Constructing S-Scheme Charge Migration in a Self-Assembled In2O3/WO3 Heterojunction for Photothermal-Driven Dual-Gas Detection

Abstract

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.