Due to their strength, electrical conductivity and surface area, carbon nanotubes (CNTs) are increasingly finding application in advanced electronics, energy-storage installations, batteries, medical devices, separation processes and much more. A new CNT production technology developed by the SPICE division of Volta Energy (Toronto, Ont. Can.; www.voltaenergy.ca) uses methane as its only input and creates no CO2 emissions. “Under controlled pyrolysis conditions (450–900°C) and ambient pressure, methane is catalytically decomposed using Volta Energy’s proprietary catalyst. This reaction splits methane into two primary products: CNTs and hydrogen gas. The catalyst plays a critical role in facilitating the selective growth of CNTs while suppressing undesired carbon byproducts. The hydrogen co-produced in this reaction can be captured and utilized as a clean energy source, enhancing the sustainability of the process,” explains Fenglou Zou, Volta Energy’s principal research scientist.
Source: Volta SPICE
Unlike typical commercial CNT processes, no external hydrogen feedstock is required, the operating temperatures are more mild and there is an opportunity to utilize renewable feedstocks, such as upgraded biogas. By making adjustments to the process temperature and catalyst composition, CNT structure, including diameter, length, defects and shape, can be precisely controlled. “Transmission electron microscopy analysis confirmed minimal amorphous carbon formation, demonstrating the process’s high selectivity for CNTs. Additionally, by employing a specialized catalyst variant, the system can produce unique carbon nanotube ball (CNB) structures — a morphology with potential advantages in certain applications,” notes Zou. The process is solvent-free and produces no byproducts, other than hydrogen gas and a very small volume of short-chain hydrocarbons, both of which Volta Energy says “can be recycled and utilized to offset the thermal energy requirements of the process, creating an energy-efficient closed-loop system.”
The Volta SPICE team has validated the process in numerous laboratory-scale demonstrations, and scaleup is currently underway with a pilot unit producing 50-g batches expected later this year. As part of a strategic partnership with battery technology company MakeSens (Calgary, Alta., Can.; www.makesens.ca), Volta Energy will supply its CNTs for MakeSens’ production of advanced silicon anodes. “The integration of CNTs into Si-based anodes delivers critical performance enhancements, including improved electrical conductivity and mechanical strength and mitigating the side effect of battery swelling,” adds Gursaran Singh, who is leading the SPICE division.