Electrocatalytic CO ₂ Reduction Empowered by 2D Hexagonal Transition Metal Borides

Abstract Electrocatalysis holds immense promise for producing high‐value chemicals and fuels through the carbon dioxide reduction reaction (CO ₂ RR), advancing global sustainability and carbon neutrality. However, conventional electrocatalysts based on transition metals are often limited by significant overpotentials. Since the discovery of the first hexagonal MAB ( h ‐MAB) phase, Ti ₂ InB ₂ , and its 2D derivative in 2019, 2D hexagonal transition metal borides ( h ‐MBenes) have emerged as promising candidates for various electrochemical applications. This study presents the first theoretical investigation into the CO ₂ RR catalytic properties of pristine h ‐MBenes ( h ‐MB) and their ─O ( h ‐MBO) and ─OH ( h ‐MBOH) terminated counterparts, focusing on metals such as Sc, Ti, V, Zr, Nb, Hf, and Ta. These results reveal while h ‐MB and h ‐MBO exhibit poor catalytic performance due to overly strong or weak interactions with CO ₂ , h ‐MBOH shows great promise. Notably, ScBOH, TiBOH, and ZrBOH display exceptionally low limiting potentials ( U _L ) of −0.46, −0.53, and −0.64 V, respectively. These findings uncover the unique role of ─OH in tuning the electronic properties of h ‐MBenes, thereby optimizing intermediate adsorption, which prevents excessive binding and enhances catalytic efficiency. This research offers valuable insights into the potential of h ‐MBenes as highly efficient CO ₂ RR catalysts, underscoring their versatility and significant prospects for electrochemical applications.