Ab Initio Insights into the Early Stages of Methane Dehydroaromatization on Gallium Nitride

Methane dehydroaromatization (MDA) offers a promising non-oxidative route for converting methane into value-added aromatic hydrocarbons. Wurtzite gallium nitride (GaN) has demonstrated catalytic activity for this transformation at temperatures as low as 450°C, although the underlying mechanism remains incompletely understood. In this study, the initial steps of MDA on the GaN m-plane surface were investigated using density functional theory. A low-barrier pathway for methylene (CH₂) formation was identified, enabled by the migration of surface methyl and hydrogen species with similarly low barriers. This mechanism significantly lowers the activation barrier relative to previous estimates. Beyond dehydrogenation and migration, we examined the coupling of C₁ intermediates to form C₂ species, including ethyl, ethane, and ethylene. C-C bond-formation steps leading to ethane and ethylene were found to proceed with barriers comparable to that of CH₂ formation. These results indicate that methane activation on GaN is not governed by a single high-barrier step; instead, dehydrogenation, migration, and coupling each contribute comparable kinetic bottlenecks. Overall, the findings revise the mechanistic understanding of methane activation on GaN and underscore the importance of site availability and adsorbate mobility in enabling selective low-temperature reactivity.