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.