Single-atom Ce targeted regulation SnS/SnS₂ heterojunction for sensitive and stable room-temperature ppb-level gas sensor

Metal sulfide-based gas sensors have the advantage of high sensitivity at room temperature, enabling high integration and low power consumption. However, a trade-off between low baseline resistance and good long-term stability at room temperature still needs to be addressed. Therefore, a single-atom Ce-targeted regulation strategy for p-SnS/n-SnS₂ was proposed. By doping different amounts of Ce, the amount and size of SnS quantum dots on the surface of SnS₂ can be regulated. Furthermore, Sn-S-Ce bonds are formed by combining single-atom Ce with SnS, which effectively hinders the growth and oxidation of SnS quantum dots, as evidenced by STEM, XPS, DFT, FTIR and EAXFS methods. Due to the unique energy band structure of p-SnS and n-SnS₂, Ce-doped SnS quantum dots serve as electronic sensitizers, effectively increasing the carrier concentration in SnS₂. The optimal gas sensor based on the 1% Ce-doped SnS/SnS₂ composites enables high sensitivity (with a response of 22.1 to 1 ppm NO₂), ultralow detection limit (1 ppb), excellent long-term stability at room temperature, and a lower baseline resistance. This engineering strategy of metal sulfide semiconductor heterostructures through single-atom targeted regulation provides new insights for further optimizing the composite system.