Role of Oxygen Vacancy Defects in the Electrocatalytic Activity of Substoichiometric Molybdenum Oxide

Mesoporous α-MoO3–x combined with poly­(diallyldimethylammonium chloride)–functionalized reduced graphene oxide (PDDA–rGO) is introduced as an inexpensive and efficient oxygen reduction reaction (ORR) catalyst. The mesoporous catalysts are wrapped by conductive rGO sheets via an electrostatic intera...

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Veröffentlicht in:Journal of physical chemistry. C 2018-08, Vol.122 (32), p.18212-18222
Hauptverfasser: Kashfi-Sadabad, Raana, Yazdani, Sajad, Huan, Tran Doan, Cai, Zhao, Pettes, Michael Thompson
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Sprache:eng
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Zusammenfassung:Mesoporous α-MoO3–x combined with poly­(diallyldimethylammonium chloride)–functionalized reduced graphene oxide (PDDA–rGO) is introduced as an inexpensive and efficient oxygen reduction reaction (ORR) catalyst. The mesoporous catalysts are wrapped by conductive rGO sheets via an electrostatic interaction induced by a PDDA polyelectrolyte. The thermal interaction of PDDA with MoO3 efficiently reduces the metal oxide to MoO3–x at 400–600 °C, creating a surface oxygen vacancy. Through a combination of density functional theory and experiments, the role of the surface oxygen vacancy sites in the ORR activity of MoO3–x is identified. For the first time, all the energy barriers against ORR are calculated at each step for MoO3 with no oxygen vacancies and MoO3–x with surface oxygen vacancies. It is shown that the presence of an M o 4 + ‐ v O • • oxygen vacancy site on the surface significantly reduces the energy barriers against ORR in the reaction pathways. An overpotential of 0.86 V (vs a reversible hydrogen electrode) with excellent electrochemical stability was obtained with the newly designed catalyst, with only a 9% decrease in the activity after ∼17 h. These results offer a new paradigm in the defect engineering of metal oxides with a potential for the synthesis of stable and active noble metal-free ORR electrocatalysts.
ISSN:1932-7447
1932-7455
DOI:10.1021/acs.jpcc.8b03536