Efficient Nitrate to Ammonia Conversion on Bifunctional IrCu₄ Alloy Nanoparticles.

Abstract

Electrochemical nitrate reduction (NO₃RR) to ammonia presents a promising alternative strategy to the traditional Haber-Bosch process. However, the competitive hydrogen evolution reaction (HER) reduces the Faradaic efficiency toward ammonia, while the oxygen evolution reaction (OER) increases the energy consumption. This study designs IrCu₄ alloy nanoparticles as a bifunctional catalyst to achieve efficient NO₃RR and OER while suppressing the unwanted HER. This is achieved by operating the NO₃RR at positive potentials using the IrCu₄ catalyst, which allows a Faradaic efficiency of 93.6% for NO₃RR. When applied to OER catalysis, the IrCu₄ alloy also shows excellent results, with a relatively low overpotential of 260 mV at 10 mA cm^-2. Stable ammonia production can be achieved for 50 h in a 16 cm² flow electrolyzer in simulated working conditions. Our research provides a pathway for optimizing NO₃RR through bifunctional catalysts in a tandem approach.