Adsorption of NO2 and subsequent formation of nitrate species in the dark on TiO2 nanoparticles exhibiting different morphologies: An in-situ FTIR study
Adsorption of NO2 and subsequent formation of nitrate species in the dark on TiO2 nanoparticles exhibiting different morphologies: An in-situ FTIR study
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DOI：
10.1016/j.colsurfa.2021.127058
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发表时间：
2021-10
期刊：
影响因子：
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通讯作者：
A. Mahmood;Xiao Wang;Xiaofeng Xie;Jing Sun
中科院分区：
文献类型：
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作者：
A. Mahmood;Xiao Wang;Xiaofeng Xie;Jing Sun
氮氧化物（NOx）是主要的空气污染物之一，它是造成光化学烟雾和霾形成的原因，并可导致酸雨。选择性催化还原（SCR）技术是一种很有前途的控制各种固定和移动的源NOx排放的方法。NO2的化学吸附被认为是该多相催化过程的关键步骤。在此，采用原位红外光谱法，以NO2为原料气，在黑暗条件下研究了不同形貌的TiO 2纳米颗粒（TiO 2三角形、TiO 2纳米线、TiO 2纳米立方体）对硝酸根的吸附和形成. N2 O 4的形成是第一步，一旦TiO 2纳米粒子进行NO2吸附，这是同时转化为其他硝酸盐物种通过分子内的反硝化反应。然而，具有不同形态的TiO 2纳米颗粒显示出不同的趋势，对各种硝酸盐物种的稳定性和形成。特别地，仅在TiO 2纳米线和TiO 2纳米立方体（10mL_HF/40 h）中观察到NO+的形成。同时，在TiO 2三角形纳米颗粒、TiO 2纳米立方体（4mL_HF/24 h）和TiO 2纳米立方体（10mL_HF/24 h）中均检测到NO2的存在，并观察到不同NO3-物种的形成，包括单齿、双齿和桥连NO3-（m-，B-，br-NO3-）。该研究为选择性催化还原技术中TiO 2基载体的改性提供了有价值的信息。
Nitrogen oxides (NOx) are among the major air pollutants, which are responsible for the photochemical smog and haze formation and can cause acid rain. The selective catalytic reduction (SCR) process is a promising method to control the NOxemission from various stationery and mobile resources. The chemisorption of NO2is regarded as the crucial step in this heterogeneous catalytic process. Here, the adsorption and formation of nitrate species on TiO2nanoparticles (NPs) with different morphologies, designated as TiO2trigonal, TiO2nanowires, TiO2nanocubes was examined in the dark using an in-situ FTIR spectroscopy, under NO2as the feeding gas. The N2O4formation is the initial step as soon as TiO2NPs are subjected to NO2adsorption, that is simultaneously transformed into other nitrate species via intramolecular disproportionation reaction. However, TiO2NPs with different morphologies displayed a distinguished trend towards the stability and formation of various nitrate species. In particular, formation of NO+was noticed only in TiO2nanowires and TiO2nanocubes (10mL_HF/40 h). Also, NO2was detected in TiO2trigonal shaped NPs, TiO2nanocubes (4mL_HF/24 h), and TiO2nanocubes (10mL_HF/24 h).The formation of different NO3-species, including monodentate, bidentate, and bridged NO3-(m-,b-,br-NO3-) were also observed. This study provides valuable information to modify the TiO2-based supports for the selective catalytic reduction technology.