Chemical Insights into the Design and Development of Face-Centered Cubic Ruthenium Catalysts for Fischer–Tropsch Synthesis

Abstract

Ruthenium is a promising low-temperature catalyst for Fischer-Tropsch synthesis (FTS). However, its scarcity and modest specific activity limit its widespread industrialization. We demonstrate here a strategy for tuning the crystal phase of catalysts to expose denser and active sites for a higher mass-specific activity. Density functional theory calculations show that upon CO dissociation there are a number of open facets with modest barrier available on the face-centered cubic (fcc) Ru but only a few step edges with a lower barrier on conventional hexagonal-closest packed (hcp) Ru. Guided by theoretical calculations, water-dispersible fcc Ru catalysts containing abundant open facets were synthesized and showed an unprecedented mass-specific activity in the aqueous-phase FTS, 37.8 mol·mol·h at 433 K. The mass-specific activity of the fcc Ru catalysts with an average size of 6.8 nm is about three times larger than the previous best hcp catalyst with a smaller size of 1.9 nm and a higher specific surface area. The origin of the higher mass-specific activity of the fcc Ru catalysts is identified experimentally from the 2 orders of magnitude higher density of the active sites, despite its slightly higher apparent barrier. Experimental results are in excellent agreement with prediction of theory. The great influence of the crystal phases on site distribution and their intrinsic activities revealed here provides a rationale design of catalysts for higher mass-specific activity without decrease of the particle size.

Surface‐supported cluster catalysis: Ensembles of metastable states run the show

“…It is clear that finding the correlation between catalyst morphology and catalytic performance is essential to designing new catalysts with enhanced efficiency. 14,74,[83][84][85][86][87][88][89][90] Hence, a major tool is global optimization, already discussed above, to be used for the finding of both the global and the accessible local minima of cluster catalysts. Second, one should be cautious when choosing the density functional in order to perform density functional theory (DFT) calculations on nanoclusters, because the relative energy of the cluster isomers is often dependent on the functional.…”

Ultra-Small Face-Centered-Cubic Ru Nanoparticles Confined within a Porous Coordination Cage for Dehydrogenation

“…Face-centered-cubic (fcc) noble-metal (Ru/Rh/Pd) NPs are more active catalytically than other close-packing structures 29 because the more active crystal surfaces are exposed in an fcc structure. 30 Recent research indicates that the rare fcc Ru NPs 31 are more efficient than common hcp Ru NPs, although the data available in the literature only apply to particle sizes > 3.0 nm. 32,33 Presumably, this could be extended to the size range < 3.0 nm.…”

A Linear Scaling Relation for CO Oxidation on CeO2-Supported Pd

“… 25 − 28 By correlating surface topology and catalytic performance, computational chemistry contributes to the design of new and improved catalysts. 29 − 32 Detailed knowledge of the structure of the catalytically active phase is essential for meaningful modeling of surface kinetics. The structure of CeO 2 -supported transition metals during CO oxidation has not been unequivocally determined, which explains the variety of surface models employed in computational modeling of these catalysts.…”