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
Abstract
High Resolution Image Download MS PowerPoint Slide The electrocatalytic nitrate (NO 3 – ) 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 0.9 M 0.1 O 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 0.9 Cu 0.1 O 3−δ (LF 0.9 Cu 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 0.9 Cu 0.1 submicrofibers can induce NO 3 – 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 (*NO 3 + H + + e – → *HNO 3 ) 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.