Designing an alkali-metal-like superatom Ca3B for ambient nitrogen reduction to ammonia

Abstract

Converting earth-abundant nitrogen (N₂) gas into ammonia (NH₃) under mild conditions is one of the most important issues and a long-standing challenge in chemistry. Herein, a new superatom Ca₃B was theoretically designed and characterized to reveal its catalytic performance in converting N₂ into NH₃ by means of density functional theory (DFT) computations. The alkali-metal-like identity of this cluster is verified by its lower vertical ionization energy (VIE, 4.29 eV) than that of potassium (4.34 eV), while its high stability was guaranteed by the large HOMO–LUMO gap and binding energy per atom (E_b). More importantly, this well-designed superatom possesses unique geometric and electronic features, which can fully activate N₂via a “double-electron transfer” mechanism, and then convert the activated N₂ into NH₃ through a distal reaction pathway with a small energy barrier of 0.71 eV. It is optimistically hoped that this work could intrigue more endeavors to design specific superatoms as excellent catalysts for the chemical adsorption and reduction of N₂ to NH₃.