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Heterolytic Hydrogen Activation: Understanding Support Effects in Water-Gas Shift, Hydrodeoxygenation, and CO Oxidation Catalysis

preprint
submitted on 23.10.2019 and posted on 25.10.2019 by Nicholas Nelson, János Szanyi
Identifying the role of oxide supports in transition metal catalysis is critical toward our understanding of heterogeneous catalysis. The water-gas shift (WGS) reaction is a prototypical example where oxide support dictates catalytic activity, yet the cause for this remains uncertain. Herein, we show that a single descriptor—the equilibrium constant for hydroxyl formation—relates the WGS turnover frequency across disparate oxide supports. The dissimilar equilibrium constant, or oxophilicity, between early and late transition metals exemplify the utility of metal-support interfacial sites to circumvent adsorption-energy scaling restrictions, thereby providing bifunctional gains for the WGS reaction class. In relation, the equilibrium constant for hydroxyl formation is equivalent to the equilibrium constant for the formal heterolytic dissociation of hydrogen, and therefore, reflects the ability of the metal-support interface to participate in hydrogen heterolysis. The ubiquitous coexistence, yet divergent chemical behavior of homo- and heterolytically activated hydrogen renders oxide support identity central toward our understanding of hydrogenation catalysis.

History

Email Address of Submitting Author

nelsonnicholasc@gmail.com

Institution

Pacific Northwest National Laboratory

Country

United States

ORCID For Submitting Author

0000-0002-5596-542X

Declaration of Conflict of Interest

no conflict of interest

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