Liquid Nitrogen-Mediated Thermal Shock for Instantaneous Detachment of Multi-walled Carbon Nanotube Films from Substrates and Their Application in Supercapacitors

Pristine multiwalled carbon nanotube (MWNT) films have a range of important applications. Currently, vacuum filtration is the main method used to prepare MWNT films, which limits their large-scale production. Solvent evaporation is an alternative method used to fabricate MWNT films without the need of special equipment that does not limit the surface area of the film. However, after the evaporation process, the MWNT films adhere to the surface of the vessel. Traditional mechanical separation of MWNT films from substrates frequently leads to damage. Here, we show that thermal shock mediated by liquid nitrogen readily detaches the MWNT films from the substrate (evaluated on films of up to ca. 19.5 cm in diameter), attributed to the generation of a uniform shear force at the film/substrate interface and the uplifting force caused by the boiling nitrogen gas. The resulting nMWNT films are flexible and have low resistance and high surface areas. The nMWNT films were used to prepare inexpensive supercapacitors with a relatively high capacitance of 4.2 F g–1. The supercapacitors are stable with no decrease in capacitance observed even after prolonged operation in air.