Nature Catalysis ( IF 37.8 ) Pub Date : 2021-07-22 , DOI: 10.1038/s41929-021-00656-4 Jonathan Hwang 1 , Karthik Akkiraju 1 , Yang Shao-Horn 1, 2, 3 , Reshma R. Rao 2 , Livia Giordano 3 , Xiao Renshaw Wang 4 , Ethan J. Crumlin 5 , Hendrik Bluhm 5, 6, 7
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 NOx and the kinetics of NO oxidation for La1−xSrxCoO3 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 La0.8Sr0.2CoO3 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.
中文翻译:
调节钙钛矿的氧活性以促进 NOx 氧化和还原动力学
了解 NO 在金属氧化物上的吸附和氧化对环境和大气(生物)化学具有重大意义。在这里,我们表明,定义为相对于费米能级的氧 2 p带中心的表面氧活性决定了 NO x的吸附和表面覆盖以及 La 1- x Sr x CoO 3钙钛矿的 NO 氧化动力学. 密度泛函理论和环境压力 X 射线光电子能谱揭示了表面氧位点上有利的 NO 吸附。通过增加锶取代来增加表面氧活性导致更强的吸附和更大的 NO 2储存, 这导致更多吸附的类氮物质和暴露于 CO 时形成分子氮。NO 氧化动力学表现出具有表面氧活性的火山趋势,以 La 0.8 Sr 0.2 CoO 3为中心,具有与-最先进的催化剂。我们通过表明增加 NO 吸附会增强氧化动力学来合理化火山趋势,尽管过强的 NO 吸附会使吸附的 NO 2使表面氧位点中毒以阻碍动力学。