Tailoring the Co 3d-O 2p Covalency in LaCoO3 by Fe Substitution To Promote Oxygen Evolution Reaction
Tailoring the Co 3d-O 2p Covalency in LaCoO3 by Fe Substitution To Promote Oxygen Evolution Reaction
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DOI：
10.1021/acs.chemmater.7b04534
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发表时间：
2017-12-26
影响因子：
8.6
通讯作者：
Xu, Zhichuan J.
中科院分区：
文献类型：
--
作者：
Duan, Yan;Sun, Shengnan;Xu, Zhichuan J.
LaCoO_3是一种在碱性溶液中催化析氧反应(OER)的活性稳定的催化剂。成本较低，是一种潜在的替代贵金属氧化物如IrO2和RuO2的水电解。然而，根据最近对钙钛矿型氧化物OER的理解，其活性仍有提高的空间。在本工作中，在LaCoO_3中引入了Fe替代以提高其OER性能。密度泛函理论(DFT)计算证实，LaCoO_3中铁取代10at%时，Co_3d-O_2p共价性增强是性能提高的主要原因。密度泛函理论计算和超导量子设计磁强计都显示了Co3+的自旋态从一般的低自旋态(LS：T(2g)(6)e(G)(0)，S=0)转变为高自旋态(Fe掺杂10at%)。X射线吸收近边结构(XANES)支持用自旋态转变引起的10at%Fe取代的绝缘体到半金属转变的密度泛函计算。半金属LaCo0.9Fe0.1O3的Co3d态和O2p态的重叠增加，导致共价性增强，提高了OER性能。这一发现为调节氧化物催化剂中金属氧的共价性提供了一条新的途径。
LaCoO3 is an active, stable catalyst in alkaline solution for oxygen evolution reaction (OER). With lower cost, it is a potential alternative to precious metal oxides like IrO2 and RuO2 in water electrolysis. However, room still remains for improving its activity according to recent understandings of OER on perovskite oxides. In this work, Fe substitution has been introduced in LaCoO3 to boost its OER performance. Density function theory (DFT) calculation verified that the enhanced performance originates from the enhanced Co 3d-O 2p covalency with 10 at% Fe substitution in LaCoO3. Both DFT calculations and Superconducting Quantum Design (SQUID) magnetometer (MPMS-XL) showed a Co3+ spin state transition from generally low spin state (LS: t(2g)(6) e(g)(0), S = 0) to a higher spin state with the effect of 10 at% Fe substitution. X-ray absorption near-edge structure (XANES) supports DFT calculations on an insulator to half-metal transition with 10 at% Fe substitution, induced by spin state transition. The half-metallic LaCo0.9Fe0.1O3 possesses increased overlap between Co 3d and O 2p states, which results in enhanced covalency and promoted OER performance. This finding enlightens a new way of tuning the metaloxygen covalency in oxide catalysts for OER.