Efficient screening rooted in a series of transition-metal atom anchored conjugated organic frameworks toward multifunctional HER/OER/ORR via modification of chalcogen ligands: a machine learning and constant potential study

Abstract

The pursuit of two-dimensional single-atom catalysts (SACs) holds far-reaching significance for advancing energy conversion and storage technologies by providing efficient, stable, and low-cost alternatives to precious metals for hydrogen evolution (HER), oxygen evolution (OER), and oxygen reduction reactions (ORR). The synergy between the tunable ligands, abundant transition metal active sites, and diverse substrate materials opens new avenues for realizing both stability and enhanced catalytic activity. This study presents a thorough examination of the catalytic HER/OER/ORR activities in 161 TM@C₁₅N₆XY₂H₅ SACs, combing density functional theory with machine learning. Thirteen configurations were identified, comprising 11 single-function OER/ORR catalysts, a bifunctional OER/ORR catalyst Cu@C₁₅N₆O₃H₅, and notably, Au@C₁₅N₆OS₂H₅ , which demonstrates trifunctional HER/OER/ORR catalytic activity. A pronounced hybridization between Cu/Au-d orbitals and O-p orbitals of oxygenated adsorbates directs lone electrons to antibonding states before transitioning to bonding orbitals, enabling efficient adsorption of oxygenated intermediates on the surface. The data obtained through ML applications indicate that the atomic radius ( r_TM) and electronegativity ( χ) of TM are the primary descriptors for HER activity, while the d-electron count (θ) and atomic radius (r_TM) of the atoms are the key descriptors for OER/ORR activities. Utilizing SISSO method, a clear and robust correlation between intrinsic properties and adsorption energy was derived, realizing each-step prediction. Additionally, the constant-potential model shows that electric double-layer capacitance modulates the reaction barrier, meanwhile, pH- and voltage-dependent adsorption free energies indicate that acidic and alkaline conditions (pH 5.3/9.9, Cu@C₁₅N₆O₃H₅/Au@C₁₅N₆OS₂H₅ ) enhance OER efficiency, while pH 0 is optimal for ORR.