Optimal Geometrical Configuration of Cobalt Cations in Spinel Oxides to Promote Oxygen Evolution Reaction.,Angewandte Chemie International Edition

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Optimal Geometrical Configuration of Cobalt Cations in Spinel Oxides to Promote Oxygen Evolution Reaction.
Angewandte Chemie International Edition ( IF 16.1 ) Pub Date : 2019-12-27 , DOI: 10.1002/anie.201914245
Zhijuan Liu _{1,

2} , Guangjin Wang ₃ , Xiaoyan Zhu ₁ , Yanyong Wang ₁ , Yuqin Zou ₁ , Shuangquan Zang ₂ , Shuangyin Wang ₁

Affiliation

MgCo2 O4 , CoCr2 O4 , and Co2 TiO4 were selected, where only Co3+ in the center of octahedron (Oh), Co2+ in the center of tetrahedron (Td), and Co2+ in the center of Oh, can be active sites for the oxygen evolution reaction (OER). Co3+ (Oh) sites are the best geometrical configuration for OER. Co2+ (Oh) sites exhibit better activity than Co2+ (Td). Calculations demonstrate the conversion of O* into OOH* is the rate-determining step for Co3+ (Oh) and Co2+ (Td). For Co2+ (Oh), it is thermodynamically favorable for the formation of OOH* but difficult for the desorption of O2 . Co3+ (Oh) needs to increase the lowest Gibbs free energy over Co2+ (Oh) and Co2+ (Td), which contributes to the best activity. The coexistence of Co3+ (Oh) and Co2+ (Td) in Co3 O4 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.

中文翻译：

尖晶石氧化物中钴阳离子的最佳几何构型，以促进氧释放反应。

选择了MgCo2 O4，CoCr2 O4和Co2 TiO4，其中只有八面体（Oh）中心的Co3 +，四面体（Td）中心的Co2 +和Oh中心的Co2 +是氧释放的活性位点反应（OER）。Co3 +（Oh）站点是OER的最佳几何构型。Co2 +（Oh）位点显示出比Co2 +（Td）更好的活性。计算表明，O *转化为OOH *是确定Co3 +（Oh）和Co2 +（Td）的速率的步骤。对于Co2 +（Oh），在热力学上有利于OOH *的形成，但对O2的解吸却很困难。与Co2 +（Oh）和Co2 +（Td）相比，Co3 +（Oh）需要增加最低的吉布斯自由能，这有助于实现最佳活性。Co3 O4中Co3 +（Oh）和Co2 +（Td）的共存可促进OOH *的形成并降低自由能垒。

更新日期：2020-01-31

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