On the Surface Acid–Base Properties of Amorphous and Crystalline Mg2SiO4 as Probed by Adsorbed CO, CO2, and CD3CN,ACS Earth and Space Chemistry

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On the Surface Acid–Base Properties of Amorphous and Crystalline Mg2SiO4 as Probed by Adsorbed CO, CO2, and CD3CN
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2020-02-25 , DOI: 10.1021/acsearthspacechem.9b00271
Matteo Signorile ₁ , Lorenzo Zamirri ₁ , Akira Tsuchiyama _{2,

3} , Piero Ugliengo ₁ , Francesca Bonino ₁ , Gianmario Martra ₁

Affiliation

In this work, we characterize the surface sites of Mg₂SiO₄, a main constituent of dust grains from the interstellar medium/protoplanetary disks, by using infrared (IR) spectroscopy of adsorbed CO, CO₂, and CD₃CN probe molecules. With the aid of atomistic models from computer simulations, the acid–base properties of the Mg₂SiO₄ surface, as inferred by IR spectroscopy, are discussed as a function of each of two structures, amorphous versus crystalline, as well as that of the morphology of the particles. We found that, while the Lewis acidity of exposed cations (Mg²⁺) is almost independent of the amorphous or crystalline nature of the material, exposed oxygen ions on the other hand are dramatically different in terms of basicity in their crystalline and amorphous phases. Indeed, reactivity toward the CD₃CN molecule only occurs in the amorphous Mg₂SiO₄ particles because of the strong Lewis basicity of the O^2–/OH^– ions.

中文翻译：

吸附CO，CO ₂和CD ₃ CN探测非晶态和结晶态Mg ₂ SiO ₄的表面酸碱性质

在这项工作中，我们通过使用吸附的CO，CO ₂和CD ₃ CN探针分子的红外光谱来表征Mg ₂ SiO ₄的表面位置，Mg ₂ SiO ₄是星际中/原行星盘上尘埃颗粒的主要成分。借助计算机模拟的原子模型，讨论了红外光谱推断的Mg ₂ SiO ₄表面的酸碱性质，它是两种结构（非晶态与结晶态）以及非晶态与结晶态的函数。颗粒的形态。我们发现，尽管暴露阳离子的路易斯酸度（Mg ²⁺）几乎与材料的非晶态或晶体性质无关，另一方面，暴露的氧离子在其晶态和非晶态的碱度方面有很大不同。实际上，朝向CD反应₃ CN分子仅发生在无定形的Mg ₂的SiO ₄，因为将O的强路易斯碱性的粒子^2- / OH ^-离子。

更新日期：2020-02-25

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