Multimetallic Single-Atom Catalysts for Hydrogen Evolution: Symmetry-Guided Discovery and Cooperative Site Effects

Designing multimetallic single-atom catalysts for hydrogen evolution requires identifying favorable metal arrangements within a large composition space and understanding how auxiliary metals regulate hydrogen binding. Here, we have used (M1, M2, M3, M4)–N4/G catalysts on nitrogen-doped graphene as a case study to develop a symmetry-guided screening strategy. By incorporating approximate remote-site exchange symmetry into composition grouping and hydrogen adsorption free-energy prediction, this strategy has reduced 57120 ordered arrangements to 28560 compositions while preserving chemical distinctions among adsorption-center, neighboring, and remote sites. A symmetry-aware ensemble trained on density functional theory (DFT) data for 995 compositions has identified (Co, Cu, Fe, Zn)–N4/G with a ΔGH of -0.0015 eV. Electronic-structure analysis of Co-centered compositions has revealed the orbital contributions to cooperative effects of neighboring and remote metals on local bonding. The neighboring metal alters the relative s/p and d contributions to bonding changes, determining whether the same remote substitution enhances or suppresses adsorption-induced Co–N bond weakening. These findings guide the joint selection of neighboring and remote metals in precious-metal-free hydrogen evolution catalysts.