Reaction Mechanisms for CO Catalytic Oxidation by N₂O on Fe-Embedded Graphene

Abstract

Catalytic conversion of hazardous gases can solve many of the environmental problems caused by them. We performed a density functional theory (DFT) study with the Perdew−Burke−Ernzerhof (PBE) functional to investigate the CO oxidation by using N 2 O as an oxidizing agent over an iron-embedded graphene (Fe-Graphene) catalyst. The N 2 O molecule was first decomposed on the Fe site yielding the N 2 molecule and an Fe−O intermediate, which was an active species for the CO oxidation. The activation energy for the N 2 O decomposition step was predicted to be 8 kcal/mol. According to the population analysis, the graphene acted as both the electron withdrawing and donating support to assist the charge transfer between the Fe atom and the probe molecules, which are important for the reaction. The reaction was found to be less facile when the Fe site was first covered by the CO which has a higher adsorption energy than that of the N 2 O (−10.0 vs −33.6 kcal/mol). The reaction proceeded via a concerted transition structure and required an activation energy of 19.2 kcal/mol when the CO was prior adsorbed. Thus, control of the adsorbing molecules over Fe-Graphene might be a key factor for the activity of the catalyst. With the higher catalytic activities of Fe-embedded graphene compared to other typical catalysts, this may open new avenues in searching for oxidation of CO at an economical cost.

Theoretical study of methane adsorption and C─H bond activation over Fe‐embedded graphene: Effect of external electric field

“…The positive EF made the structural change of the C─H bond becomes more an earlier transition state. This result agreed with a previous theoretical study of the methane C─H bond dissociation on Au‐supporting zeolites using the M06‐L/6‐31G** level of theory . The complexation of the coordinated CH 3 group and H atom on Fe site is 5.7 kcal/mol endothermic for the system without the EF.…”

“…The superior adsorption properties of Fe‐graphene for several small molecules such as formaldehyde, hydrogen sulfide, carbon monoxide have made it as a promising material for the applications of gas adsorptions and gas sensors . The Fe‐graphene was also used as a catalyst for various reactions for example N 2 O decomposition and CO oxidation . It also had the advantages of being a low‐cost catalyst and low toxicity compared to noble metals.…”

Silicon-coordinated nitrogen-doped graphene as a promising metal-free catalyst for N2O reduction by CO: a theoretical study

“…The calculated reaction energy of N 2 O + CO / N 2 + CO 2 in this work is À3.41 eV. This value is comparable to À3.5 eV reported by theoretical calculations in Siand Fe-doped graphene 15,49 and À3.8 eV of the direct reaction of CO with N 2 O from experiment. 50 The N 2 O reduction and CO oxidation prefer Path 1A with an E a of 0.34 eV and Path 2A with an E a of 0.66 eV.…”

Theoretical investigation for the reaction of N2O with CO catalyzed by Pt-Graphene

“…Along the PES (see Fig. 6), the distance of Wannakao et al [35] have reported the reaction mechanisms for CO catalytic oxidation by N 2 O on Fe-embedded graphene. Compared with the two catalysts, Fe-Graphene and Pt-Graphene, we find that the N 2 O is more likely to adsorb on the Fe-Graphene (−10.0 vs 4.89 kcal/mol ), but the barrier energies of N-O scission is higher than the PtGraphene (8.0 vs 4.30 kcal/mol), which means the catalytic activity of Pt-Graphene is better than the Fe-Graphene for the mechanism of adsorption of N 2 O followed by CO. As for the other mechanism of adsorption of CO followed by N 2 O, both the adsorption energy (CO-Fe-Graphnene: E ads = −33.7 kcal/ mol; CO-Pt-Graphene: E ads = −31.67 kcal/mol) and barrier energy (19.2 [35] vs 20.28 kcal/mol) are nearly the same on the two catalysts, while the barrier energy is much higher than the former mechanism.…”