Active sites and mechanisms for H2O2 decomposition over Pd catalysts

A combination of periodic, self-consistent density functional theory (DFT-GGA-PW91) calculations, reaction kinetics experiments on a SiO2-supported Pd catalyst, and mean-field microkinetic modeling are used to probe key aspects of H2O2 decomposition on Pd in the absence of cofeeding H-2. We conclude that both Pd(111) and OH-partially covered Pd(100) surfaces represent the nature of the active site for H2O2 decomposition on the supported Pd catalyst reasonably well. Furthermore, all reaction flux in the closed catalytic cycle is predicted to flow through an O-O bond scission step in either H2O2 or OOH, followed by rapid H-transfer steps to produce the H2O and O-2 products. The barrier for O-O bond scission is sensitive to Pd surface structure and is concluded to be the central parameter governing H2O2 decomposition activity.