First Principles Study on the CO Oxidation on Mn-Embedded Divacancy Graphene.

Quanguo Jiang,Yuping Wu,Jianfeng Zhang,Haiyan He,Huajie Huang,Zhimin Ao

doi:10.3389/fchem.2018.00187

Quanguo Jiang, Yuping Wu + Show 4 more

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https://doi.org/10.3389/fchem.2018.00187

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Abstract

The CO oxidation mechanism on graphene with divacancy (DG) embedded with transition metal from Sc to Zn has been studied by using first principles calculations. The results indicate that O2 molecule is preferentially adsorbed on Sc, Ti, V, Cr, Mn, and Fe-DG, which can avoid the CO poisoning problem that many catalysts facing and is beneficial to the CO oxidation progress. Further study indicates that Mn-DG shows the best catalytic properties for CO oxidation with consideration of both Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) oxidation mechanisms. Along the ER mechanism, the reaction energy barrier for the first step (CO free + O2 pre-adsorbed → OOCO) is 0.96 eV. Along the LH mechanism, the energy barrier for the rate limiting step (CO adsorbed + O2 adsorbed → OOCO) is only 0.41 eV, indicating that the CO oxidation on Mn-DG will occur along LH mechanism. The Hirshfeld charge distributions of O2 and CO molecules is tuned by the embedded Mn atom, and the charge transfer from the embedded Mn atom to the adsorbed molecules plays an important role for the CO oxidation. The result shows that the Mn-embedded divacancy graphene is a noble-metal free and efficient catalyst for CO oxidation at low temperature.

Highlights

Carbon monoxide (CO) is colorless, tasteless and toxic in air, while oxidation of CO is an efficient way to eliminate of the air pollutant (Xie et al, 2009)
Based on the literature results in the introduction section, it is expected that transition-metal-embedded divacancy graphene (TM-DG) could exhibit excellent catalytic behaviors for CO oxidation, similar to the cases of graphene with single vacancy systems
To comprehensively understanding the adsorption behaviors of O2 and CO molecules on transition metal decorated divacancy graphene, the adsorption energies of O2 and CO, as well as the co-adsorption energy of O2 and CO molecules on TM-DG are shown in Figure 1, where we can see that the adsorption energy of O2 molecule is larger than that of CO molecule on TM-DG, while the adsorption energy of CO molecule is larger than that of O2 molecule on TM-DG

Summary

Introduction

Carbon monoxide (CO) is colorless, tasteless and toxic in air, while oxidation of CO is an efficient way to eliminate of the air pollutant (Xie et al, 2009). Noble metal clusters on supports are further studied to decrease the reaction barriers for CO oxidation (Tang et al, 2015; Ma et al, 2016; Wang et al, 2016; Ali et al, 2017; Chen et al, 2017).

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