Ultrasonic spray pyrolysis synthesis of three-dimensional ZnFe2O4-based macroporous spheres for excellent sensitive acetone gas sensor

The preparation process and gas sensitivity test of three-dimensional sphere spinel ferrites with well-assembled macroporous structures have been reported in this paper. The three-dimensional ZnFe2O4 macroporous spheres (3D ZnFe2O4 MPs) were prepared by one-step ultrasonic spray pyrolysis (USP), in which self-assembly sulfonated polystyrene (S-PS) spheres were employed as sacrificial template. The as-prepared samples possessed interconnected macroporous with pore diameters about 200 nm can be observed in TEM characterization, which provided more reactive active sites. The catalyst Pd was doped in 3D ZnFe2O4 MPs with the attempt of enhancing gas-sensing performance, which has been confirmed existed as Pd2+ formation by XRD and XPS analysis. In a comparison with pure 3D ZnFe2O4 MPs, the 0.5% PdO- dopded 3D ZnFe2O4 MPs exhibited a 2 times higher response (18.9) to 100 ppm acetone at 275 degrees C. Furthermore, the PdO-dopded 3D ZnFe2O4 MPs-based sensor also presented excellent selectivity and good long-term stability towards acetone. The outstanding sensing performance can be attributed to the 3D spheres with interconnect macroporous structure, electronic sensitization and catalytic effects of PdO. The relative sensing mechanism has been discussed in detail.