In situ exsolved CoFe alloys over perovskite toward enhanced ammonia synthesis

Abstract

Ammonia (NH₃) is an easy to store, zero-carbon emission hydrogen carrier. The current primary challenges in enhancing the yield and faradaic efficiency of the electrocatalytic nitrogen reduction reaction (NRR) for ammonia synthesis are widely recognized to be the inhibition of the competing hydrogen evolution reaction (HER) and the activation of NN to facilitate its cleavage. Here we select perovskite oxide materials La_0.6Sr_0.4Co_0.2Fe_0.8+xO_3−δ (LSCF_0.8+x, x = 0–0.1) as the NRR electrode for the proton-conducting solid oxide electrolyzer cells (PCECs). We construct a more effective metal oxide interface via in situ exsolution of CoFe alloy nanoparticles (NPs), which promotes NN activation and cleavage by applying a certain voltage at 500 °C, thereby accelerating the gradual synthesis of NH₃ with proton H⁺. At 500 °C and 0.8 V, the maximum NH₃ synthesis rate is 3.75 × 10⁻⁹ mol s⁻¹ cm⁻² while the highest faradaic efficiency is 3.05%, and there is no damage to the microstructure after continuously working for 100 h, indicating that this material as the electrode is beneficial to the electrocatalytic synthesis of ammonia in PCECs.