A water-resistant and stable Pd-Co3O4 catalytic interface for complete methane oxidation with insights on active structures and reaction pathway

Palladium-based catalysts have long been considered the benchmark for methane combustion; however, the authentic phase of catalytic active sites remains a subject of ongoing debate. Additionally, challenges like water-poisoning and long-term stability need to be addressed to advance catalyst performance. Herein, we investigate Pd on Co 3 O 4 nanorods as a highly effective catalyst for catalytic oxidation of methane, demonstrating long-term stability and water tolerance during a 100-h continuous operation at 350 °C. Comprehensive characterizations reveal the presence of an active Pd-oxygen vacancy (O v )-cobalt interface in Pd/Co 3 O 4 , which effectively adsorbs molecular O 2 . The absorbed oxygen species on this interface are activated and directly participate in methane combustion. Moreover, near-ambient pressure X-ray photoelectron spectroscopy demonstrates that Pd nanoparticles undergo a rapid phase transition and predominantly remain in the metallic state during the reaction. This behavior is attributed to the electronic metal-support interaction between Pd and Co 3 O 4 . Furthermore, in situ Fourier transformed infrared spectrum reveals that under reaction conditions, HCO 3 * species are formed initially and subsequently transformed into formate species, indicating that the formate pathway is the dominant mechanism for CH 4 oxidation.