Controlled synthesis of uniform cup-stacked carbon nanotubes for energy applications

While carbon nanotubes (CNTs) have been widely used for various energy storage and conversion applications, controlled synthesis of CNTs with desired properties at low cost is still a challenge. Here we report our findings in the development of a controlled synthesis of uniform cup-stacked carbon nanotubes (CSCNTs) using a chemical vapor deposition (CVD) process assisted by carbon-encapsulated copper (Cu@C) catalyst. The use of Cu@C nanoparticles (~4.9 nm in diameter) facilitates the initial growth of CSCNTs protruded from the interior surface of porous carbon, producing CSCNTs with high yield. Uniform and small CSCNTs (with diameter of ~42 nm) of high purity are synthesized at an optimal temperature of 600 °C, which is lower than that typically demanded for synthesizing CNTs via CVD. The morphology and physical properties of the CSCNTs can be controlled and tuned by tailoring the carbon-encapsulated catalysts (e.g., the particle size or types of metal catalysts). To demonstrate the multifunctionalities of these CSCNTs, they were employed to catalyst support for fuel cells. Further, a variety of carbon materials have been synthesized using this method, paving the way for fabrication of nanostructured-carbon materials for various applications.