Constructing S-Scheme Charge Migration in a Self-Assembled In ₂ O ₃ /WO ₃ Heterojunction for Photothermal-Driven Dual-Gas Detection

Increased safe and environmental awareness in production processes necessitates an ever-growing demand for efficient detection of ethanol/n-butanol/diesel fuel blends (clean energy) in rapid, real time. However, the forces between multiplexed organic molecules in complex environments induce a decrease in the flash point, thus requiring sensors with high selectivity and low-temperature detection capabilities. In this study, an In 2 O 3 /WO 3 multilevel heterojunction is assembled by utilizing the electrostatic interaction between the hydroxyl group of In(OH) 3 and WS 2 . The material achieves dual detection of ethanol and n-butanol under the excitation of light and temperature fields. It also possesses fast response/recovery times, excellent selectivity, and good long-term stability. The WO 3 has a defect-rich (002) exposed surface in the In 2 O 3 /WO 3 heterojunction, and the special electronic structure of the heterojunction induces carrier migration at the S-scheme heterointerface under photothermal activation, which promotes the generation of more reactive oxygen species (O 2 –, O – ) from the sensing material. The special chemical reaction of the sensor between oxygen anions and the target gas at room temperature (RT) and 120 °C is the basis for the realization of dual-selective detection of ethanol and n-butanol. The sensing mechanism of the WO 3 /In 2 O 3 heterojunction for ethanol/n-butanol has been systematically investigated based on energy band structure analysis and in situ Raman spectroscopic characterization. This work focuses on the potential of metal oxide-based S-scheme heterojunctions for high-performance gas sensor applications.