Theoretical Investigation of H2 Combustion on alpha-Al2O3 Support

摘要

Based on Density Functional Theory - Generalized Gradient Approximation calculations (DFT-GGA), we provide a theoretical model for the effect of the catalytic support (alpha-Al2O3, aluminum oxide) on the dissociation of H2, O2, OH, H2O, and the surface diffusion of oxygen and hydrogen species along the alpha-Al2O3 (0001) surface. These processes are key to understanding the 'inverse spillover effect' that occurs during hydrogen combustion on alumina surfaces. Our results indicate the dissociation of O2 is not thermodynamically favored on the alpha-Al2O3 surface. However, both H2 and H2O can dissociate, forming hydroxyls with oxygen atoms in the second atomic layer. Once dissociated, oxygen species can diffuse locally but encounter a large barrier to long-range surface diffusion in the absence of defects or other species. In contrast, the barrier to the long-range surface diffusion of hydrogen is modest under ideal conditions.