Engineering highly graphitic carbon quantum dots by catalytic dehydrogenation and carbonization of Ti3C2Tx-MXene wrapped polystyrene spheres

The catalytic dehydrogenation of Ti3C2Tx-MXene nanosheets induced by their surface terminating C-Ti-O group has attracted tremendous interests in the fabrication of unsaturated organics and carbon materials. Herein, the highly graphitic carbon quantum dots (CQDs) were synthesized by pyrolyzing cationic polystyrene (CPS) spheres which were wrapped by Ti3C2Tx-MXene nanosheets. The morphological features and fluorescent properties of the as-prepared CQDs were characterized and the growth mechanism of CQDs was proposed. In this unique hybrid model, Ti3C2Tx-MXene exhibited high efficiency in catalyzing dehydrogenation and carbonization of CPS to highly graphitic CQDs at a relatively low pyrolysis temperature of 410 °C. During the pyrolysis, Ti3C2Tx-MXene shell acted as a closed barrier to retain the volatilization of degradation products of CPS and promote their diffusion into the MXene interlayers. Simultaneously, lots of CPS degradation products were adhered to the surface of Ti3C2Tx-MXene nanosheets, where the dehydrogenation was carried out by the C-Ti-O catalytic active sites. Eventually, they were carbonized to highly graphitic CQDs with excellent photoluminescence behavior. This work provides a facile strategy to convert polystyrene matrix into graphitic carbon-based material, which helps to develop the catalytic carbonization mechanism of MXene/polymer nanocomposites.