Regulating oxygen activity of perovskites to promote NOx oxidation and 
reduction kinetics

Hwang, Jonathan; Rao, Reshma R.; Giordana, Livia; Akkiraju, Karthik; Wang, Xiao Renshaw; Crumlin, Ethan J.; Bluhm, Hendrik; Shao-Horn, Yang

doi:10.1038/s41929-021-00656-4

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Regulating oxygen activity of perovskites to promote NO_x oxidation and reduction kinetics

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Bluhm, Hendrik
Advanced Light Source, Lawrence Berkeley National Laboratory;
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;
Chemical Sciences Division, Lawrence Berkeley National Laboratory;

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Citation

Hwang, J., Rao, R. R., Giordana, L., Akkiraju, K., Wang, X. R., Crumlin, E. J., et al. (2021). Regulating oxygen activity of perovskites to promote NO_x oxidation and reduction kinetics. Nature Catalysis, 4. doi:10.1038/s41929-021-00656-4.

Cite as: https://hdl.handle.net/21.11116/0000-0008-F055-9

Abstract

Understanding the adsorption and oxidation of NO on metal oxides is of immense interest to environmental and atmospheric (bio)chemistry. Here, we show that the surface oxygen activity, defined as the oxygen 2p-band centre relative to the Fermi level, dictates the adsorption and surface coverage of NO_x and the kinetics of NO oxidation for La_1−xSr_xCoO₃ perovskites. Density functional theory and ambient-pressure X-ray photoelectron spectroscopy revealed favourable NO adsorption on surface oxygen sites. Increasing the surface oxygen activity by increasing the strontium substitution led to stronger adsorption and greater storage of NO₂, which resulted in more adsorbed nitrogen-like species and molecular nitrogen formed upon exposure to CO. The NO oxidation kinetics exhibited a volcano trend with surface oxygen activity, centred at La_0.8Sr_0.2CoO₃ and with an intrinsic activity comparable to state-of-the-art catalysts. We rationalize the volcano trend by showing that increasing the NO adsorption enhances the oxidation kinetics, although NO adsorption that is too strong poisons the surface oxygen sites with adsorbed NO₂ to impede the kinetics.