Self-Triggering a Locally Alkaline Microenvironment of Co<sub>4</sub>Fe<sub>6</sub> for Highly Efficient Neutral Ammonia Electrosynthesis
Yang Yang, Yuting Sun, Yuning Wang, Xiaoxue Zhang, Wenyu Zhang, Zhen‐Feng Huang, Lichang Yin, Ali Han, Gang Liu
Abstract
Electrochemical nitrate reduction reaction (eNO 3 – RR) to ammonia (NH 3 ) holds great promise for the green treatment of NO 3 – and ambient NH 3 synthesis. Although Fe-based electrocatalysts have emerged as promising alternatives, their excellent eNO 3 – RR-to-NH 3 activity is usually limited to harsh alkaline electrolytes or alloying noble metals with Fe in sustainable neutral electrolytes. Herein, we demonstrate an unusual self-triggering localized alkalinity of the Co 4 Fe 6 electrocatalyst for efficient eNO 3 – RR-to-NH 3 activity in neutral media, which breaks down the conventional pH-dependent kinetics restrictions and shows a 98.6% NH 3 Faradaic efficiency (FE) and 99.9% NH 3 selectivity at −0.69 V vs RHE. The synergetic Co–Fe dual sites were demonstrated to enable the optimal free energies of eNO 3 – RR-to-NH 3 species and balance water dissociation and protonation of adsorbed NO 2 – . Notably, the Co 4 Fe 6 electrocatalysts can attain a high current density of 100 mA cm –2 with a high NH 3 FE surpassing 96% and long-term stability for over 500 h eNO 3 – RR-to-NH 3 in a membrane electrode assembly (MEA) electrolyzer. This work provides insight into tailoring the self-reinforced local-alkalinity on the Fe-based alloy electrocatalysts for eNO 3 – RR-to-NH 3 and thus avoids alkaline electrolytes and noble metals for practical sustainable nitrate upcycling technology.