Dark NO2 Reduction on a Graphene Surface with Implications for Soot Aging and HONO Formation,Environmental Science & Technology

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Dark NO2 Reduction on a Graphene Surface with Implications for Soot Aging and HONO Formation
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2024-09-10 , DOI: 10.1021/acs.est.4c03406
Peng Zhang _{1,

2} , Hao Li ₁ , Shuying Wang ₁ , Biwu Chu _{1,

2,

3} , Tianzeng Chen _{1,

2} , Qingxin Ma _{1,

2} , Yonghong Wang _{1,

2} , Yunbo Yu _{1,

2,

3} , Hong He _{1,

2,

3}

Affiliation

Soot, primarily composed of elemental carbon (EC) and organic carbon (OC), is ubiquitous in PM_2.5. In the atmosphere, the heterogeneous interaction between NO₂ and soot is not only an important pathway driving soot aging but also of central importance to nitrous acid (HONO) formation. It is commonly believed that the surface redox reaction between reductive OC and NO₂ dominates the night aging of soot and the conversion of NO₂ to HONO. However, completely differing from the currently popular explanation, we find here that the redox reaction between EC and NO₂ can also drive the conversion of NO₂ to HONO during soot aging. By combining in situ experiments with density functional theory (DFT) calculations, we proposed that the surface carbon vacancy defects on graphite/graphene-like EC should be a type of potential primary adsorption and reactive sites inducing the heterogeneous reduction of NO₂. We suggested a new mechanism that NO₂ is reduced to form HONO on surface vacancy defects through the splitting of H₂O molecules, and the carbon atoms adjacent to surface vacancy are simultaneously oxidized to form hydroxyl-functionalized EC. This novel finding provides insights into the chemical mechanism driving the NO₂-to-HONO conversion and rapid soot aging, which expands our knowledge of the heterogeneous chemistry of soot in the atmosphere.

中文翻译：

石墨烯表面的暗 NO2 还原对烟灰老化和 HONO 形成的影响

烟灰主要由元素碳 (EC) 和有机碳 (OC) 组成，在 PM _2.5中普遍存在。在大气中，NO ₂和烟灰之间的异质相互作用不仅是驱动烟灰老化的重要途径，而且对于亚硝酸（HONO）的形成也至关重要。人们普遍认为，还原性OC和NO ₂之间的表面氧化还原反应主导着烟灰的夜间老化和NO ₂向HONO的转化。然而，与目前流行的解释完全不同，我们在这里发现EC和NO ₂之间的氧化还原反应也可以在烟灰老化过程中驱动NO ₂转化为HONO。通过将原位实验与密度泛函理论（DFT）计算相结合，我们提出石墨/类石墨烯EC的表面碳空位缺陷应该是一种潜在的初级吸附和诱导NO ₂异质还原的反应位点。我们提出了一种新的机制：通过H ₂ O分子的分裂，NO ₂在表面空位缺陷上被还原形成HONO，同时与表面空位相邻的碳原子被氧化形成羟基功能化的EC。这一新发现为驱动NO ₂转化为HONO 和快速烟灰老化的化学机制提供了见解，从而扩展了我们对大气中烟灰非均相化学的认识。

更新日期：2024-09-10

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