Fig. 4: Mechanistic study.

a In situ DRIFT spectra of H2-activated Pd/C-O; b Pd and c O speciation of H2-activated Pd/C-O followed by NAP-XPS. d CHO acetal rate over Pd/C and Pd/C-O under different atmospheres. Reaction conditions: methanol (15 mL), reactant (0.09 mmol), temperature (110 °C), catalysts (20 mg), pressure (2.0 MPa), time (0.5 h). e Py-FTIR spectra and f NH3-TPD of Pd/C, Pd/C-O, H2-activated Pd/C and H2-activated Pd/C-O.