A DFT study of the mechanism of H transfer during steam gasification

The chemical reaction between a graphite model edge and H₂O is crucial in steam gasification. This study used density functional theory (DFT) calculations to systematically evaluate the reaction path of steam gasification. The research results indicate that a graphite model edge without active cites is more suitable for use as an initial model for steam gasification. The aromaticity of the graphite model edge and the desorption of CO are linearly related. H atoms from H₂O are transferred to the graphite model edge, destroying the aromaticity of the edge carbon structure and facilitating the subsequent desorption process, which may be the cause of the higher reactivity of steam compared to CO₂ gasification. From a thermodynamic perspective, hydrogen transfer may be the rate-determining step of the overall reaction. The results of this paper can explain the kinetic differences in previous experiments that used water with varying isotopes of H (H₂O vs D₂O) and graphite in the gasification reaction (Yates and McKee, 1981; Mims and Pabst, 1987; Fletcher and Thomas, 2007). Our results provide new insights into the H transfer mechanism in steam gasification.