Layered Double Hydroxides-Derived Catalyst for Carbon Nanotube Growth: Understanding the Role of Molybdenum

Abstract

The design of multimetallic catalysts is a promising strategy for advancing the catalytic synthesis of carbon nanotubes (CNTs). Various element combinations have been explored, and among them, molybdenum (Mo) has been widely studied as a cocatalyst. However, conventional catalyst preparation methods often lead to nonuniform metal distribution, making it difficult to determine the role of Mo. Layered double hydroxides (LDHs), which provide a uniform distribution of metal cations, offer a promising alternative for controlled catalyst design. In this study, cobalt–magnesium–aluminum (CoMgAl) LDHs with varying molecular Mo content were synthesized to investigate the role of Mo in CNT growth. Phase analysis of Mo revealed that Mo2C forms beyond a specific Mo threshold, significantly enhancing CNT yield. Mo2C acts as a carbon reservoir, stabilizing Co particles and preventing deactivation. CNT synthesis was further examined using iron (Fe) and Fe–Co LDH systems, confirming that the role of Mo2C is independent of the active metal. The results demonstrate that Mo2C formation is essential for optimizing CNT growth, providing a deeper mechanistic understanding of Mo’s catalytic function. This study highlights the advantages of Mo species-intercalated LDH catalysts for achieving high-yield CNT synthesis and offers insights into multimetallic catalyst design.