Active-Spin-State-Derived Descriptor for Hydrogen Evolution Reaction Catalysis

Spin states are pivotal in modulating the electrocatalytic activity of transition-metal ™-based compounds, yet quantitatively evaluating the activity-spin state correlation remains a formidable challenge. Here, we propose an ‘activity index n’ as a descriptor, to assess the activity of the spin states for the hydrogen evolution reaction (HER). n descriptor integrates three key electronic parameters: the proportion (P), broadening range ® and center cc of active spin state, which collectively account for the electronic structure modulation induced by both the intrinsic active site and its local coordination environment. Using 1T-phase ZrSe2-anchored TM atoms (TM=Sc to Ni) as prototypes, we reveal that the correlation between Gibbs free energy and the n value follows a linear relation, namely, the vGH reduces as the n decreases. Notably, ZrSe2-Mn exhibits the optimal n value (-0.56), corresponding the best HER activity with a vGH of 0.04 eV closer to the thermoneutral ideal value (0 eV) than even Pt (vGH = -0.09 eV). This relationship suggests that n is the effective descriptor of active spin state for HER of TM-based catalysts. Our study brings fundamental insights into the HER activity-spin state correlation, offering new strategies for HER catalyst design.