Particle Size Effects in Stoichiometric Methane Combustion: Structure–Activity Relationship of Pd Catalyst Supported on Gamma-Alumina,ACS Catalysis

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Particle Size Effects in Stoichiometric Methane Combustion: Structure–Activity Relationship of Pd Catalyst Supported on Gamma-Alumina
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-08-12 , DOI: 10.1021/acscatal.0c03111
Jianjun Chen ₁ , Jiawei Zhong ₂ , Yang Wu ₁ , Wei Hu ₃ , Pengfei Qu ₄ , Xin Xiao ₄ , Guochen Zhang ₄ , Xi Liu ₄ , Yi Jiao ₁ , Lin Zhong ₄ , Yaoqiang Chen _{1,

5}

Affiliation

It is an urgent desire to shed insight into the structure–activity relationship of catalysts for stoichiometric methane combustion, a very important reaction in energy utilization and environmental governance. Here, we report variedly sized Pd nanoparticles (NPs) (2.1–10.4 nm) on gamma-alumina by a one-step colloid synthesis method for stoichiometric methane combustion. The results of structural analysis based on transmission electron microscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy show that, with increasing size, Pd NPs evolve their shape from irregular to spherical-like structure along with a progressively decreased fraction of Pd corner sites. Moreover, the intrinsic catalytic activity (turnover frequency) of Pd NPs for methane combustion monotonously decreases by about 6-fold when the size of Pd NPs increases from 2.1 to 10.4 nm, suggestive of a protuberant size-dependent activity of Pd catalyst in this reaction. Further confirmed by the potential energy profiles of the rate-determining step in the reaction from density functional theory calculations, the methane molecule is much easier to be activated on corner sites than on the other sites (i.e., edge and terrace sites) over Pd NPs. This work elucidates the origin of size-dependent activity of Pd catalysts via an investigation on their surface structure and could help to engineer highly efficient catalysts for this reaction.

中文翻译：

化学计量甲烷燃烧中的颗粒尺寸效应：γ-氧化铝负载的Pd催化剂的结构-活性关系

迫切需要深入了解化学计量甲烷燃烧催化剂的结构与活性之间的关系，这是能源利用和环境治理中非常重要的反应。在这里，我们通过化学计量甲烷燃烧的一步胶体合成方法报告了在γ-氧化铝上尺寸不同的钯纳米颗粒（NPs）（2.1-10.4 nm）。基于透射电子显微镜和原位漫反射红外傅立叶变换光谱的结构分析结果表明，随着尺寸的增加，Pd NPs的形状从不规则结构演变为球形结构，并且Pd角位点的比例逐渐降低。此外，当Pd NPs的尺寸从2.1 nm增加到10.4 nm时，Pd NPs的甲烷燃烧固有催化活性（转换频率）单调降低约6倍，这表明Pd催化剂在此反应中具有突出的尺寸依赖性。根据密度泛函理论计算，反应中速率确定步骤的势能图进一步证实，甲烷分子在角点位点比在Pd NP上的其他位点（即边缘位点和平台位点）更容易被激活。这项工作通过对Pd催化剂表面结构的研究，阐明了Pd催化剂的尺寸依赖性活性的起源，并可能有助于设计用于该反应的高效催化剂。根据密度泛函理论计算，反应中速率确定步骤的势能图进一步证实，甲烷分子在角点位点比在Pd NP上的其他位点（即边缘位点和平台位点）更容易被激活。这项工作通过对Pd催化剂表面结构的研究，阐明了Pd催化剂的尺寸依赖性活性的起源，并可能有助于设计用于该反应的高效催化剂。根据密度泛函理论计算，反应中速率确定步骤的势能图进一步证实，甲烷分子在角点位点比在Pd NP上的其他位点（即边缘位点和平台位点）更容易被激活。这项工作通过对Pd催化剂表面结构的研究，阐明了Pd催化剂的尺寸依赖性活性的起源，并可能有助于设计用于该反应的高效催化剂。

更新日期：2020-09-20

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