2D anti-MXene boride monolayers: unveiling a promising new family of catalysts for the nitrogen reduction reaction

Abstract

This study presents a comprehensive computational analysis focusing on the electrochemical nitrogen reduction reaction (NRR) catalytic activity of two-dimensional anti-MXene borides. Employing density functional theory (DFT), we systematically assessed the dynamic, mechanical, and thermal stabilities of 23 anti-MXene boride structures, ultimately selecting five: CoB, FeB, IrB, MnB, and OsB for an in-depth investigation of their catalytic efficiency. Additionally, our study included both pristine and boron-deficient variants to elucidate their performance in catalytic processes. Our findings pinpoint FeB and OsB as prime catalysts with notably low limiting potentials of 0.30 eV and 0.48 eV, respectively, when considering solvation effects, compared to 0.32 eV and 0.64 eV without solvation effects. We also observed a reduction in kinetic barriers for the potential-determining step (PDS) with activation energies of 0.15 eV and 0.30 eV on FeB and OsB, respectively. Applied voltage calculations revealed that these materials remain efficient catalysts under operational conditions, with overpotentials of 0.41 eV for FeB and 0.73 eV for OsB. The investigation explored their electronic structures, revealing the distinctive planarity of MnB along with the buckled nature of the others, characterized by active boron sites. Additionally, the impact of boron vacancies on catalysis was examined, highlighting a trade-off between enhanced N₂ adsorption and increased energy barriers. A pivotal discovery was the establishment of a linear correlation between the φ descriptor derived from the d-electron count and electronegativity of the transition metals and the limiting potential, offering predictive insights into electrocatalytic performance. This study advances the development of efficient and sustainable anti-MXene boride electrocatalysts.