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-NH 3 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 “σ-donation and π-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 NH 3 and N 2 H 4 intermediates on the Co 1 Ru TC catalyst surface. In such a case, the scaling relation over Co 1 Ru TCs in NH 3 synthesis was decoupled, and the developed Ba-promoted Co 1 Ru TC catalyst shows the highest NH 3 synthesis rate (up to 21.90 mmol NH 3 g –1 h –1 at 360 °C and 3 MPa) among the Ru or Co-based catalysts ever reported.