Facet-Controlled Synthesis of CeO2 Nanoparticles for High-Performance CeO2 Nanoparticle/SnO2 Nanosheet Hybrid Gas Sensors

CeO₂ nanocubes with metastable {100} facets and CeO₂ nanooctahedrons with the most stable {111} facets are herein fabricated by controlling the morphology and facets of CeO₂ nanoparticles. SnO₂ nanosheet-based assembled films coated with these CeO₂ nanocubes or CeO₂ nanooctahedrons yield {100} CeO₂ nanocubes/SnO₂ nanosheets and {111} CeO₂ nanooctahedron/SnO₂ nanosheet hybrid gas sensors, respectively. The hybrid sensors with CeO₂ nanoparticles exhibited enhanced sensing responses to numerous chemical species relative to a pristine SnO₂ nanosheet gas sensor, including acetone, hydrogen, ethanol, ammonia, acetaldehyde, and allyl mercaptan. In particular, the responses of {100} CeO₂ nanocubes/SnO₂ nanosheets and {111} CeO₂ nanooctahedron/SnO₂ nanosheet gas sensors to acetone or allyl mercaptan were 6.8 and 10.3 times higher, respectively, than that of the pristine SnO₂ nanosheet gas sensor. Furthermore, the sensor response to ammonia was 2.5 times higher than that of a commercial volatile organic compound (VOC) gas sensor (TGS2602, Figaro Engineering Inc.). The CeO₂ nanocube-based sensor with exposed metastable {100} facets promotes the adsorption and oxidation of VOCs owing to the higher surface energy of the metastable {100} facets and therefore exhibits a higher sensing performance than the CeO₂ nanooctahedron-based sensor with an exposed {111} facet. The developed sensors show excellent potential for the detection of gas markers in human breath and perspiration for disease diagnosis.