Electrospun In2O3–WO3–Pd heterojunction nanofibers for ultralow-concentration NO2 detection at low-temperature

We report on the design and fabrication of electrospun one-dimensional In2O3-WO3-Pd heterojunction nano-fibers (NFs) and their outstanding NO2 sensing performance at low operating temperatures. Comprehensive morphological, structural and compositional analyses (FESEM, XRD, HRTEM, EDX, XPS) confirmed the successful synthesis of uniform, heteronanofibers with well-defined interfaces. The optimized sensor, based on In2O3-WO3 (90:10) decorated with 0.01 wt% Pd, exhibited an exceptional response of 441.3 to 1 ppm NO2 at 150 degrees C and 30% RH, corresponding to 19-and 25-fold enhancements over pristine In2O3-WO3 and pure In2O3, respectively. Remarkably, the limit of detection reached 73 ppt, ranking among the best reported to date. The improved performance is attributed to the synergistic effects of In2O3-WO3 heterojunctions, which facilitate charge transfer, and the Pd catalytic sites, which promote NO2 adsorption and reaction kinetics. In addition to ultrahigh response and selectivity, the sensors demonstrated rapid response/recovery dynamics, excellent humidity tolerance, and long-term stability. These results highlight the potential of electrospun In2O3-WO3-Pd nanofibers as highly reliable platforms for next-generation NO2 sensors operating at low temperature with ultralow detection limits.