h-MBenes (M/B = 1:1) as Promising Electrocatalysts for Nitrogen Reduction Reaction: A Theoretical Study

MAB phases and their two-dimensional (2D) derivatives MBenes have attracted increasing attention in electrochemical catalysis because of their unique structures and inherent electronic properties. Since the first hexagonal MAB (h-MAB) phase Ti₂InB₂ and 2D TiB h-MBene were discovered in 2019, the family of h-MBenes shows a promising perspective in electrochemical applications. In this work, the electrochemical nitrogen reduction reaction (eNRR) properties of discovered h-MBenes are studied theoretically for the first time. A volcano-shaped relationship between the limiting potential (U_L) and the adsorption energy of the **NNH group (ΔE_NNH) is established. Moreover, it is found that the catalytic activity can be engineered by the bimetallic alloying effect, which applies to both in-plane ordered h-M′_2/3M″_1/3B phases and h-MBs with a second transition metal alloyed. Remarkably, guided by the revealed volcano-shaped relationship, Rh-alloyed hexagonal 2D WB and NbB with U_L as small as −0.34 and −0.56 V, respectively, are designed. Finally, the transition metal alloying is revealed to regulate the orbital energy redistribution, consequently adjusting the binding strength of N-containing intermediates with h-MBene surfaces to an appropriate range. This work unravels the promise of h-MBenes as eNRR catalysts and can shed light on the potential for h-MBenes in extensive electrochemical applications.