Co3O4@PEI/Ti3C2Tx MXene nanocomposites for a highly sensitive NOx gas sensor with a low detection limit

Abstract

A simple noncovalent chemical approach and hydrothermal method were used for effectively riveting Co₃O₄ nanocrystals to branched polyethylenimine (PEI) functionalized Ti₃C₂T_x MXene sheets to fabricate Co₃O₄@PEI/Ti₃C₂T_x MXene composites. Co₃O₄ nanoparticles as active center components were uniformly dispersed on Ti₃C₂T_x MXene with high specific surface area and abundant functional groups to form a heterogeneous structure. PEI, as a channel for electron transfer, effectively improved the interaction between Ti₃C₂T_x MXene and Co₃O₄. The diffusion capacity of NO_x molecules and the electron transmission efficiency at the interface between adsorbed molecules and the surface of the material were improved, which contributed to the sensing performance of the material. Meanwhile, the highest sensing response to NO_x gas was seen in the Co₃O₄@PEI/Ti₃C₂T_x MXene composites with 2.4 mg addition of Ti₃C₂T_x sheets (CoPM-24). CoPM-24 exhibited a response and response time of 27.9 and below 2 s for NO_x gas at room temperature under humidity of 26%. Moreover, CoPM-24 also showed excellent selectivity, repeatability and a low experimental detection limit (30 ppb) for NO_x gas. Thus, the Co₃O₄@PEI/Ti₃C₂T_x composites are potential high-sensitivity NO_x gas sensor candidates.