单原子Cu催化剂还原燃煤烟气中NO的微观机理研究

Micro-mechanism of NO reduction in coal flue gas catalyzed by single atom Cu catalyst

单原子催化剂具有高原子利用率与高催化活性并已广泛应用于CO氧化、CO_(2)还原等领域,对单原子Cu催化剂在催化还原NO领域的微观机理研究有助于开发还原氮氧化物的新型单原子催化剂。阐述量子化学计算参数与模型构建,剖析基于Eley-Rideal(E-R)、Langmuir-Hinshelwood(L-H)吸附机理下的NO还原反应路径及N_(2)O还原反应路径,并对NO还原反应动力学进行分析,以密度泛函理论、经典过渡态理论为依据,探究石墨烯量子点担载单原子Cu催化剂(Cu/G)催化还原燃煤烟气中NO的微观反应机理。结果表明,Cu/G非均相还原NO包括N_(2)O的形成与N_(2)的形成2个阶段。由能垒角度分析,在E-R作用机制下,NO依次被还原生成N_(2)O和N_(2)的控速步骤能垒值为74.5 kJ/mol,小于L-H作用机制控诉步骤能垒值。由动力学角度分析,反应温度的升高提升了NO还原反应的速率。反应过程中活性氧的转移导致石墨烯量子点的消耗,随着活性氧转移速率的减弱,最终导致催化剂失活。单原子Cu催化剂催化还原NO的能垒值较金属Cu团簇能垒值有所降低,说明金属分散性对催化剂的活性产生直接影响,也证明单原子催化在还原NO领域具有潜在的前景。

Single-atom catalysts(SACs)exhibit high atomic utilization efficiency and superior catalytic activity,and have been widely applied in fields such as CO oxidation and CO_(2) reduction.The investigation of the micro-mechanisms of single-atom Cu catalysts in the catalytic NO reduction will contribute to the development of novel single-atom catalysts for the nitrogen oxides reduction.The parameters for quantum chemical calculations and model construction are described.The reaction pathways for NO reduction and N_(2)O reduction,based on the Eley-Rideal(E-R)and Langmuir-Hinshelwood(L-H)adsorption mechanisms,are analyzed.Additionally,the kinetics of the NO reduction reaction are studied.Based on density functional theory and classical transition state theory,the micro-mechanisms of heterogeneous NO reduction in coal flue gas catalyzed by single-atom copper catalysts supported on graphene quantum dots(Cu/G)were investigated.The results indicate that the reduction process on Cu/G involves two stages:the formation of N_(2)O and the formation of N_(2).Analysis of the energy barriers indicates that,within the Eley-Rideal(E-R)mechanism,the rate-determining steps for the sequential reduction of NO to N_(2)O and subsequently to N_(2)exhibit lower energy barriers,with a value of 74.5 kJ/mol,compared to those observed in the Langmuir-Hinshelwood(L-H)mechanism.Kinetic analysis demonstrates that an increase in reaction temperature enhances the rate of NO reduction.Throughout the reaction process,the transfer of active oxygen leads to the consumption of graphene quantum dots,and a subsequent decline in the active oxygen transfer rate ultimately results in catalyst deactivation.The energy barrier for the catalytic reduction of NO by single-atom Cu catalysts is lower than that of Cu metal clusters,indicating that the dispersion of metal atoms has a direct impact on catalytic activity.This also demonstrates the potential of single-atom catalysis in NO reduction.