Understanding the Mechanistic Pathways of N2 Reduction to Ammonia on (110) Facets of Transition Metal Carbides

Abstract

The conversion of molecular dinitrogen into ammonia under mild conditions is a significant pursuit in chemistry due to its potential for sustainable and clean ammonia production. The electrochemical reduction of N2 offers a promising route for achieving this goal with reduced energy consumption, utilizing renewable energy sources. However, the exploration of effective electrocatalysts for this process, particularly at room temperature and atmospheric pressure, remains under exploration. This study addresses this gap by conducting a comprehensive investigation of potential catalysts for nitrogen electro-reduction to ammonia under ambient conditions. Using density functional theory calculations, we explore the (110) facets of rock salt structures across 11 transition metal carbides. Catalytic activity is evaluated through the construction of free energy diagrams for associative, dissociative, and Mars–van Krevelen reaction mechanisms. Additionally, we assess material stability against electrochemical poisoning and decomposition of parent metals during operation. Our findings suggest that a few of the candidates are promising for nitrogen reduction reactions, such as TaC and WC, with moderate onset potentials (−0.66 V and −0.82 V vs. RHE) under ambient conditions.