Investigating the stability of graphitic carbon materials in electrocatalysis using electronic structure methods

As carbon materials are cheap and versatile, they are widely used materials for heterogeneous catalysis in general and for electrocatalysis in particular. However, they are prone to degradation, particularly under oxidative conditions. While electronic structure theory has been applied to study structure and thermodynamics in materials science, in many cases kinetic stability is the key feature which is associated with mechanisms and barriers. To compute these in aqueous medium and under electrode potential, we devise a DFT + implicit solvation scheme using a constant potential approach. Considering both pH and potential on a polycyclic aromatic hydrocarbon (PAH) model, we find a low energy pathway for graphitic carbon degradation. Depending on the pH and the potential, barrierless hydroxylation followed by deprotonation is observed at the PAH's edges. At low pH and potential, the material is expected to remain pristine, at intermediate potential it exhibits few ketone and alcohol groups at its edges, and at high potential no barriers are found for hydroxylation processes, leading to CO2 formation and significant deformation of the material. We also observe smaller PAHs and nitrogen doped PAHs exhibit increased stability, which we attribute to their increased oxidation potentials. (C) 2020 Elsevier Ltd. All rights reserved.