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首页> 外文期刊>Journal of Materials Chemistry, A. Materials for energy and sustainability >Novel hydrogen chemisorption properties of amorphous ceramic compounds consisting of p-block elements: exploring Lewis acid-base Al-N pair sites formed in situ within polymer-derived silicon-aluminum-nitrogen-based systems
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Novel hydrogen chemisorption properties of amorphous ceramic compounds consisting of p-block elements: exploring Lewis acid-base Al-N pair sites formed in situ within polymer-derived silicon-aluminum-nitrogen-based systems

机译：由P嵌段元件组成的非晶陶瓷化合物的新型氢化学化学性能：在聚合物衍生的硅 - 铝 - 氮基体系中探索石油酸碱基础Al-N对部位

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摘要

This paper reports the relationship between the H-2 chemisorption properties and reversible structural reorientation of the possible active sites around Al formed in situ within polymer-derived ceramics (PDCs) based on an amorphous silicon-aluminum-nitrogen (Si-Al-N) system. Al-modified polysilazane, as a ceramic precursor, was first pyrolyzed at 1000 degrees C under flowing ammonia to generate a Si-Al-N-based ceramic. XRD and HRTEM analyses confirmed the amorphous state of the titled ceramics. N-2 adsorption-desorption isotherm measurements and HAADF-STEM observation of amorphous SiAlN indicated that Al-incorporation in the early step of the process led to the generation of micro/mesoporosity in the amorphous ceramic with nanopores of 1 to 4 nm in size. XPS and pyridine sorption infra-red spectroscopy analyses revealed the in situ formation of Lewis acidic Al sites within the amorphous Si-Al-N surface network. As a result, the Si-Al-N compound was highly moisture sensitive. Then, to investigate the intrinsic properties of the highly reactive Al sites, the Si-Al-N compound was pretreated at 400-800 degrees C under an inert atmosphere. Temperature-programmed-desorption (TPD)-mass spectroscopy analysis of the pre-treated sample after H-2 treatment above 100 degrees C resulted in the detection of a broad H-2 desorption peak at around 100 to 350 degrees C. The H-2 desorption peak intensity apparently increased when H-2 treatment was performed at 150 degrees C, and the activation energy for H-2 desorption was determined to be 44 kJ mol(-1). Al-27 MAS NMR spectroscopic analysis for the pre-treated sample showed reversible local structure reorientation around reactive Al nuclei, and formation and deformation of 5-fold coordinated Al by H-2 chemisorption and desorption, respectively. In addition, the CO2 hydrogenation reaction on the pre-treated sample was successfully demonstrated by TPD measurements after exposure to a mixed gas of H-2 and CO2 with a 4 : 1 ratio at 400 degrees C. These results suggest that highly distorted 4-fold coordinated Al serves as a Lewis acid-base Al-N pair site to promote H-2 chemisorption at T > 100 degrees C followed by formation of a hydrogenated 5-coordinated Al unit where CO2 hydrogenation proceeds at T = 400 degrees C.
机译：本文报道了基于非晶硅铝氮（Si-Al-N）体系的聚合物衍生陶瓷（PDC）中原位形成的铝周围可能的活性中心的H-2化学吸附性能与可逆结构再取向之间的关系。铝改性聚硅氮烷作为一种陶瓷前驱体，首先在1000℃下在流动的氨水下热解生成Si-Al-N基陶瓷。XRD和HRTEM分析证实了标题陶瓷的非晶态。N-2吸附-解吸等温线测量和非晶态SiAlN的HAADF-STEM观察表明，在该过程的早期阶段，铝的掺入导致非晶态陶瓷中产生微米/中孔，纳米孔尺寸为1至4 nm。XPS和吡啶吸附红外光谱分析表明，在非晶态Si-Al-N表面网络中原位形成了路易斯酸性铝位。因此，Si-Al-N化合物对水分高度敏感。然后，为了研究高反应性Al位的固有性质，在400-800℃的惰性气氛下对Si-Al-N化合物进行预处理。程序升温脱附（TPD）-在100℃以上进行H-2处理后，对预处理样品进行质谱分析，发现在100至350℃左右有一个宽的H-2脱附峰。在150℃进行H-2处理时，H-2脱附峰强度明显增加，H-2解吸的活化能为44 kJ mol（-1）。预处理样品的Al-27 MAS NMR光谱分析表明，反应性Al核周围存在可逆的局部结构重取向，以及通过H-2化学吸附和解吸分别形成和变形的5倍配位Al。此外在400℃下暴露于H-2和CO2的混合气体（比例为4:1）后，TPD测量成功证明了预处理样品上的CO2加氢反应。这些结果表明，高度扭曲的4倍配位Al作为Lewis酸碱Al-N对位点，促进H-2在T>100℃下的化学吸附，然后形成氢化物5-配位铝单元，其中CO2加氢在T=400℃下进行。

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  • 作者

    Tada Shotaro; Asakuma Norifumi; Ando Shiori; Asaka Toru; Daiko Yusuke; Honda Sawao; Haneda Masaaki; Bernard Samuel; Riedel Ralf; Iwamoto Yuji;

  • 作者单位

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

    Univ Limoges CNRS IRCER UMR 7315 F-87000 Limoges France;

    Tech Univ Darmstadt Inst Mat Wissensch Otto Berndt Str 3 D-64287 Darmstadt Germany;

    Nagoya Inst Technol Grad Sch Engn Dept Life Sci &

    Appl Chem Showa Ku Gokiso Cho Nagoya Aichi 4668555 Japan;

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  • 正文语种 eng
  • 中图分类 工程材料学;
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