A Systematic Study on High-Yield Carbon Nanotube Synthesis over TiO2-Supported Catalysts: Effect of TiO2 Polymorphism and Support Particle Size

A systematic comparative study of the performance of multi-walled carbon nanotube (MWCNT) synthesis via chemical vapor deposition (CVD) was conducted. Special emphasis is placed on the role of TiO2 size and polymorphism as a catalyst support and how these influence the dispersion of the metal nanoparticles and their catalytic behavior. We present three distinct catalytic systems, supported on rutile particles, anatase particles, and anatase nanoparticles, each supporting dispersed Fe–Co nanoparticles anchored to their surfaces. In parallel, catalyst calcination and synthesis parameters, specifically temperature and reaction time, were systematically optimized to maximize carbon fixation yield. The maximum carbon fixation yields were 387% for Rutile/Fe–Co/MWCNT, 321% for Anatase/Fe–Co/MWCNT, and 673% for nanocrystalline Anatase/Fe–Co/MWCNT. These results indicate that the size of the TiO2 particles used as a catalyst support, the crystalline phase, and the experimental design for optimizing synthesis parameters play a crucial role in the yield of carbon nanotube synthesis. This suggests that a simple impregnation method can be used to fabricate a TiO2-supported metal catalyst and produce MWCNTs with high yield via CVD. This study reveals that catalyst engineering and design will pave the way for the synthesis of nanomaterials tailored to specific applications. The results position nanocrystalline TiO2 as a high-performance catalyst support under the experimental design used in this study for the MWCNT synthesis.