Electronic Structure of Bimetallic CoRu Catalysts Modulates SWCNT Nucleation

TL;DR

This study uses quantum chemical simulations to explore how Ru loading in CoRu catalysts affects SWCNT nucleation, revealing that Ru modulates electronic structure and catalytic activity during the process.

Contribution

It demonstrates how Ru influences SWCNT nucleation by altering the electronic structure and surface chemistry of CoRu catalysts, a novel insight into catalyst design.

Findings

Ru decreases catalytic efficiency and impedes C-H activation.

Longer-lived reactive intermediates are stabilized on the catalyst surface.

Ru's influence is indirect, affecting electronic structure rather than direct catalytic activity.

Abstract

Nucleation of single-walled carbon nanotubes (SWCNTs) via chemical vapour deposition of methane on CoRu bimetallic nanoparticles is simulated using quantum chemical molecular dynamics. By varying the Ru loading in the catalyst, we show that Ru decreases catalytic efficiency; C-H bond activation is impeded, key reactive intermediate species become longer-lived on the catalyst surface, and longer carbon chains are stabilised through the earliest stages of SWCNT nucleation. Analysis of the CoRu nanoparticle structure during the CVD process shows that this influence of Ru is indirect, with the catalyst adopting Ru-Co core-shell or segregated structures throughout nucleation, and Co exclusively driving the catalytic decomposition of the methane precursor. We show that the influence of Ru occurs via the electronic structure of the catalyst itself, by lowering the Fermi level of the catalyst due to lower energy 4d/5s states, in a manner consistent with d-band theory.