Title: Tailoring the Electronic Structures of the La2NiMnO6 Double Perovskite as Efficient Bifunctional Oxygen Electrocatalysis

Authors: Mei Qu, Xingyu Ding, Zechao Shen, Meiyan Cui, Freddy E. Oropeza, Giulio Gorni, Victor A. de la Peña O’Shea, Wei Li, Dong-Chen Qi*, and Kelvin H. L. Zhang*

Abstract: Double perovskite oxides are one of the most promising bifunctional electrocatalysts for efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) due to their adjustable electronic structures via doping with different metal cations or engineering of defects. Herein, we report a systematic study on the tuning of the electronic structure of La_2–xSr_xNiMnO₆ with 0 ≤ x ≤ 1.0 to promote the bifunctional OER/ORR activity. The bifunctional index (ΔE) is substantially reduced with increasing of Sr contents and achieves an optimal value of 0.85 V for La_1.4Sr_0.6NiMnO₆, exceeding that of widely studied LaNiO₃. Our study on electronic structures reveals that the enhancement of the ORR and OER activities strongly correlates with the appearance of Ni³⁺ oxidation states and the upshift of the O 2p-band center promoted by Sr doping. Furthermore, an increase of hole states, derived from Ni³⁺ states, reduces the energy barrier for the electron transfer from 0.44 to 0.12 eV and hence improves the intrinsic OER activities. The tuning of the electronic structure that leads to higher OER and ORR activities in La_2–xSr_xNiMnO₆ can be extended to other materials for the design of active bifunctional electrocatalysts.

Full-Link: https://pubs.acs.org/doi/10.1021/acs.chemmater.0c04527