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 (FE_NH3) of 92.6% at −0.5 V_RHE. 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 FE_NH3 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.