Enhanced Electrocatalytic Conversion of Nitrates to Ammonia: Fuel from Waste

Abstract

Ammonia (NH3) is globally one of the most produced chemicals. Despite being known for its use as a fuel and as a precursor of multiple chemicals, during its production, it is responsible for more than 1.2 % of the total global CO2 emission and consumes a large amount of energy. In this work, we studied a flow-through membrane-free electrocatalytic device (CMED) to produce continuous stream of NH3 from a common water contaminant, nitrate (NO3−). Indium-palladium (In−Pd) nanoparticles were impregnated in activated carbon cloth (ACC) and used as a cathode in the electrochemical device. It is found that in the counter electrode, adding oxygen evolution reaction (OER) active catalysts like platinum (Pt) for the regeneration of hydrogen ions enhances the rate of ammonia conversion to 7.28 μmol min−1 cm−2, eliminate the production of toxic nitrite by-products, as well as provide a platform for a stable energy consumption over long periods of time. This method for the conversion of NO3− into NH3 promises a way forward for sustainable resource utilization while generating fuel from waste and contributing to future circular economies, and managing the nitrogen cycle in water that is a major challenge of the 21st century society.