Construction of Spatial Effect from Atomically Dispersed Co Anchoring on Subnanometer Ru Cluster for Enhanced N2-to-NH3 Conversion

Simultaneously achieving a low activation barrier with weak binding of intermediates on a heterogeneous catalyst for the enhancement of catalytic performance under mild conditions remains a great challenge, especially for N-2-to-NH3 conversion. Herein, for the first time, we report a new strategy via integrating vacuum-freeze-drying and high-temperature pyrolysis technologies to design atomically dispersed Co deposits onto the surface of Ru tiny subnanoclusters (TCs). The special structure of this catalyst can generate a spatial effect and induce strong interelectronic interactions between Ru and Co. The outcome is simultaneous generation of the high-surface-unoccupied Co 3d charge and obvious upshifting of the Ru d-band center. With that, there is lowering of N-2 activation energy via strong electron sigma-donation and pi-backdonation between Ru and N-2 molecules. More importantly, our studies demonstrate that an appropriate Ru structure with tiny subnanoclusters rather than single Ru atoms or large Ru clusters could enable the repulsion to adsorption of the N-containing intermediates on the catalyst surface, resulting in weakening of the binding of NH3 and N(2)H(4)intermediates on the Co1Ru TC catalyst surface. In such a case, the scaling relation over Co1Ru TCs in NH3 synthesis was decoupled, and the developed Ba-promoted Co1Ru TC catalyst shows the highest NH3 synthesis rate (up to 21.90 mmol(NH3) g(-1) h(-1) at 360 degrees C and 3 MPa) among the Ru or Co-based catalysts ever reported.

Automated summary

This study presents a novel strategy to design a special catalyst for efficient NH3 synthesis from N2, where the strong interactions between Ru and Co play a crucial role. By integrating vacuum-freeze-drying and high-temperature pyrolysis technologies, the developed Co1Ru TC catalyst shows excellent catalytic performance.