Computational design and descriptor development for metal single atoms anchored on CrP2 monolayer toward efficient electrocatalytic water splitting

The rational design of efficient electrocatalysts is essential for addressing the global crisis, but developing bifunctional catalysts that simultaneously promote both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) remains a significant challenge. In this study, we conducted a comprehensive first-principles investigation of transition metal single atoms anchored on a two-dimensional CrP₂ monolayer as potential electrocatalysts for overall water splitting. Among the evaluated systems, Fe@CrP₂ achieves nearly optimal hydrogen adsorption with a ΔG_H∗ of 0.01 eV, while Co@CrP₂ exhibits outstanding bifunctional performance, achieving low overpotentials of 0.08 V for HER and 0.39 V for OER. To elucidate the origin of the catalytic activity, we developed two physically interpretable descriptors (χ for HER and υ for OER), derived from a combination of fundamental structural and electronic features including the d band center, Fermi level, ionization energy, valence electron count, atomic radius, TM-P bond length, and work function. These descriptors establish strong linear correlations with the calculated adsorption energies and demonstrate excellent transferability to analogous MoP₂-based systems while retaining predictive accuracy. This work reveals essential structure–activity relationships in single-atom catalysts formed by transition metal atoms anchored on two-dimensional phosphide monolayers, and provides a generalizable framework for the rational design of high-performance electrocatalysts for water splitting.