Adsorption of NOx Molecules on the Hematite Surface: Isolated Versus Paired
Adsorption of NOx Molecules on the Hematite Surface: Isolated Versus Paired
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DOI：
10.1021/acs.jpcc.3c06774
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发表时间：
2024-02
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影响因子：
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通讯作者：
Yi-Bo Liang;Cui-Xia Wu;Tao Sun;Stefano Fabris;Lin Du
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作者：
Yi-Bo Liang;Cui-Xia Wu;Tao Sun;Stefano Fabris;Lin Du
赤铁矿是一种很有前途的催化剂，用于去除大气中的氮氧化物（NOx，x= 1和2）污染物。提高其催化性能需要清楚地了解相关的表面过程，包括NOx吸附。之前的理论模拟仅限于静态条件下的孤立吸附物，结果与实验不完全一致。本文采用带有货车der Waals修正的密度泛函理论+U方法研究了NOx分子在赤铁矿（0001）表面的吸附.我们发现，在静态条件下，由于两个开壳层NOx分子之间的协同效应，NOx倾向于同时占据两个相邻的表面Fe和O位置[J. Phys. Chem. B2002，106，7405-7413]。相比之下，孤立的吸附物在高温（T）或低NOx分压（PNOx），由于其较高的构型熵的青睐。一个表面相图构建的NOx吸附，描绘他们的稳定领域和平衡覆盖。由于NOx吸附物的结构和丰度强烈地依赖于T-PNOx，因此在不同T-PNOx条件下的表面反应可能遵循完全不同的途径。
Hematite is a promising catalyst to remove nitrogen oxide (NOx,x= 1 and 2) pollutants from the atmosphere. Improving its catalytic performance requires a clear understanding of the relevant surface processes, including NOxadsorption. Prior theoretical simulations were limited to isolated adsorbates at static conditions, with results not fully consistent with experiments. Here, we investigate the adsorption of NOxmolecules on the hematite (0001) surface by using the density functional theory +Umethod with van der Waals corrections. We find that, at static conditions, NOxprefer to occupy two neighboring surface Fe and O sites simultaneously, due to a cooperative effect between two open-shell NOxmolecules [J. Phys. Chem. B2002,106,7405–7413]. In contrast, isolated adsorbates are favored at high temperatures (T) or low NOxpartial pressures (PNOx) due to their higher configurational entropy. A surface phase diagram is constructed for the NOxadsorbates, delineating both their stability fields and equilibrium coverages. As the structure and abundance of NOxadsorbates depend strongly onTandPNOx, surface reactions at differentT-PNOxconditions may follow quite different pathways.