Tailoring the Co 3d-O 2p Covalency in LaCoO 3 by Fe Substitution To Promote Oxygen Evolution Reaction

作者：Yan Duan, Shengnan Sun, Shibo Xi, Xiao Ren, Ye Zhou, Ganlu Zhang, Haitao Yang, Yonghua Du, Zhichuan J. Xu · 发表于：Chemistry of Materials · 年份：2017 · DOI：10.1021/acs.chemmater.7b04534 · 被引用次数：385 · 研究领域：Electrocatalysts for Energy Conversion、Electronic and Structural Properties of Oxides、Magnetic and transport properties of perovskites and related materials

LaCoO 3 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 IrO 2 and RuO 2 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 LaCoO 3 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 LaCoO 3 . Both DFT calculations and Superconducting Quantum Design (SQUID) magnetometer (MPMS-XL) showed a Co 3+ 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 LaCo 0.9 Fe 0.1 O 3 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 metal–oxygen covalency in oxide catalysts for OER.