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Optimal Geometrical Configuration of Cobalt Cations in Spinel Oxides to Promote Oxygen Evolution Reaction
Author(s) -
Liu Zhijuan,
Wang Guangjin,
Zhu Xiaoyan,
Wang Yanyong,
Zou Yuqin,
Zang Shuangquan,
Wang Shuangyin
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201914245
Subject(s) - cobalt , oxygen evolution , octahedron , chemistry , spinel , oxygen , tetrahedron , desorption , catalysis , inorganic chemistry , crystallography , materials science , crystal structure , electrochemistry , adsorption , organic chemistry , electrode , metallurgy
MgCo 2 O 4 , CoCr 2 O 4 , and Co 2 TiO 4 were selected, where only Co 3+ in the center of octahedron (Oh), Co 2+ in the center of tetrahedron (Td), and Co 2+ in the center of Oh, can be active sites for the oxygen evolution reaction (OER). Co 3+ (Oh) sites are the best geometrical configuration for OER. Co 2+ (Oh) sites exhibit better activity than Co 2+ (Td). Calculations demonstrate the conversion of O* into OOH* is the rate‐determining step for Co 3+ (Oh) and Co 2+ (Td). For Co 2+ (Oh), it is thermodynamically favorable for the formation of OOH* but difficult for the desorption of O 2 . Co 3+ (Oh) needs to increase the lowest Gibbs free energy over Co 2+ (Oh) and Co 2+ (Td), which contributes to the best activity. The coexistence of Co 3+ (Oh) and Co 2+ (Td) in Co 3 O 4 can promote the formation of OOH* and decrease the free‐energy barrier. This work screens out the optimal geometrical configuration of cobalt cations for OER and gives a valuable principle to design efficient electrocatalysts.