Oxygen Vacancy‐Rich La 0.5 Sr 1.5 Ni 0.9 Cu 0.1 O 4–δ as a High‐Performance Bifunctional Catalyst for Symmetric Ammonia Electrolyzer

Abstract In this study, strontium and copper dual‐doped La 2 NiO 4 annealed in Ar (La 0.5 Sr 1.5 Ni 0.9 Cu 0.1 O 4‐δ ‐Ar, LSNC‐Ar) with K 2 NiF 4 structure is strategically designed as an ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) bifunctional catalyst for high‐efficiency ammonia electrolysis. The selective substitution of lanthanum with high content strontium improves the electronic conductivity and increases the oxygen vacancy concentration. Doping of Cu into the B‐site of the perovskite induces a synergistic interplay of Ni and Cu, leading to excellent AOR activity. Due to the excellent AOR and HER activity of doped La 2 NiO 4 , a symmetric ammonia electrolyzer based on LSNC‐Ar (SAE‐LSNC‐Ar) is assembled and investigated for the removal of ammonia. In addition, the performance of the SAE is comparable to the ammonia electrolyzer based on a PtIr/C anode and Pt/C cathode at low voltage. This is the first report using an oxide with the K 2 NiF 4 structure as an efficient AOR catalyst. The assembled SAE‐LSNC‐Ar shows ≈95% ammonia removal efficiency in real landfill leachate, which is the highest among electrochemical removal of ammonia in landfill leachate. This study paves an attractive route to explore materials with the K 2 NiF 4 structure as highly efficient AOR/HER bifunctional catalysts for the electrolysis of ammonia.