Cation Substitution Strategy for Developing Perovskite Oxide with Rich Oxygen Vacancy-Mediated Charge Redistribution Enables Highly Efficient Nitrate Electroreduction to Ammonia

Kaibin Chu; Wei Zong; Guohao Xue; Hele Guo; Jingjing Qin; Haiyan Zhu; Nan Zhang; Zhihong Tian; Hongliang Dong; Yue-E Miao; Maarten B J Roeffaers; Johan Hofkens; Feili Lai; Tianxi Liu

doi:10.1021/jacs.3c06402

Cation Substitution Strategy for Developing Perovskite Oxide with Rich Oxygen Vacancy-Mediated Charge Redistribution Enables Highly Efficient Nitrate Electroreduction to Ammonia

J Am Chem Soc. 2023 Oct 4;145(39):21387-21396. doi: 10.1021/jacs.3c06402. Epub 2023 Sep 20.

Authors

Kaibin Chu^{1

2}, Wei Zong¹, Guohao Xue¹, Hele Guo², Jingjing Qin¹, Haiyan Zhu¹, Nan Zhang¹, Zhihong Tian³, Hongliang Dong⁴, Yue-E Miao⁵, Maarten B J Roeffaers⁶, Johan Hofkens^{2

7}, Feili Lai^{2

7

8}, Tianxi Liu¹

Affiliations

¹ The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, International Joint Research Laboratory for Nano Energy Composites, Jiangnan University, Wuxi 214122, China.
² Department of Chemistry, KU Leuven, Celestijnenlaan 200F, Leuven 3001, Belgium.
³ Engineering Research Center for Nanomaterials, Henan University, Kaifeng 475004, China.
⁴ Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China.
⁵ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.
⁶ cMACS, Department of Microbial and Molecular Systems, KU Leuven, Celestijnenlaan 200F, Leuven 3001, Belgium.
⁷ Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany.
⁸ John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.

Abstract

The electrocatalytic nitrate (NO₃^-) reduction reaction (eNITRR) is a promising method for ammonia synthesis. However, its efficacy is currently limited due to poor selectivity, largely caused by the inherent complexity of the multiple-electron processes involved. To address these issues, oxygen-vacancy-rich LaFe_0.9M_0.1O_3-δ (M = Co, Ni, and Cu) perovskite submicrofibers have been designed from the starting material LaFeO_3-δ (LF) by a B-site substitution strategy and used as the eNITRR electrocatalyst. Consequently, the LaFe_0.9Cu_0.1O_3-δ (LF_0.9Cu_0.1) submicrofibers with a stronger Fe-O hybridization, more oxygen vacancies, and more positive surface potential exhibit a higher ammonia yield rate of 349 ± 15 μg h^-1 mg^-1_cat. and a Faradaic efficiency of 48 ± 2% than LF submicrofibers. The COMSOL Multiphysics simulations demonstrate that the more positive surface of LF_0.9Cu_0.1 submicrofibers can induce NO₃^- enrichment and suppress the competing hydrogen evolution reaction. By combining a variety of in situ characterizations and density functional theory calculations, the eNITRR mechanism is revealed, where the first proton-electron coupling step (*NO₃ + H⁺ + e^- → *HNO₃) is the rate-determining step with a reduced energy barrier of 1.83 eV. This work highlights the positive effect of cation substitution in promoting eNITRR properties of perovskites and provides new insights into the studies of perovskite-type electrocatalytic ammonia synthesis catalysts.