Synergistic combination of 2-D MXene and MoO3 nanoparticles for improved gas sensing at room temperature

Abstract

MXene Ti3C2Tx (with 30% HF-etched, named Ti3C2Tx-30) plays a pivotal role in the substantial enhancement of the structural modification of molybdenum trioxide (MoO3). Additionally, as the surface MoO3 molecules come in contact with reducing gas moieties, they actively participate in gas sensing at room temperature. The percentage of Ti3C2Tx-30 in the MoO3 matrix was varied as 10%, 20%, and 40%, denoted as MM-10, MM-20, and MM-40, respectively. Structural analysis confirmed the composition of the basic elements, and evolution of TiO2 at higher percentage of Ti3C2Tx-30. Spectroscopy analysis shows the interactions between Ti3C2Tx-30 and MoO3, showcasing work functions of 6.91 eV, 6.75 eV, and 7.21 eV for MM-10, MM-20, and MM-40, respectively, confirming the MM-20 to be an optimum composition. When the samples were exposed to ammonia gas, MM-20 showed high response (93% for 100 ppm) at room temperature, with the response time ~ 10 s. As compared to bare MoO3 these samples showed ten-fold improvement. The excess electrons on the surface of Ti3C2Tx-30 facilitate the formation of O2- species, which also provides stability to the, otherwise-highly-reactive, MXene surface. These species actively react with ammonia molecules in the presence of adsorbed MoO3, thereby changing the resistance of the system. This can be a significant step towards imparting high gas sensitivity to metal oxides at room temperature via incorporation of optimum percentage of optimised Ti3C2Tx.