Core-shell Bi2O3/CeO2 heterojunction for enhanced formaldehyde gas sensor

Bi 2 O 3 microspheres modified with CeO 2 were successfully synthesized via the hydrothermal method, and a gas sensor based on this composite material was prepared. Various analytical techniques were employed to examine the morphological and structural characteristics of the Bi 2 O 3 /CeO 2 composites. The synthesized Bi 2 O 3 microspheres exhibited a uniform size, with a particle diameter of approximately 2.5 μm. CeO 2 nanoparticles could be clearly observed on the surface of the Bi 2 O 3 microspheres. The results of X-ray photoelectron spectroscopy revealed that the adsorbed oxygen and oxygen vacancies on Bi 2 O 3 doped with CeO 2 increased, potentially due to the presence of Ce 3+ /Ce 4+ ions. The Bi 2 O 3 /CeO 2 sensors demonstrated significantly enhanced sensing properties for formaldehyde at room temperature. At a formaldehyde concentration of 100 ppm, the reactivity of the Bi 2 O 3 /CeO 2 sensor was 137 %, exhibiting a 6.6-fold enhancement compared to the Bi 2 O 3 sensor. Furthermore, the adsorption energy, differential charge density, and state density of the sample were calculated using density functional theory (DFT). Subsequently, the gas-sensing mechanism was analyzed and discussed. The results indicate that CeO 2 -modified Bi 2 O 3 nanospheres can enhance the adsorption energy of formaldehyde. The formation of a heterojunction facilitates electron transfer, thereby improving the gas-sensing properties. Furthermore, the gas sensing mechanism was discussed and analyzed using density functional theory (DFT) calculations.