Electrochemical synthesis of ammonia from nitric oxide in a membrane electrode assembly electrolyzer over a dual Fe-Ni single atom catalyst

Abstract

Membrane electrode assembly (MEA) electrolyzers offer a means to scale up nitric oxide (NO)-to-ammonia (NH3) electro-conversion assisted by renewable electricity and bring the anthropogenic nitrogen cycle back into balance. Herein, we show that atomically dispersed dual Fe, Ni atom embedded nitrogen-doped carbon nanotube (FeNi-NCNT) electrodes produce NH3 readily with a low overpotential of 210 mV, among the lowest overpotentials reported for the electrosynthesis of NH3 from NO. The FeNi-NCNT catalyst attains a high NH3 faradaic efficiency (FENH) of 92.6% at −0.5 VRHE. The high selectivity of FeNi-NCNT is believed to result from Ni sites lowering the activation energy and offering a stable intermediate during NH3 formation. While integrating FeNi-NCNT in the MEA electrolyzer, high FENH of up to 83.6% was achieved at a current density of of about 71 mA cm−2, presenting steady electrolysis over 50 h. This work guides employing dual-atom catalysts in MEA electrolyzer applications for efficient feedstock production. © 2023 The Royal Society of Chemistry.