Polyethyleneimine/Polyethylene Glycol/Cerium Oxide Porous Core–Shell Structure for Room-Temperature Carbon Dioxide Gas Sensing

Hollow nanostructured materials possess a large specific surface area and excellent adsorptive properties, rendering them highly attractive for gas-sensing applications. In this work, a porous core-shell CeO2architecture was synthesized via a hydrothermal route and subsequently functionalized with polyethyleneimine/polyethylene glycol (PEI/PEG) to yield PEI/PEG/CeO2composites for room-temperature CO2detection. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface-area analyses confirmed the high specific surface area and the formation of the porous core-shell CeO2morphology, while SEM coupled with energy-dispersive X-ray spectroscopy (EDS) verified successful immobilization of PEI/PEG on the CeO2surface. Gas-sensing tests demonstrated that the PEI/PEG/CeO2sensor achieved a detection limit as low as 200 ppm CO2; at 1500 ppm CO2, the sensor exhibited a frequency shift of 86 Hz and rapid response/recovery times of 22 s and 70 s, respectively. Furthermore, the sensor showed high sensitivity,excellent repeatability and strong resistance to humidity. The outstanding CO2-sensing performance is attributed to the synergistic effects of the porous core-shell structure, the selective recognition afforded by the amine functional groups, and the formation of n-n heterojunctions at the CeO2-PEI interface. These findings provide deeper insight into the gas-sensing mechanisms and performance characteristics of PEI/PEG-functionalized CeO2composites.