Catalytic growth of carbon nanotubes

We aim for a better understanding of the catalytic growth mechanism of carbon nanotubes (CNTs) through first principles calculation of binding energies and thus contribute to the development of the growth mechanism of CNTs with special properties. This activity was started in collaboration with Dr. Feng Ding, Professor Kim Bolton and Professor Arne Rosén at Chalmers.

The important role of the catalytic nanoparticles has previously been considered to be partly the decomposition of the raw material gas, for the delivery of carbon, and the seeding of CNTs, which requires the formation of graphitic domes on the particles. We were the first to show that an additional function is also important - to stabilize the growing end of the CNT, which is fulfilled for the magnetic metals (Fe, Co, Ni) commonly used to make CNTs. With our work, the phenomenological knowledge of the CNT growth mechanism can be extended with calculated bond strengths, which opens up a path for investigation of factors such as single-walled vs. multi-walled CNT growth, defect introduction energy, alloy catalysts, and the effect of impurities.

Our theoretical prediction of a carbon-metal bond strength, one of several criteria for CNT growth, has been proven experimentally in collaboration with Dr. Justin Holmes (University College Cork) by combining two catalytically inactive non-magnetic metals, one having excessively weak metal-carbon bonding (Cu, Pd) and one having excessively strong metal-carbon bonding (Mo, W) into active catalyst particle alloys (Mo/Cu, Mo/Pd, and W/Cu). The collaboration with Prof. Justin Holmes has also resulted in a study of the growth of N-doped CNTs. Our study of CNT growth contributes to an increased specific product control, which so far has not been possible and thus delayed the use of CNTs in the engineering context.

Publications

• Impact of training and validation data on the performance of neural network potentials: A case study on carbon using the CA-9 dataset
• Analytical modelling of single-walled carbon nanotube energies: the impact of curvature, length and temperature
• Length dependent stability of single-walled carbon nanotubes and how it affects their growth
• On the stability and abundance of single walled carbon nanotubes
• Establishing the most favorable metal-carbon bond strength for carbon nanotube catalysts
• Origin of the difference between carbon nanotube armchair and zigzag ends
• The importance of strong carbon-metal adhesion for catalytic nucleation of single-walled carbon nanotubes
• Calculating carbon nanotube-catalyst adhesion strengths
• Copper/molybdenum nanocomposite particles as catalysts for the growth of bamboo-structured carbon nanotubes
• Growth of carbon nanotubes from heterometallic palladium and copper catalysts
• Nitrogen-doped carbon nanotubes: Growth, mechanism and structure
• On the stability of single-walled carbon nanotubes and their binding strengths