Fe pre-deposition and H 2 O etching for thick VACNT growth on FeSiAl alloy

Vertically aligned carbon nanotube arrays (VACNTs) are attractive for various applications due to their excellent alignment, high purity, and large specific surface area. However, direct growth of VACNTs on bulk alloy substrates is hindered by two major challenges: low catalyst areal density resulting from unlimited Fe diffusion and rapid catalyst deactivation caused by amorphous carbon accumulation. Here, we report a synergistic strategy combining Fe pre-deposition and H2O-assisted etching to overcome these limitations on FeSiAl alloy bulk substrates. Experimental results show that under optimized conditions, VACNTs with a height of 0.5 mm are successfully grown on FeSiAl alloy bulk substrates. Mechanistic analysis reveals that Fe pre-deposition converts homogeneous nucleation into heterogeneous nucleation, dramatically increasing the catalyst particle density. The introduction of H2O establishes a dynamic etching-deposition equilibrium, effectively removing amorphous carbon and extending catalyst lifetime. This study provides a technical foundation for circumventing the reliance on complex and demanding processes in the fabrication of VACNTs with large thickness.