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 O2, H2O, and CO2 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 O2, the nucleation stage is harder while the later stages contained no limiting behavior; The gasification kinetics is highest for H2O during initial periods, but the oxidative behavior changes as higher gas consumption levels are reached; CO2 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 H2O oxidant. Results suggest that there may be little overlap in the oxidation sites for CO2 and H2O. In-depth atomic level investigations consistent with the experimental phenomenon will have implications for future design, process optimization, and their commercial application.