Engineering Heterogeneous Dual-Coordination Environments for Single-Atom Nickel Catalysts: A Synergistic Strategy to Enhance Selective Hydrogenation

Single-atom catalysts with precisely defined active sites have garnered significant attention for heterogeneous reaction, yet their inherent limitation of weak linear scaling relationships between intermediate adsorption energies substantially hampers multireactant conversion efficiency. Herein, we develop a synergistic dual-coordination single-atom Ni catalyst (Ni₁-S₆/Ni₁-Mo₂) by utilizing the ordered basal plane and abundant edge sulfur vacancies in ultrathin MoS₂ layers. The obtained catalyst demonstrates the synergistic catalytic functions: the Ni₁-Mo₂ species facilitate hydrogen activation with an ultralow energy barrier and enable dynamic hydrogen spillover, while the Ni₁-S₆ center directs the heterolytic H^δ- to transfer toward selectively bonded di-σ acetylene, favoring ethylene formation rather than by-products (ethane and green oil). The synergistic dual-coordinated Ni sites achieve the breakthrough performance in selective acetylene hydrogenation involving 91.9% selectivity at full conversion under mild conditions and long-periodic stability originating from structural maintenance and excellent resistance to coking. Density Functional Theory (DFT) calculations and in situ characterizations confirm that the synergetic effect originates from edge vacancy-mediated electron-enriched Ni species enhancing H₂ activation and electronic interaction between Ni and S in plane modulating the adsorption type of C≡C bond.