Atomic-scale insights into zeolite-based catalysis in N2O decomposition
Atomic-scale insights into zeolite-based catalysis in N2O decomposition
复制标题
N2O 分解中沸石催化的原子尺度见解
DOI：
10.1016/j.scitotenv.2019.03.481
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发表时间：
2019
影响因子：
9.8
通讯作者：
Yulong Shan
中科院分区：
文献类型：
--
作者：
Guangzhi He;Bo Zhang;Hong He;Xueyan Chen;Yulong Shan
一氧化二氮（N2 O）是21世纪最严重的臭氧消耗物质。沸石基催化剂是一种非常有前途的大规模工业应用的N2 O去除方法。然而，沸石分子筛中的过渡金属交换物种对催化剂的性能有很大影响。控制催化活性的主要因素是一个激烈争论的话题，仍然高度不确定。本文合成了一系列过渡金属离子（Fe，Co，Ni，Cu）交换的ZSM-5分子筛催化剂。实验和密度泛函理论（DFT）计算均表明，催化剂对N2 O的分解活性顺序为Fe> Co > Ni > Cu。电子结构性质分析表明，过渡金属离子交换ZSM-5分子筛的催化活性受活性位的局部软度和HOMO组成的影响。局部柔软度和HOMO中4s轨道的比例越高，催化活性就越高，这有利于氧化还原过程中的电子转移，从而降低N2 O分解为N2和O2的反应垒。阐明催化活性的本质有助于加深对分子筛催化原理的理解，有助于设计高效的分子筛催化剂。
Nitrous oxide (N2O) has been the most serious ozone-depleting species throughout the 21st century. Zeolite-based catalysis is a highly promising method for N2O removal in large-scale industrial applications. However, the exchanged transition metal species in zeolites greatly influence the performance of catalysts. The primary factor governing the catalytic activity is a fiercely debated topic and remains highly uncertain. Here we synthesize a series of transition-metal ion (Fe, Co, Ni, Cu)-exchanged ZSM-5 zeolite catalysts. Both experiments and density functional theory (DFT) calculations demonstrate that the activity for N2O decomposition follows the order Fe ≈ Co > Ni > Cu. Analysis of the electronic structure properties reveals that the catalytic activity of the transition-metal ion-exchanged ZSM-5 zeolites is governed by the local softness of active sites and the composition of their HOMOs. The higher the local softness and the proportion of 4s orbitals in the HOMO, the higher the catalytic activity, which facilitates electron transfer in the redox process and thereby reduces the reaction barriers for N2O decomposition into N2and O2. Clarification of the nature of catalytic activity advances the understanding of the principles of zeolite-based catalysis, and is helpful for the design of highly efficient zeolite catalysts for pollutant removals.