Synergistic Catalysis of Single-Site Rhenium and Ruthenium Nanoclusters for Ammonia Synthesis under Mild Conditions

The development of high-efficiency NH3 synthesis catalysts under mild conditions is urgently required to alleviate the excessive energy consumption and carbon emissions in traditional Haber–Bosch processes. Although Ru-based catalysts show considerable potential, their catalytic activity is often severely constrained by hydrogen poisoning caused by strong H2 adsorption. Herein, we report the fabrication of a Ba/0.1Re–Ru/AC catalyst through the strategic integration of single-atom Re species into a conventional Ba/Ru/AC framework. Notably, the Ba/0.1Re–Ru/AC catalyst exhibits a high NH3 synthesis rate of 65.1 mmol g–1 h–1 at 400 °C and 1 MPa. Mechanistic investigations reveal that single-atom Re species function as a supplementary active site for H2 adsorption and activation. The incorporation of Re also facilitates H-spillover over the catalyst surface, which effectively alleviates the competitive adsorption between H2 and N2 on Ru sites and consequently mitigates hydrogen poisoning on Ru nanoclusters. Concurrently, the incorporation of single-atom Re modulates the defect density of the support and promotes the creation of additional strong Lewis basic sites. These structural changes induce a strong electronic metal–support interaction (EMSI) effect, which specifically tunes the electronic structure of the Ru nanoclusters. This synergistic interplay between single-atom Re sites and Ru nanoclusters establishes a compelling paradigm for the rational design of highly efficient NH3 synthesis catalysts.