Dual nanoparticle/substrate control of catalytic dehydrogenation

Several experimental techniques and first-principles quantum-mechanical calculations were combined to provide atomic-scale understanding of alumina/chromia systems, the oxidative dehydrogenation of alkanes, and the nanoparticle-substrate interactions that control catalytic activity. Direct imaging was used by Z-contrast aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) coupled with extended X-ray absorption fine structure (EXAFS) measurements. The EELS spectra clearly showed the presence of Cr and no discernible difference in Cr concentrations between different areas of the sample. Density functional calculations were used to explore the catalytic dehydrogenation of alkanes at the atomic level. Z-contrast STEM and EELS studies have demonstrated that while Cr is segregated into patches on γ-Al₂O₃ surface, it is distributed uniformly on η-Al₂0₃.