Modulation of the Surface Catalytic Activity of Boron-Doped Cobalt Oxide with Crystalline/Amorphous Interfaces for High-Stability Acetone Detection

Enhancing the gas–solid interface interaction between sensing materials and O₂ is promising for the development of high-performance metal oxide-based chemiresistive gas sensors. Nevertheless, high-performance gas sensors have not been developed owing to the lack of a deep understanding of the sensing mechanism with regards to gas–solid interface interactions. In this study, boron-doped cobalt oxide (B–Co₃O₄) with crystalline/amorphous interfaces was synthesized for acetone detection. The crystalline/amorphous interfaces reduce the valence of Co species (64.2% Co²⁺) and endow sensing materials with rich oxygen vacancies. The improvement of gas–solid interactions by modulating the d-band center (increase from −3.34 eV to −2.67 eV) level was innovatively developed by the novel in situ construction of crystalline/amorphous interfaces through a low-temperature annealing strategy, subsequently leading to improved acetone-sensing performance. Theoretical calculations and energy band structure analysis revealed that the construction of crystalline/amorphous interfaces led to an upshift in the d-band center of Co₃O₄ from −3.34 eV to −2.67 eV, which enhanced the interaction between Co 3d and O 2p, thus accelerating the interaction of BCo-225 and O₂. Consequently, the BCo-225 sensor showed a high response (105.6–100 ppm acetone), a low limit of detection (20 ppb), excellent stability in 4 days (only 2.7% response fluctuation vs 46.2% changes for Co₃O₄-225), and good stability for 6 months (109.3 to100 ppm acetone). The present BCo-225 sensor outperforms acetone sensors based on metal oxides synthesized via high-temperature annealing and overcomes the poor stability of traditional amorphous sensing materials.