Theoretical insight into oxidation catalysis of chromite spinel MCr2O4 (M = Mg, Co, Cu, and Zn): Volcano plot for oxygen-vacancy formation and catalytic activity

Zhao, Peng; Ehara, Masahiro; Satsuma, Atsushi; Sakaki, Shigeyoshi

doi:10.1016/j.jcat.2020.11.006

Cited by 13 publications

(14 citation statements)

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“…49 Considering that the energy difference is tiny and reaction temperature is much higher than room temperature, the ferromagnetic state was employed in previous theoretical studies of catalytic reactions by ZnCr 2 O 4 for easier calculation. 48,49,67 In accordance with those works, 48,49,67 the ferromagnetic state was employed in this work.…”

Section: Computational Details and Modelsmentioning

confidence: 90%

“…We selected Cu and Co for the metal-dopant because these metal elements are expected to accelerate O V formation, as discussed in the Introduction. 48 Here, we need to mention that this modeling differs slightly from the real metaldoped ZnCr 2 O 4 because some of the surface metal atoms would be replaced with the metal-dopant element but the others remain without exchange with the metal-dopant element when the amount of metal-dopant is small. In other words, the effect by metal-doping of this model would be larger than that of a more realistic model.…”

Section: Computational Details and Modelsmentioning

confidence: 99%

“…Recently, the lowest energy surface termination of ZnCr 2 O 4 (111) was reported. 48 In this work, we used the slab model bearing the same lowest energy surface termination. A p(2 × 2) slab model with inversion symmetry was used with a thickness of about 9.0 Å, where the vacuum region was taken to be 15 Å.…”

Section: Computational Details and Modelsmentioning

confidence: 99%

“…Then, the *CO reacts with O latt to yield CO 2 and one O V site (E a = 1.00 eV) on ZnCr 2 O 4 (111). 48 O 2 adsorption occurs at the O V site, and its O t atom reacts with the two remaining *H atoms to yield H 2 O (29 → 33 step in Figure 5b; E a = 0.06 eV for TS_30/31 and 0.02 eV for TS_32/ 33). In this process, the largest E a (1.66 eV) is needed at TS_21/22.…”

Section: Computational Details and Modelsmentioning

confidence: 99%

“…47 A recent theoretical work on CO oxidation catalysis of MCr 2 O 4 (M = Mg, Co, Cu, and Zn) elucidated that the available oxidation state of M is an important determination factor in the O V formation and a metal element bearing a lower oxidation state such as Cu and Co is favorable for easy O V formation. 48 Therefore, we address the last open question: if Cu-and Co-dopants are effective to accelerate the surface O V formation and improve the catalytic activity.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Study of the Propene Combustion Catalysis of Chromite Spinels: Reaction Mechanism and Relation between the Activity and Electronic Structure of Spinels

et al. 2021

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Oxides of base-metal elements play an important role as catalysts in alkene combustion, but correct knowledge of the reaction mechanism and determination factors for activity remains elusive. Herein, we report a systematic study of propene combustion catalyzed by ZnCr2O4(111) as one example using DFT + U calculations. The combustion occurs through three parallel reaction pathways starting from C–H σ-bond cleavage. In each pathway, acetate, carbonate, or formate is formed as a key intermediate, which is consistent with the experimental detection of several different kinds of intermediates in propene combustion. Effects of tetrahedral metal (MTd) and octahedral metal (MOh) atoms on the catalytic activity are discussed by comparing propene combustion by MgCr2O4(111), Cu-doped ZnCr2O4(111) (named Zn1 – x Cu x Cr2O4(111)), and Co-doped ZnCr2O4(111) (named ZnCr2 – x Co x O4(111)) with that by ZnCr2O4(111). Catalytic activity increases in the order MgCr2O4(111) < Zn1 – x Cu x Cr2O4(111) < ZnCr2O4(111) < ZnCr2 – x Co x O4(111). The higher activity of ZnCr2O4(111) than that of MgCr2O4(111) agrees with the experimental findings. ZnCr2 – x Co x O4(111) is computationally predicted here to be more active than ZnCr2O4(111) which has been experimentally used as a good catalyst. Based on computational findings, a discussion is presented on the relation between the activity and electronic structure of spinels.

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