Assessing the Effect of Dopants on the C-H Activation Activity of γ-Al2O3 using First-Principles Calculations

In recent years, the high availability of methane in the shale gas reserves has raised significant interest in its conversion to high-valuable chemicals but this process is still not commercially viable. Metal oxides, due to their surface heterogeneity and the presence of Lewis acidic and basic site pairs are known to facilitate the activation of C-H bonds of methane. In this work, we investigate the C-H bond activation of methane on pristine and doped gamma-Al2O3 clusters using density functional theory (DFT) calculations. Our results demonstrate that the polar pathway is energetically preferred over the radical pathway on these systems. We found that the metal dopants (boron and gallium) not only alter the catalytic activity of dopant sites but this effect is more pronounced on some of the adjacent sites (non-local). Among the selected dopants, gallium greatly improves the catalytic activity on most of the site pairs (including most active and least active) of pristine gamma-Al2O3. Additionally, we identified a correlation between H-2 binding energies and the C-H activation free energies on Ga-doped gamma-Al2O3.