Synthesis of boron-doped carbon nanotubes by thermocatalytic decomposition of ethanol using a floating catalyst chemical vapor deposition method: kinetic study

A kinetic study was conducted to define experimental rates of reaction for the production of boron-doped carbon nanotubes (BCNTs) using a floating catalyst chemical vapor deposition technique. Here, boric acid (boron) and ferrocene (catalyst) dissolved in ethanol (carbon) were used as precursors. As a part of the kinetic study, the synthesis temperature, partial pressure of the boron precursor, catalyst precursor, and carbon source were studied in detail. A seven step reaction mechanism and a rate expression were proposed. Using the developed reaction kinetic model, we proposed the irreversible adsorption of ethanol followed by abstraction of hydrogen from the ethyl group adsorbed on iron nanoparticles to be the rate-controlling step. From the Arrhenius plot, in the temperature range of 750–950 °C, the activation energy for the overall reaction was found to be 68.9 kJ mol−1. It was found that an increase in synthesis temperature is responsible for the reduction in boron content (at%) and also defect density. Various spectroscopic and microscopic analyses were performed to evaluate the properties, quality, and purity of BCNTs formed.