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

[Display omitted] • In-depth atomic scale investigations of graphene gasification with O 2 , H 2 O and CO 2. • Differences in kinetics and atomic behavior of the three oxidants were observed. • Significant out-of-plane activity was noted in the case of H 2 O oxidant. • The oxidation with CO 2 and H 2 O may not be occurring on the same active sites. Fundamental understanding of the oxidation behavior of O 2 , H 2 O, 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 2 O 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 2 O oxidant. Results suggest that there may be little overlap in the oxidation sites for CO 2 and H 2 O. In-depth atomic level investigations consistent with the experimental phenomenon will have implications for future design, process optimization, and their commercial application. [ABSTRACT FROM AUTHOR]