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

TL;DR

This paper introduces a new electronic descriptor called 'activity index n' that effectively correlates the spin state of transition-metal catalysts with their hydrogen evolution reaction activity, guiding better catalyst design.

Contribution

The study proposes the 'activity index n' as a quantitative descriptor linking spin states to HER activity, validated on ZrSe2-anchored transition metals, and demonstrates its predictive power for catalyst performance.

Findings

n correlates linearly with Gibbs free energy changes in HER.

ZrSe2-Mn exhibits the optimal n value and superior HER activity.

n outperforms traditional descriptors in predicting HER activity.

Abstract

Spin states are pivotal in modulating the electrocatalytic activity of transition-metal (TM)-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 (R) 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.