Constructing S-Scheme Charge Migration in a Self-Assembled In2O3/WO3 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 In2O3/WO3 multilevel heterojunction is assembled by utilizing the electrostatic interaction between the hydroxyl group of In(OH)3 and WS2. 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 WO3 has a defect-rich (002) exposed surface in the In2O3/WO3 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 (O2–, 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 WO3/In2O3 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.