Thermal Oxidation of Carbonaceous Nanomaterials Revisited: Evidence of Mechanism Changes

Kinetic data, for example, activation energy and reaction order, are crucial for the understanding of chemical reactions and processes. Here, we describe a novel method for obtaining kinetic data based on thermogravimetric measurements (TGA) that exploits in each measurement multiple successive isothermal steps (SIS). We applied this method to the notoriously challenging carbon combustion process for vastly different carbons for oxygen molar fractions between 1.4 % and 90 %. Our obtained apparent E_A values are within the wide range of results in the literature and vary in a systematic way with the oxygen partial pressure. The improved accuracy and large amount of obtainable data allowed us to show that the majority of experimentally obtained apparent data for apparent E_A are neither in a kinetic regime nor in a diffusion-controlled one but rather in a transition regime.