A Newly Predicted Magnetic TMB6 Monolayer for Efficient Nitrogen Fixation

Developing electrocatalysts for the N₂ reduction reaction (NRR) with high activity, high selectivity, and low cost is urgently required to enhance the NH₃ yield rate. Based on first-principles calculations, we predict a series of new transition metal boride TMB₆ (TM = Ti, V, Cr, Mn, Fe, and Co) monolayers and investigate their magnetoelectronic and electrocatalytic properties. The results reveal that VB₆ and CoB₆ favor ferromagnetic coupling, while TiB₆, CrB₆, MnB₆, and FeB₆ display antiferromagnetic ordering. Furthermore, TiB₆ exhibits a high Néel temperature of 344 K and a large magnetic anisotropy energy of 614 μeV per Ti atom. Most interestingly, TiB₆ and VB₆ exhibit superior NRR catalytic activity with a limiting potential of -0.50 and -0.19 V, respectively, and favorable NRR selectivity over the HER. Finally, the structural stability of TMB₆ monolayers has been confirmed by a set of phonon dispersion, molecular dynamics, and elastic constant calculations. Our results highlight the use of the newly designed two-dimensional (2D) TM borides as promising candidates for spintronic devices and nitrogen fixation applications.