Operando TEM Study of Partial Oxidation of Methane Over Pd Nanoparticles

Methane (CH₄), which constitutes over 95% of low-cost and abundantly available natural gas reserves, represents a key feedstock for producing syngas and other value-added chemicals. Developing catalysts capable of efficiently converting CH₄ into these chemicals is, therefore, crucial for reducing the dependence on limited crude oil resources. Despite the importance of these conversion reactions, the underlying details of catalyst activity remain elusive. Here, using operando gas-cell transmission electron microscopy, the nanoscale mechanisms of the catalytic partial oxidation of CH₄ over Pd nanoparticles (NPs) are explored. The observations show that the onset of the catalytic reaction directly coincides with the transformation of these NPs into robust fragmented Pd-PdO NPs. Density functional theory calculations reveal that the Pd-PdO interface plays a pivotal role in optimizing the reaction pathway: metallic Pd facilitates CH₄ dehydrogenation, while PdO promotes C oxidation. These insights into the active structures of catalysts under working conditions provide a foundation for the rational design of high-performance catalysts.