Transforming monolayer Ti₃C₂Tx MXene into potassium titanate for room-temperature NO₂ sensing

Two-dimensional transition metal carbon nitrides (MXenes) are a prominent class of functional materials with significant potential for sensing applications. However, their conventional charge transfer mechanisms pose limitations for detecting nitrogen dioxide (NO 2 ). In this study, we successfully design-synthesized potassium titanate (KTO) nanoribbons by oxidizing and alkalizing monolayer Ti 3 C 2 T x MXene, targeting room-temperature NO 2 detection. The Ti 3 C 2 T x -derived KTO exhibited exceptional selectivity for NO 2 , achieving a remarkable response of 649.2 % for 50 ppm NO 2 , which is 550 times higher than that of the Ti 3 C 2 T x sensor (1.18 %). Additionally, the sensor demonstrated a detection limit as low as 5 ppb at room temperature, along with rapid response (1 s) and recovery times (2 s), and excellent linearity. Computational analysis showed that the abundant OH groups on the KTO surface contribute to strong selective adsorption (2.79 |eV|) and efficient electron transfer (0.91 |e|) for NO 2 . The unique proton conduction mechanism of KTO further reduced the activation energy for proton transport, enhancing NO 2 sensing performance. This study highlights the potential of Ti 3 C 2 T x -derived KTO nanomaterials for advanced room-temperature NO 2 detection and sensor technology development.