Thermal degradation of native cellulose started at approximately 225.4 °C in an N2 atmosphere, while the CNCCr(NO3)3 product degradation began at ca. 238.2 °C. The increased thermal stability of CNCCr(NO3)3 might be attributed to the removal of defective crystalline cellulose, as evidenced above by XRD results. Nevertheless, the CNCH2SO4 showed a lower thermal stability (201.2 °C) than the untreated cellulosic material. This was presumably due to the attaching of sulfate groups on fiber surface during the hydrolysis step, which clearly reduced the activation energy for the degradation of nanocellulose product, making the nanomaterial less resistant to pyrolysis. Additionally, the lower degradation temperature of CNCH2SO4 could be due to the smaller fiber dimension, resulting in more surface areas exposed to the heat source and the partial disruptions of crystal structure compared to that of cellulose precursors . These findings are in good accordance with Kallel’s study , in which the nanocellulose isolated from garlic straw by H2SO4 hydrolysis started to degrade at a lower decomposition temperature (200 °C) than that of its starting material (220 °C). In summary, the introduction of the sulfated groups and massive decrement of molecular weight significantly decreased the thermal stability of CNC.