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

• Published in: Chinese journal of catalysis Vol. 74; pp. 191 - 201
• Main Authors: Xu, Yuanjie, Hou, Run, Chi, Kunxiang, Liu, Bo, An, Zemin, Wu, Lizhi, Tan, Li, Zong, Xupeng, Dai, Yihu, Xie, Zailai, Tang, Yu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2025
• Subjects: Co3O4; Complete oxidation; Methane combustion; Near-ambient pressure X-ray photoelectron spectroscopy; Oxygen activation; Palladium catalyst; Water tolerance; Oxygen activation; Palladium catalyst; Near-ambient pressure X-ray photoelectron spectroscopy; Complete oxidation; Methane combustion; Water tolerance; Co3O4
• ISSN: 1872-2067
• DOI: 10.1016/S1872-2067(25)64728-0

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 Co3O4 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 (Ov)-cobalt interface in Pd/Co3O4, which effectively adsorbs molecular O2. 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 Co3O4. Furthermore, in situ Fourier transformed infrared spectrum reveals that under reaction conditions, HCO3* species are formed initially and subsequently transformed into formate species, indicating that the formate pathway is the dominant mechanism for CH4 oxidation. The Pd/Co3O4 catalyst exhibit high stability and water tolerance for methane oxidation. In situ characterizations reveal that the presence of an active Pd-oxygen vacancy (Ov)-cobalt interface in Pd/Co3O4 plays a crucial role for water resistance.