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

Abstract

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 N2-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 N2 activation energy via strong electron “σ-donation and π-backdonation” between Ru and N2 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 N2H4 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 mmolNH3 g–1 h–1 at 360 °C and 3 MPa) among the Ru or Co-based catalysts ever reported.

Synergistically enhanced single-atomic site catalysts for clean energy conversion

“…For example, Jiang et al designed an atomically dispersed Co deposit onto the surface of Ru tiny sub-nanoclusters (Co 1 Ru TCs). 43 According to the EPR spectra, the g value (2.56) of Co 1 Ru TCs could be ascribed to the unpaired electron in the orbital of Co II and Ru III . To explore the effect of electronic interaction between the atomically dispersed Co and Ru clusters, dual atomically dispersed Co and Ru (denoted as Co 1 Ru DAs) were also prepared.…”

“…For example, Jiang et al reported a new strategy by integrating vacuum-freeze-drying and high-temperature pyrolysis technologies to design atomically dispersed Co deposits onto the surface of Ru clusters. 43 Cheng et al developed a universal and facile room temperature impregnation strategy to construct a Ru atomically dispersed catalyst with Ru-C 5 single atoms and Ru oxide nanoclusters ($1.5 nm), which could also be extended to prepare Ir, Rh, Pt, Au, and Mo atomically dispersed catalysts. 34 In addition, atomically dispersed metal sites on carbon, especially those with M-N-C coordination, have demonstrated excellent catalytic activities both experimentally and theoretically.…”

Facile Synthesis and High‐Value Utilization of Ammonia

“…Furthermore, atomically dispersed Co atom anchored on subnanometer Ru cluster (Co 1 Ru TC) catalyst was developed to overcome the scaling relation and enhance NH 3 synthesis (Figure 6). [ 7 ] The special structure of this catalyst generates a spatial effect and induces strong interactions between Ru and Co, resulting in the simultaneous generation of high‐unoccupied Co 3d orbitals and obvious upshifting of Ru d‐band center. As a consequence, the activation energy of N 2 was lowered via strong electron “σ‐donation and π‐backdonation” between Ru and N 2 molecules.…”

“…Thus, we could propose a “zero‐carbon” circular economy roadmap by a “renewable energy‐green hydrogen‐green ammonia‐hydrogen energy” route, as shown in Figure 1. [ 6‐7 ] The key is to develop environmentally friendly, and energy‐saving technologies of NH 3 synthesis and utilization as the substitute to avoid aggravating the consumption of fossil fuels.…”

Molecular‐Level Insights into the Notorious CO Poisoning of Platinum Catalyst

“…Because the valence electrons close to the Fermi level mainly contribute to the d states, the shift of valence band toward Fermi levels implies the upward shift of 5d-band center from Pt-b1 to Pt-b6. [39][40][41][42] Moreover, quasi in situ XPS measurements were conducted to trace the evolution of Pt electronic structure in Figures S48 and 5c. Obviously, both the binding energy and percentage of Pt species remain almost unchanged until the reaction temperature reaches 150 °C, while further raising temperature results in the partial oxidation and reduction of Pt for CO-TOX and CO-PROX, owing to the oxidized and reduced atmosphere, respectively, which were further verified by the in situ ultraviolet-visible (UV/Vis) spectra in Figures S49 and S50.…”