A comparative study of H₂ sensing performance of stoichiometric polymorphs of titanium carbide MXenes loaded with Pd nanodots

Although titanium-based MXenes have been widely reported for gas sensing, the effect of crystal stoichiometric variations on the sensing properties has been rarely reported. Herein, stoichiometric polymorphs of titanium carbide MXenes (i.e., Ti₃C₂T_x and Ti₂CT_x) loaded with Pd nanodots (NDs) prepared by photochemical reduction were investigated for room-temperature H₂ sensing. Interestingly, we found that Pd/Ti₂CT_x exhibited greatly enhanced sensitivity to H₂, along with faster response and recovery rates compared to Pd/Ti₃C₂T_x. The H₂ adsorption induced resistance change in Pd/Ti₂CT_x was higher than that of Pd/Ti₃C₂T_x due to the more effective charge transfer at the heterointerface of Pd/Ti₂CT_x, which was confirmed by shifts of binding energies and theoretical calculation results. We hope this work could be helpful to design more high-performance MXene-based gas sensors.