Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methane

Alkaline-earth metal oxides with the rocksalt structure, which are simple ionic solids, have attracted attention in attempts to gain fundamental insights into the properties of metal oxides. The surfaces of alkaline-earth metal oxides are considered promising catalysts for the oxidative coupling of...

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Main Authors: Nobutsugu Hamamoto, Takakazu Kawahara, Ryoto Hagiwara, Kohei Matsuo, Kodai Matsukawa, Yoyo Hinuma, Takashi Toyao, Ken-Ichi Shimizu, Takashi Kamachi
Format: Article
Language:English
Published: Taylor & Francis Group 2025-12-01
Series:Science and Technology of Advanced Materials
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Online Access:https://www.tandfonline.com/doi/10.1080/14686996.2024.2435801
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author Nobutsugu Hamamoto
Takakazu Kawahara
Ryoto Hagiwara
Kohei Matsuo
Kodai Matsukawa
Yoyo Hinuma
Takashi Toyao
Ken-Ichi Shimizu
Takashi Kamachi
author_facet Nobutsugu Hamamoto
Takakazu Kawahara
Ryoto Hagiwara
Kohei Matsuo
Kodai Matsukawa
Yoyo Hinuma
Takashi Toyao
Ken-Ichi Shimizu
Takashi Kamachi
author_sort Nobutsugu Hamamoto
collection DOAJ
description Alkaline-earth metal oxides with the rocksalt structure, which are simple ionic solids, have attracted attention in attempts to gain fundamental insights into the properties of metal oxides. The surfaces of alkaline-earth metal oxides are considered promising catalysts for the oxidative coupling of methane (OCM); however, the development of such catalysts remains a central research topic. In this paper, we performed first-principles calculations to investigate the ability of four alkaline-earth metal oxides (MgO, CaO, SrO, and BaO) to catalyze the OCM. We adopted five types of surfaces of rocksalt phases as research targets: the (100), (110), stepped (100), oxygen-terminated octopolar (111), and metal-terminated octopolar (111) surfaces. We found that the formation energy of surface O vacancies is a good descriptor for the adsorption energy of a H atom and a methyl radical. The energies related to the OCM mechanism show that, compared with the most stable surface, the minor surfaces better promote the C – H bond cleavage of methane. However, as the trade-off for this advantage, the minor surfaces exhibit increased affinity for the methyl radical. On the basis of this trade-off relationship between properties, we identified several surfaces that we expect to be promising OCM catalysts. Our investigation of the temperature dependence of the Gibbs free energy indicated that, at higher temperatures, the step (100) surface exhibits properties that might benefit the OCM mechanism.
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spelling doaj-art-0ba7ea9ce006450f9cd1165e93e772ae2025-08-20T01:58:38ZengTaylor & Francis GroupScience and Technology of Advanced Materials1468-69961878-55142025-12-0126110.1080/14686996.2024.2435801Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methaneNobutsugu Hamamoto0Takakazu Kawahara1Ryoto Hagiwara2Kohei Matsuo3Kodai Matsukawa4Yoyo Hinuma5Takashi Toyao6Ken-Ichi Shimizu7Takashi Kamachi8Department of Applied Chemistry, Faculty of Engineering, Sanyo-Onoda City University, Sanyo-Onoda, JapanDepartment of Life, Environment and Applied Chemistry, Fukuoka Institute of Technology, Fukuoka, JapanDepartment of Life, Environment and Applied Chemistry, Fukuoka Institute of Technology, Fukuoka, JapanDepartment of Life, Environment and Applied Chemistry, Fukuoka Institute of Technology, Fukuoka, JapanDepartment of Life, Environment and Applied Chemistry, Fukuoka Institute of Technology, Fukuoka, JapanDepartment of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka, JapanInstitute for Catalysis, Hokkaido University, Sapporo, Hokkaido, JapanInstitute for Catalysis, Hokkaido University, Sapporo, Hokkaido, JapanDepartment of Life, Environment and Applied Chemistry, Fukuoka Institute of Technology, Fukuoka, JapanAlkaline-earth metal oxides with the rocksalt structure, which are simple ionic solids, have attracted attention in attempts to gain fundamental insights into the properties of metal oxides. The surfaces of alkaline-earth metal oxides are considered promising catalysts for the oxidative coupling of methane (OCM); however, the development of such catalysts remains a central research topic. In this paper, we performed first-principles calculations to investigate the ability of four alkaline-earth metal oxides (MgO, CaO, SrO, and BaO) to catalyze the OCM. We adopted five types of surfaces of rocksalt phases as research targets: the (100), (110), stepped (100), oxygen-terminated octopolar (111), and metal-terminated octopolar (111) surfaces. We found that the formation energy of surface O vacancies is a good descriptor for the adsorption energy of a H atom and a methyl radical. The energies related to the OCM mechanism show that, compared with the most stable surface, the minor surfaces better promote the C – H bond cleavage of methane. However, as the trade-off for this advantage, the minor surfaces exhibit increased affinity for the methyl radical. On the basis of this trade-off relationship between properties, we identified several surfaces that we expect to be promising OCM catalysts. Our investigation of the temperature dependence of the Gibbs free energy indicated that, at higher temperatures, the step (100) surface exhibits properties that might benefit the OCM mechanism.https://www.tandfonline.com/doi/10.1080/14686996.2024.2435801First-principles calculationalkaline-earth metal oxidestep surfaceoctopolar surface
spellingShingle Nobutsugu Hamamoto
Takakazu Kawahara
Ryoto Hagiwara
Kohei Matsuo
Kodai Matsukawa
Yoyo Hinuma
Takashi Toyao
Ken-Ichi Shimizu
Takashi Kamachi
Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methane
Science and Technology of Advanced Materials
First-principles calculation
alkaline-earth metal oxide
step surface
octopolar surface
title Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methane
title_full Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methane
title_fullStr Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methane
title_full_unstemmed Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methane
title_short Effect of the surface morphology of alkaline-earth metal oxides on the oxidative coupling of methane
title_sort effect of the surface morphology of alkaline earth metal oxides on the oxidative coupling of methane
topic First-principles calculation
alkaline-earth metal oxide
step surface
octopolar surface
url https://www.tandfonline.com/doi/10.1080/14686996.2024.2435801
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