Are (100) facets of transition metal carbonitrides suitable as electrocatalysts for nitrogen reduction to ammonia at ambient conditions?

Abstract

Sustainable and energy-efficient ammonia production requires facile nitrogen reduction for hydrogen preservation and inorganic fertilizers. A nitrogen reduction apparatus with optimal stability, selectivity, and activity for ambient temperatures and pressure is needed to catalyze ammonia synthesis. This paper describes the investigation of using transition metal carbonitrides as catalyst to reduce molecular nitrogen electrochemically to NH3 at room temperature and atmospheric pressure. Density functional theory calculations determine the competition among associative, dissociative, and Mars-van Krevelen mechanisms where in most cases the Mars-van Krevelen is a more favorable reaction pathway. VCN and NbCN are the best candidates for ammonia production via the Mars-van Krevelen mechanism at low onset potentials of −0.52 V and −0.53 V vs reversible hydrogen electrode on the (100) facets. These carbonitrides are predicted to favor nitrogen reduction reaction rather than hydrogen evolution reaction.