Exfoliation behavior and superior photothermal conversion performance of MXenes beyond Ti3C2T

Two dimensional transition metal carbides (MXenes) have attracted significant interest due to their unique layer structure, chemical diversity and superior physiochemical performances. However, most studies have focused on Ti3C2Tx, and the synthesis process and photothermal conversion capability of other MXenes remain unclear. In this work, we have systematically investigated the exfoliation behavior of six different MXenes, including mono-transition-metal (Ti3C2Tx, V2CTx, and Nb2CTx) and double-transition-metal (TiVCTx, TiNbCTx, and NbVCTx) MXenes derived from MAX phases, integrated with their photothermal conversion performance by combining experimental and theoretical studies. The phase, morphology, composition and surface groups of the different MXenes have been analyzed using XRD, SEM, XPS, and HRTEM techniques. Our results indicate a systematic variation in etching difficulty from difficult to easy, as Nb2AlC > NbVAlC > V2AlC > TiNbAlC > TiVAlC > Ti3AlC2, which correlates with the chemical composition and etching duration. Furthermore, the exfoliation factor m from density functional theory calculations reveals that the bond energies of M−A bonds are much weaker than M−X bonds in MAX phases, which agrees well with the experimental results. Interestingly that, all the obtained MXenes exhibit remarkable photothermal conversion performance with fast response, where the MXenes beyond Ti3C2Tx, such as V2CTx, NbVCTx, Nb2CTx, TiVCTx, and TiNbCTx, display higher saturation temperature of 95, 88, 81, 78, and 71 °C, respectively, than that of Ti3C2Tx (65 °C). These findings could potentially facilitate the efficient design and development of diverse MXene materials with outstanding photothermal conversion performance for applications in wearable devices, biomedical technology and solar water desalination.