Efficient Electrocatalytic Nitrate-to-Ammonia Enabled by Reversible Lattice-Oxygen Control
Qian Wu, Dongsheng Shao, Chencheng Dai, Jiarui Wang, Xiaoning Li, Pengfei Song, Wen Xie, Shibo Xi, Longcheng Zhang, Xiu Lin, Songzhu Luo, Shirong Sun, Li An, Pinxian Xi, Zhichuan J. Xu
Abstract
Understanding the fundamentals governing reactivity and leveraging this knowledge to achieve optimal catalytic performance have long been a core objective in catalysis study. This challenge is particularly pressing for sustainable nitrogen cycle via nitrate reduction (NO 3 – RR) due to its inherent trade-off between high Faradaic efficiency (FE) and low overpotential. Here, we propose a novel strategy to enhance the NO 3 – RR performance by quantitatively regulating surface oxygen activity of transition metal oxides (TMOs) via tuning the metal–oxygen covalency. Using a series of A-site-substituted La 1– x Sr x CoO 3 perovskites, we conduct comprehensive experimental and modeling studies, revealing that NH 3 yield rate and Faradaic efficiency exhibit distinct “volcano” and “W-shaped” dependencies on surface oxygen activity. Notably, La 0.5 Sr 0.5 CoO 3, characterized by balanced metal–oxygen covalency, achieves exceptional activity and selectivity for NO 3 – RR. Mechanistic studies uncover a switchable active site that transitions from a lattice-oxygen vacancy to a nonstoichiometric Co on La 1– x Sr x CoO 3 during NO 3 – RR, accompanied by a dynamic and reversible lattice-oxygen refilling process. This mechanism circumvents the potential-limiting step (PLS) and blocks byproduct formation, driving superior catalytic performance. Our discoveries provide insights for designing advanced TMOs for not only NO 3 – RR but also other oxygen-sensitive reactions, while deepening the understanding of surface dynamics during electrocatalysis.