Ni–Mo and Co–Mo alloy nanoparticles for catalytic chemical vapor deposition synthesis of carbon nanotubes

Highlights: • Thermal decomposition of the ε-Keggin-type polyoxomolybdate clusters Mo₁₂O₂₈(μ₂-OH)₁₂{Ni(H₂O)₃}₄ and Mo₁₂O₂₈(μ₂-OH)₁₂{Co(H₂O)₃}₄ produces NiMoO₄ and CoMoO₄ phases. • The NiMoO₄ and CoMoO₄ phases are converted in alloys with a metal ratio of 1:1. • The Ni–Mo and Co–Mo alloy nanoparticles catalyze a CCVD growth of carbon nanotubes. - Abstract: Here, we show for the first time a catalytic chemical vapor deposition (CCVD) synthesis of carbon nanotubes (CNTs) using polyoxomolybdate clusters Mo₁₂O₂₈(μ₂-OH)₁₂{Ni(H₂O)₃}₄ and Mo₁₂O₂₈(μ₂-OH)₁₂{Co(H₂O)₃}₄ as a source of catalyst nanoparticles. X-ray diffraction analyses indicated that the products of thermal decomposition of the clusters contain NiMoO₄ and CoMoO₄ phases, which are converted into Ni–Mo and Co–Mo alloys at 900 °C in hydrogen environment. High-resolution transmission electron microscopy in combination with energy-dispersive X-ray spectroscopy confirmed the CNT growth from bimetallic nanoparticles. Synergism between two metals in an alloy resulted in large-scale production of non-bundled few-walled CNTs with narrow diameter distribution and high quality