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.