Mesoporous Boron Subphosphide: Intrinsic Electron Deficiency Enabling Selective Low-ppm of Chemiresistive CO Detection in Harsh Environments

Carbon monoxide (CO) is infamous for its hazardous effects, mainly because it displaces oxygen in the bloodstream. Its danger is amplified by its odorless and colorless nature, making it difficult to detect. Exposure to even low concentrations of CO (≤50 ppm) is considered harmful to human health. Common sources of CO, such as fossil fuel-powered vehicles and machinery, primarily operate under harsh high-temperature conditions. Currently, available low-ppm of CO sensors struggle in these environments typical of CO emitters, highlighting the urgent need for advanced sensors capable of reliable operation in such conditions. In this study, nanocrystalline mesoporous icosahedral boron subphosphide is synthesized via a solid-state technique and evaluated for its CO sensing capabilities. The material exhibits selective detection of low ppm of CO at temperatures exceeding 500 °C, demonstrating a significant sensing response of ∼4 toward 50 ppm of CO at 600 °C. Electronic and structural analyses attribute boron subphosphide's chemiresistive behavior to its electron-deficient nature, which is crucial for effective CO interaction. Additionally, the sensitivity of boron subphosphide to CO can be modulated under external magnetic fields, underscoring its potential for adaptable sensing applications. This work introduces boron subphosphide as a promising candidate for CO sensing in harsh conditions and provides fundamental insights into its sensing mechanism driven by intrinsic electron deficiency. The findings offer a pathway for the development of advanced sensors capable of reliably detecting low concentrations of CO in harsh environments where precise monitoring is critical to public health and safety.