摘要: As a highly reactive reaction intermediate, surface gallium hydride (Ga-H) has garnered significant attention due to its critical role in various catalytic reactions. However, the detailed experimental characterization of this unique species remains challenging. Recently, we demonstrated that solid-state NMR can be an effective tool for studying surface Ga-H. In this work, we report a comparative solid-state NMR study on H2 activation over different Ga2O3 polymorphs, specifically α-, β- and γ-Ga2O3. 1H solid-state NMR enabled the identification of Ga-H species formed on all the three samples following high-temperature H2 treatment. The characteristic 1H NMR signals of the Ga-H species were resolved using J-coupling-based double-resonance NMR methods, revealing highly similar lineshapes of Ga-H for all the Ga2O3 samples. This suggests potentially similar surface Ga-H configurations among the different Ga2O3 polymorphs. In addition, the local hydrogen environments on the oxide surfaces were further explored using two-dimensional (2D) 1H-1H homonuclear correlation spectra, revealing multiple spatially proximate Ga-H pairs and Ga-H/-OH pairs on different Ga2O3 polymorphs. These findings provide insights into the potential mechanism of H2 dissociation. Overall, this work offers new perspectives on the local structure of surface Ga-H on Ga2O3, and the analytical approach presented here can be further extended to the study of other Ga-based catalysts and other metal hydride species.