Ambient methane detection remains constrained by humidity interference and insufficient sensitivity at room temperature. Compared with standalone Ti₃C₂T_x MXene, hetero-structured ZnO-pillared Ti₃C₂T_x MXene was engineered via a simple self-assembly method at room temperature, achieving breakthrough room-temperature moisture-tolerant CH₄ sensing at ppm level (< 1 ppm detection limit, response of 21.3% to 100 ppm CH₄ at 80% relative humidity (RH). Through in-situ electronic paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) spectroscopy, we demonstrate visible-light-driven hydroxyl radical (·OH) generation at ZnO/MXene interfaces in humid conditions. These radicals activate the catalytic conversion from CH₄ to CO₂ at reduced energy barriers, overcoming humidity poisoning by preferential H₂O dissociation, enhancing the sensing performance together with the increased hole concentration and the improved activity of oxygen species. This study not only paves a new way for designing MXene-based gas sensors adaptable to diverse environmental conditions, but also establishes a hetero-engineering paradigm for radical-mediated gas detection.

Real-time and sensitive detection of methane (CH₄) is vital to the safety of life and production due to the explosivity and greenhouse effect of methane. Currently, metal oxide semiconductor (MOS)-based chemiresistive sensors are considered as an effective approach for their low cost, highly tunable structures, and easy fabrication. However, disadvantages like high working temperature, low sensitivity, and unsatisfying selectivity limit their potential wide application. In order to achieve the goal of high-performance MOS-based methane sensors, in this review, from the basic mechanism of MOS-based gas sensing and the property of methane, possible strategies of improving methane sensing performances in multiple aspects have been summarized systematically, including sensitivity, selectivity, stability, and humidity resistance. Recent progress in the research and development of metal oxide semiconductor-based methane sensor technology is also surveyed in this review. Finally, the future trends and perspectives of MOS-based chemiresistive methane sensors are proposed.