A novel synthesis route for bimetallic CoCr–MCM-41 catalysts with higher metal loadings. Their application in the high yield, selective synthesis of Single-Wall Carbon Nanotubes

We present a study on CoCr–MCM-41 catalysts with stable nm-sized particles. The focus is their promoting effect on the synthesis of Single-Wall Carbon Nanotubes (SWNT).Bimetallic CoCr–MCM-41 catalysts were synthesized by combined grafting and incorporation of metals in the framework. This synthesis allowed an increase in the maximum metal loading in the MCM-41 framework while maintaining nm-sized Co particles stable in high-temperature reactive environments. The SWNT yield was increased by more than 100% from the Co–MCM-41 catalyst.Cobalt is responsible for SWNT nucleation. The role of chromium is to anchor small cobalt particles during reduction and prevent their sintering into large unreactive particles. A larger fraction of the cobalt in the bimetallic catalysts becomes available for the SWNT synthesis when compared to the monometallic one, leading to a significant yield increase. Another effect of the addition of Cr was a shift of the SWNT diameter distribution to smaller nanotubes.

Graphical abstractCharacterization of SWNT synthesized on various catalytic systems: Co grafted on MCM-41 (CogMCM-41), Co incorporated on MCM-41 (Co–MCM-41), Cr grafted on Co–MCM-41 (CrgCo) and Co grafted on Cr–MCM-41 (CogCr). Left – resultant SWNT yield. Right – Resonant Raman Spectroscopy of SWNT.Figure optionsDownload full-size imageDownload high-quality image (97 K)Download as PowerPoint slide