Structural insight into palladium-nickel clusters over mordenite zeolite for carbene-insertion reaction

The advancement of heterogeneous catalysts incorporating metal clusters in the nanometric size range has garnered significant attention due to their extraordinary catalytic activity and selectivity.The detailed characterization and understanding of the atomic structure of these metal clusters within catalysts is crucial for elucidating the underlying reaction mechanisms.In the present study,a distinctive three-atom PdNi cluster,characterized by two Pd atoms at terminal positions and a central Ni atom,was synthesized over mordenite zeolite.The presence of atomic PdNi clusters within the eight-membered ring side pocket area was confirmed by multiple advanced analytical techniques,including magic-angle spinning nuclear magnetic resonance spectroscopy,synchrotron X-ray powder diffraction,extended X-ray absorption fine structure spectroscopy,and high-angle annular dark-field scanning transmission electron microscopy.The catalytic activity of the confined active species was examined by the carbene-mediated reactions of ethyl-2-diazoacetate to ethyl-2-methoxyacetate as a model reaction.Compared to the Pd-mordenite and Ni-mordenite,the PdNi-mordenite catalyst incorporates a PdNi cluster,which demonstrates a superior performance,achieving 100%conversion and high selectivity under the same reaction conditions.Our study elucidates the potential of constructing bimetallic clusters in zeolites,providing valuable insights for developing new heterogeneous catalysts applicable to a wide range of catalytic processes.

Tunable catalytic activity of gadolinium-doped ceria nanoparticles for pro-oxidation of hydrogen peroxide

We report a study of the roles of gadolinium(lll)(Gd3+)dopants in influencing the catalytic activity of gadolinium-doped ceria nanoparticles towards the pro-oxidation of hydrogen peroxide to hydroxyl radicals.These doped ceria nanoparticles with dopant concentrations of 0.6 wt.%,3 wt.%,and 6 wt.%Gd^3+were synthesized using an ozone-mediated method for tuning their catalytic activities.The Gd dopants were found to foster an increase in the percentage of Ce^3+ions in the doped ceria nanoparticles.Our reaction kinetic study revealed that the relationship between the overall reaction rates and the Gd dopant concentrations in our doped materials followed a volcano-like trend.In contrast,the apparent activation energy values of these Gd-doped ceria nanoparticles were found to be positively associated with the concentrations of Gd dopants.The overall catalytic activity trend was attributed to the interplay between the promotion and degradation effects of the Gd dopants on the properties of doped ceria nanoparticles.