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The porous Pd-loaded In₂O₃ hollow spheres were successfully prepared by simple one-step method with the template of carbon spheres. The effect of calcination temperatures on morphology, composition and gas sensing performance of the as-obtained products was discussed by a series of test methods. The sample calcined at 550^∘C showed uniform porous hollow spheres with an average diameter of 100nm. Gas-sensing results exhibited that the Pd-In₂O₃ hollow spheres-based sensor possessed excellent sensing properties to formaldehyde, which include high response value (33), low working temperature (180^∘C) and fast response and recovery time (12s and 22s). The enhanced HCHO-sensing properties of Pd-In₂O₃ composites were attributed to the special porous and hollow structure, abundant oxygen vacancies and the catalysis of palladium. Pd-loaded In₂O₃ hollow spheres had been proved to be an ideal material for detecting HCHO at a low working temperature.

In this work, the azo dye Congo red (CR) was degraded by a Fe–In₂O₃ catalyst under the irradiation of ultrasonic. The Fe–In₂O₃ catalyst was prepared by a fast and moderate solvothermal method followed by the characterization of X-ray diffraction and scanning electron microscope. The effects of operating parameters, such as catalyst composition, catalyst dosage, initial dye concentration, ultrasonic power and ultrasonic frequency on degradation process were discussed. In the experiment, the optimum CR removal of 97.75% in 60min was achieved under the conditions, i.e., catalyst dosage of 0.06$\mathrm{\text{g}}\cdot L^{-1}$, CR concentration of 10$\mathrm{\text{mg}}\cdot {\mathrm{\text{L}}}^{-1}$, ultrasonic frequency of 45kHz and ultrasonic power of 100W. Besides, the CR degradation behavior by the catalyst with ultrasonic is well in accordance with the first-order kinetic model.