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.