Impacts of Mo Promotion on Nickel-Based Catalysts for the Synthesis of High Quality Carbon Nanotubes Using CO₂ as the Carbon Source.

In recent years, the primary greenhouse gas (carbon dioxide) has caused a series of severe issues, such as global warming, climate change, etc. Therefore, CCU, CCS and CCUS technologies have been employed to reduce CO₂ emissions. Through our developed "chemical vapor deposition integrated process (CVD-IP)" using carbon dioxide as the carbon source, CO₂ could be catalytically activated and converted to high-value carbon nanotubes. In this work, methane and carbon dioxide has been applied to synthesize CNTs respectively to compare the difference between conventional CH4 CVD and CO₂ CVD-IP technology using Ni-Mo bimetallic catalysts. In the conventional CH4 CVD technology, the carbon productivity and the thermal stability of CNTs could be improved by changing the Mo content of the catalyst, the better catalytic performance 4% Mo catalyst is selected as model catalyst to apply to CO₂ CVD-IP technology. Moreover, when the weak oxidant CO₂ is the only carbon source in the CVD-IP technology, the carbon yield is 22% and the carbon productivity is 1.98 g/gcat. TG curves and Raman spectroscopy display that the CNTs with better thermal stability and higher degree of graphitization are achieved. TEM confirms that the fewer wall numbers and defects of CNTs are obtained. These characterizations suggest that the high quality CNTs could be achieved by CO₂ CVD-IP technology.