The effects of promoters on Ru nanoparticles (≥2 nm) catalysts for NH 3 synthesis have been extensively elaborated, but their roles on ultrasmall Ru nanoclusters (NCs, 1–2 nm) remain largely unknown and need to be further uncovered. Herein, a series of K-promoted MgO supported Ru NCs were synthesized and investigated for NH 3 synthesis. The addition of 5wt.%K onto Ru/MgO NCs leads to a significantly high NH 3 synthesis rate of 21.7 mmol NH3 g cat −1 h −1 at 400 °C and 0.2 MPa, close to the thermodynamic equilibrium. Out studies reveal that anchoring K onto Ru NCs can increase the electron density and cause an upshift of the d -band center of Ru entities. Moreover, the addition of K regulates the hydrogen affinity and accelerates the migration of hydrogen from the Ru NCs surface to MgO support, which is crucial in avoiding the hydrogen poisoning effect on Ru NCs. With the synergistic effect of the Ru NCs sites bridged by H-spillover, makes the K-mediated Ru/MgO NCs catalysts efficient for NH 3 synthesis at mild conditions.
Nanozymes have fascinated increasing attention in the field of artificial enzyme . Designing an ideal nanozyme usually requires a synergic advantage of reasonable nanostructures and large specific surface area for ensuring excellent mimicking-enzyme catalytic activity . Here we report a CuS nanozyme with hollow nanocube structure (h-CuS NCs), which has a large surface area of 57.84 m 2 g −1 , and thus realizes excellent mimicking-enzyme catalytic activity . Expectedly, our directed design of h-CuS NCs nanozymes has an affinity for H 2 O 2 of 0.94 mM, which is outstanding among the state-of-the-art Cu-based nanozymes. Furthermore, this nanozyme acts as a multifunctional catalyst to induce luminol chemiluminescence and oxide 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 , and displays distinguished electrocatalytic activity to glucose oxidation . More intriguingly, the nanozyme can produce a promising photothermal effect under the illumination of near-infrared light. This work will provide a prototype for rational design of distinct nanostructures as multifunctional nanozymes in the area of electrochemical sensing, mimicking-enzyme catalytic biosening and cancer therapy.
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