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 Neel temperature of 344 K and a large magnetic anisotropy energy of 614 mu eV 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.