Theoretical study of transition metal atom pairs anchored in g-CN monolayers for ammonia decomposition

Abstract

One way to efficiently store, transport, and utilize hydrogen is to convert it into liquid ammonia (NH3). Exploring low-cost and high-efficiency electrocatalysts for liquid ammonia oxidation reaction (AOR) is critical in developing hydrogen production fuel cells. Here, we have investigated the catalytic electro-oxidation of liquid ammonia on surfaces of transition metal dimer anchored in g-CN (TM2@g-CN) monolayer to derive insights into the reaction mechanism and evaluate the catalystic activity. Our results show that the mechanism proposed by Gerischer and Mauerer is kinetically preferred. Furthermore, Fe2, Co2, Ru2, Rh2, and Ir2 anchored in g-CN monolayer exhibit high AOR catalytic activity. In particular, Rh and Ir atoms exhibit excellent performance for hydrogen evolution reaction (HER), indicating that they can be used as the efficient bifunctional catalysts towards ammonia splitting for production H2. Remarkably, by regulating TM atoms with different d-electron numbers, the d-band center (εd) of TM atoms on TM2@g-CN can be turned and utilized to predict AOR performance, which provides a theoretical guideline for the design of advanced AOR electrocatalysts.