Impact of oxidants O₂, H₂O, and CO₂ on graphene oxidation: A critical comparison of reaction kinetics and gasification behavior

Abstract

Fundamental understanding of the oxidation behavior of O
₂, H
₂O, and CO
₂ in the process of oxyfuel combustion is of great significance. Extensive MD simulations with reactive force-field (ReaxFF) were performed to compare the gasification behavior under the individual influence of three oxidant molecules on a pristine and a mono-vacant graphene sheet. Distinct differences were observed in almost every aspect including initial kinetics, rate changes, complete/incomplete combustion, gasified regions, and the role of vacancy defects. In the case of O
₂, the nucleation stage is harder while the later stages contained no limiting behavior; The gasification kinetics is highest for H
₂O during initial periods, but the oxidative behavior changes as higher gas consumption levels are reached; CO
₂ has the highest thermodynamic stability and the formation of stable intermediate structures troubles the gasification. Significant out-of-plane activity is observed in the case of H
₂O oxidant. Results suggest that there may be little overlap in the oxidation sites for CO
₂ and H
₂O. In-depth atomic level investigations consistent with the experimental phenomenon will have implications for future design, process optimization, and their commercial application.