Electrochemical Ammonia Generation Directly from Nitrogen and Air Using an Iron-Oxide/Titania-Based Catalyst at Ambient Conditions.

Abstract

Ammonia was produced electrochemically from nitrogen/air in aqueous alkaline electrolytes by using a Fe2O3/TiO2 composite catalyst under room temperature and atmospheric pressure. At an applied potential of 0.023 V versus reversible hydrogen electrode, the rate of ammonia formation was 1.25 × 10-8 mmol mg-1 s-1 at an overpotential of just 34 mV. This rate increased to 2.7 × 10-7 mmol mg-1 s-1 at -0.577 V. The chronoamperometric experiments on Fe2O3/TiO2/C clearly confirmed that Fe2O3 along with TiO2 shows superior nitrogen reduction reaction activity compared to Fe2O3 alone. Experimental parameters such as temperature and applied potential have a significant influence on the rate of ammonia formation. The activation energy of nitrogen reduction on the employed catalyst was found to be 25.8 kJ mol-1. Real-time direct electrochemical mass spectrometry analysis was used to monitor the composition of the evolved gases at different electrode potentials.