Tandem Catalysis for Selective Oxidation of Methane to Oxygenates Using Oxygen over PdCu/Zeolite.

Selective oxidation of methane to oxygenates with O 2 under mild conditions remains a great challenge. Here we report a ZSM-5 (Z-5) supported PdCu bimetallic catalyst (PdCu/Z-5) for methane conversion to oxygenates by reacting with O 2 in the presence of H 2 at low temperature (120 °C). Benefiting from the co-existence of PdO nanoparticles and Cu single atoms via tandem catalysis, the PdCu/Z-5 catalyst exhibited a high oxygenates yield of 1178 mmol g -1 Pd  h -1 (mmol of oxygenates per gram Pd per hour) and at the same time high oxygenates selectivity of up to 95 %. Control experiments and mechanistic studies revealed that PdO nanoparticles promoted the in situ generation of H 2 O 2 from O 2 and H 2 , while Cu single atoms not only accelerated the activation of H 2 O 2 for the generation of abundant hydroxyl radicals (⋅OH) from H 2 O 2 decomposition, but also enabled the homolytic cleavage of CH 4 by ⋅OH to methyl radicals (⋅CH 3 ). Subsequently, the ⋅OH reacted quickly with the ⋅CH 3 to form CH 3 OH with high selectivity.