Synergistic role of p−d hybridization and magnetism in enhanced water splitting on ferromagnetic 1T transition metal dichalcogenides

Orbital hybridization within the $d$-band model has been widely recognized as an important factor affecting the catalytic properties of materials. Separately, the spin degrees of freedom have also been gaining increasing attention in catalytic processes on magnetic substrates. Here, using first-principles calculations based on density functional theory, we systematically investigate the catalytic activity of ferromagnetic $M{X}_{2}$ ($M$ = V, Cr, Mn; $X$ = Se, Te) in the $1T$ phase, focusing on water splitting. Our studies show that $\mathrm{1T}\text{\ensuremath{-}}{\mathrm{VSe}}_{2}$ and $\mathrm{1T}\text{\ensuremath{-}}{\mathrm{VTe}}_{2}$ are excellent catalysts for the crucial constituent steps of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. The enhanced reactivities in these two systems over the other four counterparts can be traced to the synergistic effects of magnetism and strong hybridization between the $p$ orbitals of $X$ and $d$ orbitals of V. We also propose a modified descriptor of ${\mathrm{\ensuremath{\Delta}}}_{\ensuremath{\sigma}{\ensuremath{\sigma}}^{*}}$ to characterize the HER activity, defined by the bonding and antibonding energy splitting, and further demonstrate that the magnetic properties of the catalysts should be explicitly accounted for in both reactions. The present findings may shed light on a microscopic understanding of the physical mechanisms of various catalytic reactions on two-dimensional magnets.