Multi-Single-Atom Catalysis in Cyclic Anthracene Frameworks: A Computational Pathway to Platinum-Competitive Hydrogen Evolution

This study employs density functional theory (DFT) to explore cyclic [3] anthracene (C[3]A) and its tetrameric analogue (4C[3]A) as molecular platforms for single- and multisingle-atom catalysis (SACs/multi-SACs) in electrochemical hydrogen evolution reaction (HER). By embedding isolated transition metal (TM) atoms (Co, Fe, Ni, Cu, Mo, Nb, Ru, and W) into the π-congested core, we engineer well-defined SAC and multi-SAC active sites─ranging from monometallic centers to homotrimeric (e.g., 3Mo, 3Ru) and heterometallic clusters (e.g., Nb–Mo–W, Ni–Mo–W) that are thermodynamically stable with high binding energy. Electronic structure analyses reveal that TM incorporation effectively narrows the HOMO–LUMO gap and redistributes frontier orbital density toward the Fermi level via synergistic hybridization between TM d-orbitals and the conjugated π-system. Charge distribution analysis confirms the electron-donating nature of the metals, enabling precise tuning of charge polarization across the framework. Remarkably, select SACs (C[3]A–Mo, C[3]A–Ni) and multi-SACs (C[3]A–3Ru, C[3]A–Ru–Mo–W) achieve near-optimal hydrogen adsorption Gibbs free energy (ΔGH), rivaling or exceeding Pt benchmarks. In contrast, their high oxygen evolution reaction (OER) overpotentials underscore HER selectivity. These results highlight the superior activity and stability of Mo-, Ni-, Ru-, and W-based C[3]A catalysts, establishing cyclic anthracene frameworks as a versatile platform for multi-SAC design and offering a pathway to efficient, tunable, and cost-effective electrocatalysts for sustainable hydrogen production.