Polar Cubic CeO₂ Nanoparticles on Graphene for Enhanced Room-Temperature NO₂ Sensing Performance

Composites of graphene and CeO2 nanoparticles with high-energy {100} facets exposed are prepared by the hydrothermal method. The percentage of high-energy {100} polar plane increases with elevating temperature, but the proportion of Ce3+ and oxygen vacancy (Ov) decreases. As a result, the sensitivity of CeO2{100}/graphene composites toward NO2 at room temperature is enhanced. First-principles calculations are done to uncover the mechanism. The adsorption energy of NO2 on the six-coordinated Ce of the CeO2{100} polar plane is the most negative, indicating the most preferred sites for the adsorption of NO2. However, if more Ov are generated, the proportion of six-coordinated Ce atoms will be reduced, and the interaction with NO2 will be reduced because of charge recombination. Consequently, the sensing performances toward NO2 are deteriorated. The results provide new information pertaining to the design and fabrication of room-temperature sensing materials for NO2.