Layered double hydroxides with atomic-scale defects for superior electrocatalysis Qixian Xie 1,§ , Zhao Cai 1,2,§ , Pengsong Li 1 , Daojin Zhou 1 , Yongmin Bi 1 , Xuya Xiong 1 , Enyuan Hu 3 , Yaping Li 1 , Yun Kuang 1 (), and Xiaoming Sun 1,4 () 1 State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China 2 Department of Chemistry and Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, USA 3 Chemistry Division, Brookhaven National Laboratory Upton, New York 11973, USA 4 College of Energy, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China § Qixian Xie and Zhao Cai contributed equally to this work. Received: 28 September 2017 Revised: 18 November 2017 Accepted: 24 February 2018 © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018 KEYWORDS selective defect engineering, atomic vacancy, layered double hydroxide, electrocatalysis, oxygen evolution reaction ABSTRACT Atomic composition tuning and defect engineering are effective strategies to enhance the catalytic performance of multicomponent catalysts by improving the synergetic effect; however, it remains challenging to dramatically tune the active sites on multicomponent materials through simultaneous defect engineering at the atomic scale because of the similarities of the local environment. Herein, using the oxygen evolution reaction (OER) as a probe reaction, we deliberately introduced base-soluble Zn(II) or Al(III) sites into NiFe layered double hydroxides (LDHs), which are one of the best OER catalysts. Then, the Zn(II) or Al(III) sites were selectively etched to create atomic M(II)/M(III) defects, which dramatically enhanced the OER activity. At a current density of 20 mA·cm −2 , only 200 mV overpotential was required to generate M(II) defect-rich NiFe LDHs, which is the best NiFe-based OER catalyst reported to date. Density functional theory (DFT) calculations revealed that the creation of dangling Ni–Fe sites (i.e., unsaturated coordinated Ni–Fe sites) by defect engineering of a Ni–O–Fe site at the atomic scale efficiently lowers the Gibbs free energy of the oxygen evolution process. This defect engineering strategy provides new insights into catalysts at the atomic scale and should be beneficial for the design of a variety of catalysts. 1 Introduction Catalysts with a variety of compositions have been demonstrated to effectively trigger many energy-related catalytic/electrocatalytic reactions, such as fuel-cell reactions [1, 2], water-splitting [3–7], and CO 2 reduction [8, 9], because of synergetic effects [4, 10]. To achieve higher catalytic efficiency and selectivity using these multicomponent catalysts, numerous efforts, including manipulation of the component ratios, atomic dispersion, and structure, have been made to regulate their surface electronic structures [11–14] and enhance their intrinsic activity [15–17]. For example, the incorporation of high-valence Mn(VI) and Co(III) into NiFe-based catalysts Address correspondence to Yun Kuang, kuangyun@mail.buct.edu.cn; Xiaoming Sun, sunxm@mail.buct.edu.cn Nano Research https://doi.org/10.1007/s12274-018-2033-9