One-pot preparation of iron/alumina catalyst for the efficient growth of vertically-aligned carbon nanotube forests

Highlights: • One-pot fully wet method to prepare catalyst layers for the growth of VA-CNT arrays. • VA-CNT arrays with structure and quality comparable to those grown from standard PVD catalyst layers. • Concomitant formation of the Al-based buffer layer and Fe catalyst nanoparticles. -- Abstract: The catalytic growth of vertically-aligned carbon nanotubes (VA-CNTs) forest usually requires thin catalyst films deposited by multi-step and costly physical vapor deposition techniques. Here, we demonstrate that an efficient catalyst and its supporting layer for VACNT growth can be prepared by using a simple solution of Fe(NO₃)₃ and Al(NO₃)₃ deposited on silica in a single step. This process being much simpler and cheaper than existing preparation methods, it can easily be transferred to industry for the low-cost, thin and large-area coating of catalyst for VA-CNT growth. Our study shows that aluminum hydroxides preferentially react with the SiO₂ surface while iron hydroxides tend to form oxide or hydroxide nanoparticles, thus allowing preparation of an aluminum-based buffer layer with iron-based nanoparticles at its surface. Optimization of the Fe/Al ratio and salt concentrations yielded catalysts with performances similar to standard Fe/Al₂O₃ catalysts prepared by physical vapor deposition.