Sensing properties and mechanisms of LaF₃–Co₃O₄ nanorods for low-concentration methanol detection

Methanol is one of the characteristic gases that distinguish between healthy individuals and lung cancer (LC) lesions in exhaled human breath. Its concentration in exhaled breath is generally below one part per million (1×10⁻⁶). The second-phase composite is widely regarded as one of the methods to improve the gas-sensing performance of metal oxide semiconductor (MOS) materials. In this study, LaF₃–Co₃O₄ was synthesized by a simple hydrothermal method to enhance its low-concentration methanol gas-sensing performance. 5 at% LaF₃–Co₃O₄ nanorods exhibited excellent methanol detection performance, including a wider linear detection concentration range (0.2×10⁻⁶–5×10⁻⁶), a response value exceeding 4.0 for 1×10⁻⁶ methanol at 275 °C and 75% relative humidity (RH), long-term stability (maximum deviation within 15% over 2 weeks), and excellent selectivity. The mechanism of performance enhancement was studied using various techniques, and density functional theory. The special spinel structure of Co₃O₄, the high ionic migration of F⁻ in LaF₃, the larger specific surface area of 5 at% LaF₃–Co₃O₄ nanorods, and the generated crystal defects all explain the excellent methanol gas-sensing property. This work provides a novel route to prepare MOS composite materials for low-concentration methanol gas detection.