Thermal-Oxidative Degradation Kinetics of Salen-Type Schiff Base-Functionalized Graphene Oxide and Its Reduced...

Graphene oxide (GO) was covalently functionalized with a salen-type Schiff base (SB) and its reduced analogue (rSB) to obtain cGO-SB and cGO-rSB. The thermo-oxidative decomposition behavior was investigated by thermogravimetric analysis (TGA/DTG) in flowing air from 45 to 800 °C at a heating rate of 5 °C/min. The second and third mass-loss stages were evaluated using the Coats-Redfern (C-R) model-fitting approach to obtain apparent kinetic parameters. Functionalization-reduced moisture-related mass loss and increased the integral procedure decomposition temperature index (IPDT) from 406.9 °C for GO to 463.2 °C for cGO-SB and 489.7 °C for cGO-rSB. In the second stage, reaction-order models provided suitable apparent descriptions, with F2 used as a representative model for comparison, while F2.5 remained competitive for GO and cGO-SB. The F2-based apparent activation energy decreased from 90.27 kJ/mol for GO to 50.74 and 42.80 kJ/mol for cGO-SB and cGO-rSB, respectively. In the third stage, carbon framework oxidation/combustion involved reaction-order and diffusion-related contributions. The activation thermodynamic descriptors (ΔH, ΔS, and ΔG) further supported the comparative assessment of oxidative stability across the three structurally related GO derivatives under identical conditions examined here experimentally. Overall, the combined TGA/DTG, IPDT, apparent kinetic, activation thermodynamic, and initial X-ray Photoelectron Spectroscopy (XPS) results indicate that a coupling motif, oxygen/nitrogen functionality, and reduction degree collectively regulate the thermo-oxidative degradation of GO-based materials.