Zhu, YinlongTahini, HassanHu, ZhiweiChen, Zhi-gangZhou, WeiKomarek, Alexander C.Lin, QianLin, Hong-JiChen, Chien-TeZhong, YijunFernandez-Diaz, M. T.Smith, SeanWang, HuantingLiu, MeilinShao, Zongping2020-06-160935-9648http://hdl.handle.net/1885/205180Developing efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) is of paramount importance to many chemical and energy transformation technologies. The diversity and flexibility of metal oxides offer numerous degrees of freedom for enhancing catalytic activity by tailoring their physicochemical properties, but the active site of current metal oxides for OER is still limited to either metal ions or lattice oxygen. Here, a new complex oxide with unique hexagonal structure consisting of one honeycomb-like network, Ba4Sr4(Co0.8Fe0.2)4O15 (hex-BSCF), is reported, demonstrating ultrahigh OER activity because both the tetrahedral Co ions and the octahedral oxygen ions on the surface are active, as confirmed by combined X-ray absorption spectroscopy analysis and theoretical calculations. The bulk hex-BSCF material synthesized by the facile and scalable sol-gel method achieves 10 mA cm−2 at a low overpotential of only 340 mV (and small Tafel slope of 47 mV dec−1) in 0.1 m KOH, surpassing most metal oxides ever reported for OER, while maintaining excellent durability. This study opens up a new avenue to dramatically enhancing catalytic activity of metal oxides for other applications through rational design of structures with multiple active sites.This work was financially supported by the Defense industrial technology development program (Grant No. JCKY2018605B006), National Nature Science Foundation of China (Grant No. 21576135), the Jiangsu Nature Science Foundation for Distinguished Young Scholars (Grant No. BK20170043), and the Australian Research Council (Discovery Early Career Researcher Award No. DE190100005).8 pagesapplication/pdfen-AU© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. https://authorservices.wiley.com/author-resources/Journal-Authors/licensing/self-archiving.html This is the peer reviewed version of the following article Yinlong Zhu et al, Boosting Oxygen Evolution Reaction by Creating Both Metal Ion and Lattice‐Oxygen Active Sites in a Complex Oxide, Advanced Materials 32 (1) 12 November 2019, doi 10.1002/adma.201905025, which has been published in final form at https://doi.org/10.1002/adma.201905025. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions (Publisher journal website 22/6/2020)complex oxides, coordination environment, dual active sites, honeycomblike structures, oxygen evolution reaction2019-11-1210.1002/adma.2019050252020-01-12