Design of Multifunctional Catalysts and Potential-Dependent Inverted Adsorption: A Sweet Marriage of Synergistic “Genome” Investigated by Machine Learning and First-Principles Calculations

The pursuit of two-dimensional single-atom catalysts (SACs) holds profound importance in the quest for efficient, stable, and economical alternatives to noble metals in hydrogen evolution (HER), oxygen evolution (OER), and oxygen reduction (ORR) reactions. By harnessing the remarkable tunability of transition metal (TM) active centers and their coordination environments coupled with the diversity of substrate materials, these catalysts present unprecedented opportunities for the design of highly stable and active electrocatalysts. This study offers a comprehensive exploration of the catalytic HER/OER/ORR activity in 207 ((TM-N_xH_xO_4–x)₃@g-C₁₂B₁₂N₁₂H₁₂) SACs, utilizing a seamless integration of density functional theory (DFT) and machine learning (ML). Twelve bifunctional OER/ORR catalysts with overpotentials exceeding Pt/IrO₂ were identified, with (Rh-N₂H₂O_2-V)₃@g-C₁₂B₁₂N₁₂H₁₂ and (Rh-N₁H₁O₃)₃@g-C₁₂B₁₂N₁₂H₁₂ monolayers emerging as standout trifunctional electrocatalysts due to their remarkably low HER overpotential. Through the Sure Independence Screening and Sparsifying Operator (SISSO) method, a clear relationship between intrinsic properties and activity was uncovered, with its acceptable prediction accuracy in intermediates adsorption affirmed. The constant-potential method further underscores the essential role of electric double-layer capacitance in modulating the kinetic barrier of the rate-determining step in them. We observed shifts in the Fermi level with changing electrochemical potential altering d-orbital occupation, highlighting the synergy between metal atomic orbitals and the band of substrate. With O₂ as the model adsorbate, we reveal the direct impact of these shifts on adsorption energies, uncovering a fascinating inversion of adsorption energies on Rh under varying electrochemical potentials. Such findings are driven by the filling of the d_xz orbital, which plays a pivotal role in stabilizing the O₂ π orbital and reshaping the electronic structure.