Fig. 1: Stabilizing active palladium species on defective alumina sites.
From: Anchoring PdOx clusters on defective alumina for improved catalytic methane oxidation
a Schematic illustration of the synthesis of defective alumina (Al2O3-x) and Pd/Al2O3-x. 27Al solid state nuclear magnetic resonance (ssNMR) spectra and respective fitting for Al2O3-x (b bottom), Pd/Al2O3-x (b top), γ-Al2O3 (c bottom) and Pd/Al2O3 (c top) The deconvoluted peaks, denoted by blue, yellow, and red colors, respectively represent the tetrahedral, pentahedral, and octahedral coordination Al species. d Light-off curves for catalytic methane (CH4) oxidation over fresh and aged Pd/Al2O3 and Pd/Al2O3-x catalysts under reaction conditions (500 °C, 1.5 h). Reaction conditions: CH4:O2:He = 2:8:90, 50 mg catalyst, GHSV = 60,000 h−1. e Arrhenius plots of the fresh and aged Pd catalysts. The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of Pd/Al2O3-fresh (f, g); Pd/Al2O3-aged (h–j); Pd/Al2O3-x-fresh (k) and Pd/Al2O3-x-aged (l–n). The red and blue dashed boxes represent respectively the regions where PdOx clusters/nanoparticles (NPs) and single atoms are present on the catalysts. Pd clusters are marked with the red rings, while Pd single atoms are marked with blue rings.
