Enhanced N2 Activation on a Composite Co3Mo3N Nitride and La0.6Sr0.4Co0.2Fe0.8O3 Perovskite Cathode for High-Temperature Electrochemical Ammonia Synthesis

Abstract

Electrochemical routes for ammonia synthesis could offer improved conversion efficiency, compatible integration with renewable energy sources, and a solution to distributed chemical production. In a conventional Haber–Bosch process, ammonia, NH3, is produced by reacting N2 and H2 at high temperatures and pressures. In an electrochemical pathway, the H2 production and pressurization steps can be bypassed by using N2 and H2O in an ambient-pressure solid-oxide electrolysis cell (SOEC). In this study, a SOEC with a composite cathode of A-site deficient lanthanum ferrite perovskite oxide and transition metal nitride Co3Mo3N was fabricated, and its activity for the nitrogen reduction reaction (NRR) was studied. The composite cathode produced ammonia at a rate of 4.0 × 10–11 mol s–1 cm–2 at 550 °C and 0.65 mA/cm2, which was an 8-fold enhancement compared to either of the pure phase electrodes. Relevant properties of Co3Mo3N, such as thermochemical stability, adsorption behavior, and mobility of nitrogen ions, were characterized by various techniques including in situ XRD, XAFS/XANES, NAP-XPS, temperature-programmed experiments, and in situ DRIFTS.