Spatially Binary Single-Atom La and Mn Sites on Co₃O₄ for Enhanced Triethylamine Sensing

Triethylamine (TEA) is a hazardous volatile organic compound, and its sensitive and selective detection remains challenging due to the constraints of isolated strategies for improving gas-sensing properties. Herein, we report hollow Co₃O₄ nanotubes with spatially binary single-atom Mn³⁺ and La³⁺ sites, which synergistically modulate the electronic structure and defect density to enhance TEA sensing. STEM imaging revealed the spatially binary single-atom Mn³⁺ and La³⁺ sites on Co₃O₄ nanotubes. Aberration-corrected STEM confirms Mn³⁺ substitutional doping within the lattice and atomically La³⁺ anchoring at the surface. With a Co²⁺/Co³⁺ ratio of 0.95 and a 2.2-fold rise in oxygen-vacancy density (31.0%), spatially distributed La&Mn-Co₃O₄ couples Mn-driven electronic activation with La-mediated chemisorption to achieve a 3.4-fold higher response to 100 ppm TEA and a 20 °C lower operating temperature than pristine Co₃O₄, along with a 1.5-fold improvement in selectivity index. Density functional theory with the Hubbard U correction (DFT + U) simulation indicates that Mn³⁺ introduces mid-gap states and enhances O 2p spin polarization, whereas surface La³⁺ provides Lewis acidic binding sites to stabilize TEA adsorption and synergistically downshift the O 2p antibonding band. The combined effects strengthen TEA adsorption and improve sensor performance. This work demonstrates a viable single-atom dual-dopant approach to design high-sensitivity and selective gas sensors, offering insights into the atomic-scale tuning of semiconductor surfaces for chemical sensing applications.