Single atom catalysis perspective to reveal N2 and NRR intermediate adsorption properties on non-benzenoid carbon allotrope: A DFT study

Abstract

In this work, the adsorption behavior of N₂ and the Nitrogen Reduction Reaction (NRR) intermediates have been explored on TM (3d group from Sc to Ni) embedded non-benzenoid Carbon Allotrope (BPN) employing density functional theory calculations. Following the exploration of the stability of the transition metal atoms embedded on two different defective sites on BPN, the fundamental electronic properties, such as atomic charges, and other chemical bonding properties, such as (COHP and COBI) have been elucidated. Then, the molecular adsorption behaviors were investigated to determine the best material and possible NRR pathway. Our findings show that the N₂ molecule is adsorbed in end-on geometry, which implies that the distal/alternate (or their mixture) pathway might be mostly followed to synthesize NH₃, also supported by the bond length variations of reaction intermediates, which support N-N bond scission during the reaction. A discussion was made to predict NNH* adsorption energy through chemical bonding descriptors belonging to the bare TM embedded layers. The most striking aspect of this work, ICOBI is a very effective descriptor for predicting the adsorption energy of the NNH* intermediate, which is crucial for the NRR process. Finally, Fe-BPN layer is predicted to have a best selectivity in favor of NRR, while Sc-BPN layer promotes HER.