Mixed Fe-Mo carbide prepared by a sonochemical synthesis as highly efficient nitrate reduction electrocatalyst

TL;DR

This study presents a sonochemically synthesized mixed Fe-Mo carbide catalyst that efficiently reduces nitrates to ammonia, with high yield and selectivity, and demonstrates its application in a Zn-NO3 battery for simultaneous ammonia generation.

Contribution

It introduces a novel synthesis method for mixed Fe-Mo carbides and demonstrates their high electrocatalytic activity for nitrate reduction and ammonia production.

Findings

Achieved NH3 yield of 14.66 mg h-1 cm-2 at -0.3 V vs RHE

FE of 94.35% for nitrate reduction to NH3

Demonstrated ammonia generation in a Zn-NO3 battery with 88% FE

Abstract

Ammonia, a versatile compound that can be used as a fertilizer, chemical or fuel, has since long been produced through the energy-intensive Haber-Bosch process. Recently, the electrochemical nitrate reduction reaction (NO3RR) using electricity generated from renewable sources has attracted widespread attention. However, the complex reaction pathway of NO3RR leads to the formation of many undesirable by-products. Herein we successfully prepared a mixed (FeMo)2C catalyst with good electrocatalytic NO3RR, having a NH3 yield of 14.66 mg h-1 cm-2 and an FE of 94.35 % at low potential -0.3 V vs RHE. DFT calculations show that the presence of Fe in Mo2C lattice changes the reaction mechanism, decreasing the potential barrier to be overcome from 1.36 to 0.89 eV. In addition, mixed Fe-Mo carbide facilitates the adsorption of intermediates and promotes NH3 desorption, facilitating NO3- reduction to NH3. In addition, (FeMo)2C was used as cathode for Zn-NO3 battery to generate electricity, producing ammonia at the same time, with a power density of 3.8 mWcm-2 and an NH3 FE of 88 %. This work describes a new synthesis method for mixed metal carbides and provides a promising strategy for NH3 production.