PdO modified hollow In₂O₃ nanospheres for CO detection in humidity environment

Pure In 2 O 3 and In 2 O 3 loaded with 1 mol%, 2 mol%, and 3 mol% PdO (PdIn-1, PdIn-2, PdIn-3) were successfully synthesized via simple hydrothermal and reduction methods. The characterization results revealed that the hollow nanosphere morphology of In 2 O 3 was not destroyed after the introduction of PdO. The PdIn-2 exhibited bigger specific surface area (45.16 m 2 /g) than that of pure In 2 O 3 (32.91 m 2 /g). The CO sensing results showed that PdIn-2 lowered the optimal operating temperature of the sensor (from 280°C to 240°C) and reduced the response recovery time (from 10s/110s to 6s/109s for 500 ppm CO) compared to pure In 2 O 3 sensor. At the optimum operating temperature, the PdIn-2 sensor achieves a response of 4.15 for 100 ppm CO, which is 3.7 times the response of pure In 2 O 3 . Additionally, PdIn-2 maintained good CO detection capability even at higher relative humidity levels (89%RH). Besides, the PdIn-2 sensor also has better selectivity and long-term stability for CO. The improvement of gas-sensitized performance is mainly attributed to the chemical sensitization and electron sensitization effects of PdO. This study indicates that PdO-modified In 2 O 3 hollow nanospheres are promising materials for sensitive CO gas detection with low humidity interference.