Mechanistic Insights on the Low-Temperature Oxidation of CO Catalyzed by Isolated Co Ions in N-Doped Carbon
Mechanistic Insights on the Low-Temperature Oxidation of CO Catalyzed by Isolated Co Ions in N-Doped Carbon
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DOI：
10.1021/acscatal.2c04380
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发表时间：
2022-12
期刊：
影响因子：
12.9
通讯作者：
Colby A. Whitcomb;Anna Sviripa;Michael I. Schapowal;K. Mamedov;R. Unocic;Christopher Paolucci;R. Davis
中科院分区：
文献类型：
--
作者：
Colby A. Whitcomb;Anna Sviripa;Michael I. Schapowal;K. Mamedov;R. Unocic;Christopher Paolucci;R. Davis
掺氮碳(Co-N-C)上的孤立钴离子可在低至196K的温度下催化CO氧化，但该反应的活性中心和反应机理尚不清楚。在本工作中，在Co-N-C催化剂上273K附近的稳态CO氧化显示出CO和O2的近乎一级行为以及负的表观活化能。反应的同位素瞬变分析证实，快速的周转频率和低表面覆盖率的吸附中间产物导致二氧化碳(<；10%的钴)。动力学实验结合量子化学计算和分子动力学模拟的结果与CO在Co离子上的弱吸附和CO辅助活化弱吸附O2的低势垒的反应路径一致。提出的氧气活化机理不涉及与过渡金属离子的氧化还原循环，在其他涉及氧气的低温催化反应中可能是重要的。
Isolated cobalt ions on nitrogen-doped carbon (Co–N–C) catalyze CO oxidation at temperatures as low as 196 K, but the active site and mechanism for this reaction remain elusive. In this work, steady-state CO oxidation around 273 K over Co–N–C revealed nearly first-order behavior in both CO and O2as well as a negative apparent activation energy. Isotopic transient analysis of the reaction confirmed a rapid turnover frequency and low surface coverage of adsorbed intermediates leading to CO2(<10% of the Co). Results from kinetics experiments combined with quantum chemical calculations and molecular dynamics simulations are consistent with a reaction path involving weak adsorption of CO onto Co ions followed by a low barrier for the CO-assisted activation of weakly adsorbed O2. This proposed mechanism for dioxygen activation does not involve a redox cycle with the transition-metal ion and may be important in other low-temperature catalytic reactions involving O2.