Deciphering Indirect Nitrite Reduction to Ammonia in High‐Entropy Electrocatalysts Using In Situ Raman and X‐ray Absorption Spectroscopies

Abstract

This research adopts a new method combining calcination and pulsed laser irradiation in liquids to induce a controlled phase transformation of Fe, Co, Ni, Cu, and Mn transition‐metal‐based high‐entropy Prussian blue analogs into single‐phase spinel high‐entropy oxide and face‐centered cubic high‐entropy alloy (HEA). The synthesized HEA, characterized by its highly conductive nature and reactive surface, demonstrates exceptional performance in capturing low‐level nitrite (NO2−) in an electrolyte, which leads to its efficient conversion into ammonium (NH4+) with a Faradaic efficiency of 79.77% and N selectivity of 61.49% at −0.8 V versus Ag/AgCl. In addition, the HEA exhibits remarkable durability in the continuous nitrite reduction reaction (NO2−RR), converting 79.35% of the initial NO2− into NH4+ with an impressive yield of 1101.48 µm h−1 cm−2. By employing advanced X‐ray absorption and in situ electrochemical Raman techniques, this study provides insights into the indirect NO2−RR, highlighting the versatility and efficacy of HEA in sustainable electrochemical applications.