Surface functionalization tuned optical and thermal properties of Ti₃C₂ MXene for enhanced photothermal conversion

Ti₃C₂T₂ MXenes (where T represents bare atoms, F atoms, OH groups or O atoms) have shown significant potential for photothermal conversion applications. However, the effects of surface terminations on the thermal and optical properties remains not fully understood. In this study, we have specifically examined the impact of electron-phonon scattering and intra-band transitions on the thermal and optical properties of Ti₃C₂T₂ MXenes. The ab initio calculations reveal that the introduction of F and OH groups nearly make the thermal conductivity triple, primarily due to enhanced electronic thermal conductivity resulting from changes in the electronic structure. The introduction of O atoms also enhances thermal conductivity by up to double. Furthermore, Ti₃C₂ exhibits notable sunlight absorptivity of up to 15.65 %, which is caused by the dense packed electronic states near the Fermi level, and Ti₃C₂F₂ shows excellent near-infrared light absorption of up to 19.36 %. These results suggest that surface functionalization can significantly improve the specific photothermal performance of Ti₃C₂ MXenes. However, Ti₃C₂O₂ exhibits significantly reduced light absorption, so the introduction of O atoms should be minimized in photothermal applications. This work provides valuable insights into the mechanism that tailored surface functionalization can optimize the photothermal properties of Ti₃C₂ MXenes.