The adsorption and oxidation of SO2 on MgO surface: experimental and DFT calculation studies,Environmental Science: Nano

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The adsorption and oxidation of SO2 on MgO surface: experimental and DFT calculation studies
Environmental Science: Nano ( IF 5.8 ) Pub Date : 2020-02-13 , DOI: 10.1039/c9en01474h
Honghong Wang _{1,

2,

3,

4,

5} , Cheng Zhong _{1,

2,

3,

4,

5} , Qingxin Ma _{1,

2,

3,

4,

5} , Jinzhu Ma _{1,

2,

3,

4,

5} , Hong He _{1,

2,

3,

4,

5}

Affiliation

The heterogeneous oxidation of sulfur dioxide (SO₂) to sulfate on the surface of MgO particles was investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT). The in situ DRIFTS spectra show that the major products of SO₂ adsorption on MgO particles are sulfite, bisulfite and sulfate, while the coexisting NO₂ and O₂ promote the conversion of sulfite/bisulfite into sulfate. DFT calculations show that the main adsorption products of SO₂ on the perfect MgO (001) surface, the hydroxylated MgO (001) surface and the step sites of the MgO (001) surface are sulfite (SO_2,gas + O_lattice → SO_3,ads), bisulfite and sulfate, respectively. The oxidation of sulfite to sulfate was hardly promoted by the presence of O₂ at room temperature, because the process needs to overcome an energy barrier of 0.67 eV. The existence of NO₂ couldn't promote the formation of sulfate, because the direct oxidation of sulfite into sulfate by NO₂ is difficult (ΔE_a = 1.08 eV). However, coexisting NO₂ with O₂ can facilitate the oxidation of SO₂, which illustrates the micro-mechanism of the synergistic effect between SO₂ and NO₂ on MgO. In contrast to sulfite, surface bisulfite formed through the adsorption of SO₂ on surface OH could be oxidized by O₂ or NO₂via barrierless processes. This mechanism highlights the synergistic effects of O₂/NO₂ as well as surface hydroxyl on the heterogeneous oxidation of SO₂ on the MgO surface. Atmospheric implications of the heterogeneous oxidation of SO₂ on MgO under ambient atmosphere are discussed.

中文翻译：

SO2在MgO表面的吸附和氧化：实验和DFT计算研究

利用原位漫反射红外傅里叶变换光谱法（DRIFTS）和密度泛函理论（DFT）研究了MgO颗粒表面二氧化硫（SO ₂）向硫酸盐的非均相氧化。在原位DRIFTS谱图表明，SO的主要产物₂吸附对MgO颗粒是亚硫酸盐，亚硫酸氢盐和硫酸盐，而共存的NO ₂和O ₂促进亚硫酸盐/亚硫酸氢盐的成硫酸盐的转化率。DFT计算表明，在理想的MgO（001）表面，羟基化的MgO（001）表面和MgO（001）表面的台阶处，SO ₂的主要吸附产物为亚硫酸盐（SO ₂+ O_晶格→SO _3，ads），亚硫酸氢盐和硫酸盐。在室温下，O ₂的存在几乎不会促进亚硫酸盐氧化为硫酸盐，因为该过程需要克服0.67 eV的能垒。NO ₂的存在不能促进硫酸盐的形成，因为亚硝酸盐很难被NO ₂直接氧化成硫酸盐（ΔE _a = 1.08 eV）。然而，NO ₂与O ₂共存可以促进SO ₂的氧化，这说明了SO ₂与NO ₂协同作用的微观机制。在MgO上。与亚硫酸盐相反，通过SO ₂吸附在表面OH上形成的表面亚硫酸氢盐可以通过无障碍工艺被O ₂或NO ₂氧化。这种机理突出了O ₂ / NO ₂以及表面羟基对MgO表面SO ₂异相氧化的协同作用。讨论了大气环境下MgO上SO ₂异质氧化的大气影响。

更新日期：2020-02-13

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