction (ORR) at the cell cathode and the high cost of the platinum catalyst are the main barriers to commercialization. As a result, much effort has gone into investigating non-precious metal catalytic materials to reduce platinum loading. Experimentally, nitrogen-doped graphene materials (CNx) have shown promise for their ORR activity. However, the chemical nature of the active site is subject to much debate. This study utilizes density functional theory (DFT) to model the elementary steps of the ORR on CNx. The free energies of each reaction intermediate are used to derive the onset potential, where current is experimentally observable. Water molecules are explicitly included in the model to simulate solvation at the cathode. These results are used to evaluate the application of solvation corrections developed for Pt(111). Following the introduction of a water bilayer into the system, the results exhibit relative agreement to the proposed constant solvation corrections, but are quantitatively variant. These findings suggest that the Pt(111) solvent corrections do not entirely translate to these materials, and the explicit inclusion of water may be necessary to properly evaluate solvent effects on the ORR activity of CNx. The extension of these methods to modeling on nitrogen defects on graphene edge sites and TM-CNx surfaces is discussed. i