This study investigates the sensing properties and mechanisms of LaF₃-Co₃O₄ nanorods for low-concentration methanol detection. Methanol is a characteristic gas that distinguishes between healthy individuals and lung cancer (LC) patients based on exhaled breath. The study synthesizes LaF₃-Co₃O₄ nanorods using a hydrothermal method to enhance methanol gas-sensing performance. 5 at% LaF₃-Co₃O₄ nanorods exhibit excellent methanol detection performance, including a wide linear detection range (0.2×10⁻⁶–5×10⁻⁶), a response value exceeding 4.0 for 1×10⁻⁶ methanol at 275 °C and 75% RH, long-term stability (maximum deviation within 15% over 2 weeks), and excellent selectivity. The performance enhancement is attributed to the special spinel structure of Co₃O₄, high ionic migration of F⁻ in LaF₃, larger specific surface area of 5 at% LaF₃-Co₃O₄ nanorods, and generated crystal defects. This work provides a novel route to prepare MOS composite materials for low-concentration methanol gas detection. Lung cancer is a leading cause of cancer-related deaths. Exhaled breath is a potential screening tool for LC diagnosis, with methanol as a potential biomarker. Previous studies have used two-phase composite materials for methanol detection, such as SnO₂-Pd-Pt-In₂O₃, Ag-LaFeO₃@ZnO-Pt, Sm₂O₃/ZnO/SmFeO₃, Co₃O₄-rGO, and Cd-doped Co₃O₄. These materials have demonstrated excellent gas-sensing performance for methanol but have limited detection capability for low-concentration methanol under high RH. Co₃O₄ is a typical spinel-phase face-centered cubic structure semiconductor material with a bandgap width ranging from 1.6 to 2.2 eV. LaF₃, a rare earth compound, has been applied in various fields, including molecular biological tagging and catalytic luminescence gas sensors. LaF₃ has been widely studied as a gas-sensing material since the end of the twentieth century. This study proposes to synthesize LaF₃-Co₃O₄ nanorods by hydrothermal and annealing treatment and assess the significance of different LaF₃ amounts on the characterization result and low-concentration methanol gas-sensing performance of Co₃O₄ nanorods. 5 at% LaF₃-Co₃O₄ nanorods exhibit better gas-sensing performance for low-concentration methanol under high RH environment. The excellent methanol sensing abilityThis study investigates the sensing properties and mechanisms of LaF₃-Co₃O₄ nanorods for low-concentration methanol detection. Methanol is a characteristic gas that distinguishes between healthy individuals and lung cancer (LC) patients based on exhaled breath. The study synthesizes LaF₃-Co₃O₄ nanorods using a hydrothermal method to enhance methanol gas-sensing performance. 5 at% LaF₃-Co₃O₄ nanorods exhibit excellent methanol detection performance, including a wide linear detection range (0.2×10⁻⁶–5×10⁻⁶), a response value exceeding 4.0 for 1×10⁻⁶ methanol at 275 °C and 75% RH, long-term stability (maximum deviation within 15% over 2 weeks), and excellent selectivity. The performance enhancement is attributed to the special spinel structure of Co₃O₄, high ionic migration of F⁻ in LaF₃, larger specific surface area of 5 at% LaF₃-Co₃O₄ nanorods, and generated crystal defects. This work provides a novel route to prepare MOS composite materials for low-concentration methanol gas detection. Lung cancer is a leading cause of cancer-related deaths. Exhaled breath is a potential screening tool for LC diagnosis, with methanol as a potential biomarker. Previous studies have used two-phase composite materials for methanol detection, such as SnO₂-Pd-Pt-In₂O₃, Ag-LaFeO₃@ZnO-Pt, Sm₂O₃/ZnO/SmFeO₃, Co₃O₄-rGO, and Cd-doped Co₃O₄. These materials have demonstrated excellent gas-sensing performance for methanol but have limited detection capability for low-concentration methanol under high RH. Co₃O₄ is a typical spinel-phase face-centered cubic structure semiconductor material with a bandgap width ranging from 1.6 to 2.2 eV. LaF₃, a rare earth compound, has been applied in various fields, including molecular biological tagging and catalytic luminescence gas sensors. LaF₃ has been widely studied as a gas-sensing material since the end of the twentieth century. This study proposes to synthesize LaF₃-Co₃O₄ nanorods by hydrothermal and annealing treatment and assess the significance of different LaF₃ amounts on the characterization result and low-concentration methanol gas-sensing performance of Co₃O₄ nanorods. 5 at% LaF₃-Co₃O₄ nanorods exhibit better gas-sensing performance for low-concentration methanol under high RH environment. The excellent methanol sensing ability