A proposal based on quantum phenomena for the ORR mechanism on nitrogen-doped carbon-based electrocatalysts

Several theories have tried to explain the role of nitrogen-doped carbon-based electrocatalysts during the oxygen reduction reaction (ORR). However, there is no consensus about which of the existing theories is most accurate. In this work, we propose a hypothesis presented for the first time, which consists on the hybridization change of carbon atoms in the graphene lattice, from sp(2) to sp(3). As shown in several studies, carbons with sp(3) hybridization can store electrons (i.e. work as capacitors), this phenomenon, along with nitrogen inversion, due to lattice defects, would allow the nitrogen atom to works as a switch, enabling or stopping the flow of electrons, generating active sites that enhance the ORR. Computational chemistry was used to prove this hypothesis. A graphene of 92 atoms doped and undoped has been constructed using the Gauss View 5.0 (R) program, the geometries were optimized by DFT in Gaussian 0.9 (R) software, in order to compare changes in bond angles and lengths of the lattices, and map the electrostatic potential distribution (ESP). The results obtained in the measurement of the angles and charges around the doping nitrogen presented interesting results that can help to demonstrate part of the established hypothesis about nitrogen inversion. The study shows that it is possible that this phenomenon increases when there are a greater number of defects in the lattice. Understanding this phenomenon will help to develop and know the best synthesis conditions for doped carbon electrocatalysts. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.