Mechanism and Kinetics of Oxidation Reaction of Aqueous Ti₃C₂T_<i>x</i> Suspensions at Different pHs and Temperatures

Abstract

Understanding the oxidation reaction of aqueous Ti₃C₂T_<i>x</i> MXene suspensions is very important for fostering fundamental academic studies as well as widespread industrial applications. Herein, we investigated the mechanism and kinetics of the oxidation reaction of aqueous Ti₃C₂T_<i>x</i> suspensions at various pH and temperature conditions. Through comprehensive analysis, the mechanism of the chemical oxidative degradation of aqueous Ti₃C₂T_<i>x</i> colloids was established. Chemical oxidation produces solid products such as TiO₂ and amorphous carbon as well as various gaseous species including CH₄, CO, CO₂, and HF. Additionally, our comprehensive kinetic study proposes that aqueous Ti₃C₂T_<i>x</i> dispersions are degraded via an acid-catalyzed oxidation reaction, where, under acidic conditions, the protonation of the hydroxyl terminal groups on the Ti₃C₂T_<i>x</i> flakes induces electron localization on titanium atoms and accelerates their oxidation reaction. In contrast, under basic conditions, the electrostatically alkali-metalized hydroxyl intermediates forming a bulky solvent cage results in less electron localization on titanium atoms, and thus retards their oxidative degradation.