Co-Catalytic Solid-State Reduction Applied to Carbon Nanotube Growth

Abstract

We report on a new class of cocatalysts for the chemical vapor deposition of carbon nanotubes, where the cocomponent (Ta) acts as a solid-state reducing agent for the active catalyst (Fe). The cocatalytic FeTa system enables carbon nanotube growth without the need for a reducing gas atmosphere such as H2 or NH3. In situ X-ray photoelectron spectroscopy reveals that the tantalum (oxide) getters the oxygen from the iron (oxide) by a diffusive solid-state process, driven by the much larger affinity to oxygen of Ta compared to Fe. We suggest that this redox-based mechanism is applicable to a wide range of metal (oxide)/catalyst systems and relevant to rational catalyst design in general heterogeneous catalysis.