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Exploring Metal–Support Interactions To Immobilize Subnanometer Co Clusters on γ–Mo2N: A Highly Selective and Stable Catalyst for CO2 Activation

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journal contribution
posted on 06.09.2019, 13:03 by Siyu Yao, Lili Lin, Wenjie Liao, Ning Rui, Na Li, Zongyuan Liu, Jiajie Cen, Feng Zhang, Xing Li, Liang Song, Luis Betancourt De Leon, Dong Su, Sanjaya D. Senanayake, Ping Liu, Ding Ma, Jingguang G. Chen, José A. Rodriguez
Strong bonding interactions between a transition metal and a substrate or support is one of the most effective strategies to immobilize subnanometer scale clusters or atoms in heterogeneous catalysis. We show that such a type of phenomenon can take place on a Mo2N surface. Combined experimental and theoretical studies show that strong metal–support interactions between face-centered cubic-structured γ-Mo2N and cobalt have been confirmed to effectively anchor subnanometer Co clusters and prevent their aggregation. The results of X-ray absorption near edge structure, ambient pressure X-ray photoelectron spectroscopy, and density functional theory revealed electronic perturbations in the nitride-bonded cobalt not seen on a strongly active oxide such as CeO2. A charge transfer from Co to Mo2N was observed with a significant stabilization of the Co 3d levels, which prevents the full decomposition of CO2. The subnanometer Co loaded on γ-Mo2N catalysts exhibited very high selectivity to the product CO, whereas the undesirable methanation activity, typically inevitable on traditional Co/oxide catalysts, was successfully suppressed. As a consequence of the electronic perturbations induced by the nitride, the cobalt was not able to fully dissociate the CO2 molecule to generate C or CHx fragments necessary for methane production. Under reaction conditions, the strong bonding between Co and γ-Mo2N maintained the subnanometer geometry of Co, leading to a remarkable selectivity and stability.