Unraveling the Origin of Ceria Activity in Water–Gas Shift by First-Principles Microkinetic Modeling,The Journal of Physical Chemistry C

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Unraveling the Origin of Ceria Activity in Water–Gas Shift by First-Principles Microkinetic Modeling
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-03-31 , DOI: 10.1021/acs.jpcc.0c00229
Agustín Salcedo _{1,

2} , Beatriz Irigoyen _{1,

2}

Affiliation

Water–gas shift (WGS) is a well-known reaction for production and purification of hydrogen from synthesis gas. Transition metals supported on ceria (CeO₂) have received much attention as single-step catalysts for the low-temperature WGS reaction. The intrinsic WGS activity of the ceria support indicates that it might play an essential role in the catalytic process. However, there is still no consensus on the governing reaction mechanism at mild conditions. Thus, in this work self-consistent periodic density functional theory and microkinetic calculations were performed to investigate redox, formate-mediated, and carboxyl-mediated pathways on the CeO₂(111) surface. Binding energies of reactants (H₂O and CO), intermediates (OH, formate, and carboxyl), and products (CO₂ and H₂) were calculated, together with energy barriers associated with possible elementary reaction steps. These results were used as input in a mean-field microkinetic model. The analysis of degrees of rate control from microkinetic calculations shows the prevalence of a combined redox-associative route for WGS on pure ceria. Overall, these results provide insight into the WGS reaction on ceria and can contribute to experimental research of catalytic systems for low-temperature WGS.

中文翻译：

通过第一性原理微动力学模型揭示水煤气转换中二氧化铈活性的起源

水煤气变换（WGS）是众所周知的反应，用于从合成气生产和纯化氢气。负载在二氧化铈上的过渡金属（CeO ₂）作为低温WGS反应的一步催化剂受到了广泛的关注。二氧化铈载体的固有WGS活性表明它可能在催化过程中起重要作用。然而，对于在温和条件下的反应机理尚无共识。因此，在这项工作中，进行了自洽的周期性密度泛函理论和微动力学计算，以研究CeO ₂（111）表面上的氧化还原，甲酸介导和羧基介导的途径。反应物的结合能（H ₂O和CO），中间体（OH，甲酸酯和羧基）和产物（CO ₂和H ₂），以及与可能的基本反应步骤相关的能垒。这些结果用作平均场微动力学模型的输入。通过微动力学计算对速率控制程度的分析表明，纯氧化铈上WGS的氧化还原-缔合结合途径普遍存在。总的来说，这些结果提供了关于氧化铈在WGS上反应的见解，并有助于低温WGS催化体系的实验研究。

更新日期：2020-04-01

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