Anchoring highly dispersed metal nanoparticles by strong electrostatic adsorption (SEA) on a dealuminated beta zeolite for catalysis
Anchoring highly dispersed metal nanoparticles by strong electrostatic adsorption (SEA) on a dealuminated beta zeolite for catalysis
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通过强静电吸附（SEA）将高度分散的金属纳米粒子锚定在脱铝β沸石上用于催化
DOI：
10.1039/d3cy01334k
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发表时间：
2024
影响因子：
5
通讯作者：
Zou R
中科院分区：
文献类型：
--
作者：
Zou R
具有缺陷的沸石可以与适当的合成方案组合，以有利地稳定金属簇和纳米颗粒（NP）。在这项工作中，通过强静电吸附（SEA）合成在富含缺陷的脱铝β（deAl-β）沸石上制备高度分散的Ni NP，这使得负电性deAl-β和阳离子金属氨络合物（例如，Ni（NH3）62+）。直径为1.9 ± 0.2nm的Ni NP在SEA和在500 °C下在H2中还原后形成，并且在CO2甲烷化中显示出良好的活性（即，比反应速率为3.92 × 10−4 mol s−1 gNi−1，甲烷选择性为99.8%（400 °C，GHSV为30 000 mL g−1 h−1）。 用XAFS、原位DRIFTS和DFT等方法对SEA合成过程的机理进行了研究。所制备的Ni催化剂的XAFS（即，未还原的）表明SEA导致Ni前体中阴离子的交换（例如，Cl-和NO3-）形成Ni（OH）2，而原位DRIFTS显示归属于硅烷醇巢的IR谱带信号显著降低（λ 960 cm-1），这可能归因于Ni（OH）2和硅烷醇巢之间通过SEA的强相互作用。DFT计算表明，与中性硅烷醇巢缺陷（高达150 kJ mol−1）相比，金属络合物更强地结合到带电缺陷位点，证实了在SEA合成条件下金属络合物与沸石载体之间增强的相互作用。研究结果为利用富缺陷沸石载体制备高分散金属催化剂提供了新的可能。
Zeolites with defects can be combined with appropriate synthetic protocols to beneficially stabilise metallic clusters and nanoparticles (NPs). In this work, highly dispersed Ni NPs were prepared on a defect-rich dealuminated beta (deAl-beta) zeolite through strong electrostatic adsorption (SEA) synthesis, which enabled strong interactions between the electronegative deAl-beta and cationic metal ammine complexes (e.g., Ni(NH3)62+) via the framework silanol nests. Ni NPs with diameters of 1.9 ± 0.2 nm were formed after SEA and reduction in H2 at 500 °C and showed good activity in CO2 methanation (i.e., specific reaction rate of 3.92 × 10−4 mol s−1 gNi−1 and methane selectivity of 99.8% at 400 °C under GHSV of 30 000 mL g−1 h−1). The mechanism of the SEA synthetic process was elucidated by ex situ XAFS, in situ DRIFTS, and DFT. XAFS of the as-prepared Ni catalysts (i.e., unreduced) indicates that SEA leads to the exchange of anions in Ni precursors (e.g., Cl− and NO3−) to form Ni(OH)2, while in situ DRIFTS of catalyst reduction shows a significant decrease in the signal of IR bands assigned to the silanol nests (at ∼960 cm−1), which could be ascribed to the strong interaction between Ni(OH)2 and silanol nests via SEA. DFT calculations show that metallic complexes bind more strongly to charged defect sites compared to neutral silanol nest defects (up to 150 kJ mol−1), confirming the enhanced interaction between metallic complexes and zeolitic supports under SEA synthesis conditions. The results provide new opportunities for preparing highly dispersed metal catalysts using defect-rich zeolitic carriers for catalysis.