期刊
ACS CATALYSIS
卷 12, 期 2, 页码 1024-1030出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.1c05947
关键词
active sites; NH3-SCR; selective passivation; reaction mechanism; metalfree carbon catalysis
资金
- National Natural Science Foundation of China [21876093, 52070114]
This study identifies the nucleophilic ketonic carbonyl groups as the intrinsic active sites for NO reduction on metal-free carbon catalysts through experimental and computational methods. The mechanism of the SCR reaction involving a redox cycle of ketonic carbonyl/phenol pairs is revealed, and it demonstrates analogous features with vanadyl catalysts, potentially parallel the SCR mechanisms on metal-free carbon catalysts to transition-metal catalysts.
Although carbon catalysts have been commercialized for the low-temperature selective catalytic reduction (SCR) of NO with NH3 for decades, the nature of the active sites remains unclear. Herein we design a proof-of-concept study to directly evidence that the nucleophilic ketonic carbonyl groups are the intrinsic SCR active sites on metal-free carbon catalysts through ex situ and in situ selective passivation strategies. The turnover frequency of the ketonic carbonyl group is provided, and the structure-reactivity relationship is established for the first time. Density functional theory calculations combined with in situ spectroscopy reveal that the standard carbon-catalyzed SCR reaction involves a redox cycle of ketonic carbonyl/phenol (C=O/C-OH) pairs, during which the activation of NH3 is the rate-limiting step. This work identifies the intrinsic SCR active sites and advances the metal-free carbon catalysis. As a further step, the carbon catalysts demonstrate analogous mechanistic features with vanadyl catalysts, opening up the possibility to parallel the SCR mechanisms on metal-free carbon catalysts to those on transition-metal catalysts on the atomic scale.
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