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

High Resolution Image Download MS PowerPoint Slide 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 (Δ H, Δ S, and Δ G ) 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.