Computational Discovery of Tetragonal MBene Phase: Diamond-Shaped Boron Lattices, Viable MAB Precursors, and Selective CO 2 Reduction

Abstract

MBenes are a class of two-dimensional transition-metal borides derived from layered MAB phases. Here we use first-principles calculations to predict a new tetragonal MB (1:1) MBene phase featuring a diamond-shaped B-B lattice and systematically assess its phase stability, synthetic accessibility, and catalytic performance towards CO 2 reduction reaction (CO 2 RR). Four tetragonal configurations are benchmarked against known hexagonal and orthorhombic phases, and a multi-tier screening identifies six robust members (CrB, FeB, MoB, WB, IrB, and PtB).Exploration of the I4/mmm MAB space reveals 13 viable precursors, including the experimentally synthesized Ir 2 ZnB 2 , which validates our screening approach. CO 2 RR free-energy diagrams show that CrB favors CH 3 OH while FeB, MoB, WB, IrB, and PtB preferentially yield HCOOH. The corresponding limiting potentials are competitive with, and in some cases superior to, those reported for state-of-the-art orthorhombic and hexagonal MBenes. These findings expand the MBene landscape by establishing a tetragonal phase with structural, synthetic, and catalytic promise.