A comparative study of H 2 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. , Ti 3 C 2 T x and Ti 2 CT x ) loaded with Pd nanodots (NDs) prepared by photochemical reduction were investigated for room-temperature H 2 sensing. Interestingly, we found that Pd/Ti 2 CT x exhibited greatly enhanced sensitivity to H 2 , along with faster response and recovery rates compared to Pd/Ti 3 C 2 T x . The H 2 adsorption induced resistance change in Pd/Ti 2 CT x was higher than that of Pd/Ti 3 C 2 T x due to the more effective charge transfer at the heterointerface of Pd/Ti 2 CT 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.