Beyond metal-centric catalysis in dual-atom catalysts: bridge N sites drive dehydrogenation via Co-Cu synergy

Dual-atom catalysts (DACs) have emerged as a promising platform for tailoring the electronic properties of isolated metal sites in (de)hydrogenation reactions. However, the molecular-level identification of true active sites in such systems remains elusive. Using first-principles calculations, we reveal an unconventional active site in CoCuN₆-C DAC for HCOOH decomposition: the bridge nitrogen atoms between Co and Cu dual metal centers, rather than the metal sites themselves, serve as the dominant adsorption sites for *H species. Crucially, Cu incorporation induces dual synergistic effects, shifting the Co d-band center toward the Fermi level and activating the electronic states of bridge N atoms through metal-to-N charge transfer. Compared to conventional CoN₄-C catalysts, the optimized H adsorption strength at both Co and N sites in CoCuN₆-C achieves an ideal balance between HCOOH dehydrogenation (to HCOO* + *H) and subsequent *H desorption for H₂ evolution. Most strikingly, we identify an NH configuration formed via N-site hydrogenation as the genuine catalytic hotspot, exhibiting substantially enhanced activity over pristine N sites. This study challenges the conventional metal-centric view of DAC catalysis, demonstrating that coordinated heteroatoms can be strategically engineered as primary active sites through atomic-level metal doping, and making DACs promising catalysts for (de)hydrogenation reactions.