Effects of ammonium chloride on the yield of carbon nanofiber aerogels derived from cellulose nanofibrils

Abstract

Carbon nanofiber (CNF) aerogels are a new class of advanced materials that have many potential applications in the energy and environmental sectors. However, some CNF aerogels consist of materials derived from fossil-fuels and energy-intensive production processes. For the successful industry-scale applications of carbon aerogels, the development of large-scale production methods with a smaller environmental footprint is required. Cellulose is a promising alternative material as a precursor of CNF aerogels, due to its renewability, high carbon content, and carbon neutrality. However, the low yield of CNF aerogels from the pyrolysis of cellulose nanofiber (CellNF) aerogels hinders their practical applications. To increase the yield of CNF aerogels from the pyrolysis of CellNF aerogels, we investigated the use of ammonium chloride (NH4Cl) as a carbonization promoter. The influence of the amount of NH4Cl, pyrolysis temperature, and method of adding NH4Cl to the cellulose precursor were systematically studied. Drastic improvements were observed in the yields of CNF aerogels, by 141–446% at 600 °C and 118–225% at 800 °C of pyrolysis, with the addition of NH4Cl (0.5–1.5 NH4Cl/CellNF weight ratio). The morphology, chemical and crystalline characteristics, microstructure, and porosity of CNFs in the aerogels were not affected by the addition of NH4Cl.