Pulsed Laser‐Twisted Spinel‐to‐Rocksalt High‐Entropy 3 d ‐Metal Oxides for Selective Ammonia Electrosynthesis

Abstract The electrochemical synthesis of ammonia (NH ₃ ) via the nitrate reduction reaction (eNO ₃ RR) intends an efficient replacement to the Haber–Bosch technique, operating under ambient conditions. Nitrate‐based voltaic cells present a multifunctional system by simultaneously removing wastewater pollutants, producing NH ₃ , and generating energy. Herein, high‐entropy spinel oxide (HE‐SPO) derived from divalent (Mn, Fe, Co, Ni, and Cu) 3 d transition metals are transformed into single‐phase (MnFeCoNiCu)O high‐entropy rock‐salt oxides (HE‐RSO) via pulsed laser irradiation in liquids, achieving high‐entropy phase twisting with structural stabilization. The HE‐RSO electrocatalyst demonstrated exceptional eNO ₃ RR‐to‐NH ₃ conversion, with an NH ₃ production rate of 15.34 mg h ⁻¹ cm ⁻² at −0.4 V versus RHE and a Faradaic efficiency of 92%. In situ Raman spectroscopy revealed Co and Cu as dual‐active sites, facilitating the N‐end mechanism for eNO ₃ RR, which is further validated via density functional theory calculations. Leveraging this high‐efficiency eNO ₃ RR‐to‐NH ₃ system, the HE‐RSO catalyst is integrated into a Zn–nitrate battery, reaching a high output voltage of 1.22 V and a power density of 1.75 mW cm ⁻² . This study highlights the pulsed laser process as a new avenue for high‐entropy structural stabilization and underscores the potential of HE‐RSO for sustainable NH ₃ production and integrated energy applications.