Facets and oxygen vacancies dual-engineering of CeO2-rGO nanocomposites for low-temperature NO2 detection: Experimental and DFT studies

Detecting trace levels of hazardous gas nitrogen dioxide (NO 2 ) at low temperatures still remains a persistent challenge. In this work, CeO 2 nanooctahedrons, nanorods and nanocubes with different exposed facets were synthesized and subsequently decorated with rGO. The NO 2 sensing properties of three CeO 2 nanocrystals-rGO nanocomposites at 65 ℃ were systematically investigated. CeO 2 nanocubes-rGO with (100) exposed plane showed superior sensing performance with eminent selectivity, long-term stability and low limit of detection (75 ppb). The results of characterizations and DFT calculations indicated the presence of abundant oxygen vacancies on (100) plane, due to the low formation energy of oxygen vacancy. Besides, the nature of polar plane and low adsorption energy on defective (100) plane promoted the adsorption of NO 2 on CeO 2 nanocubes-rGO nanocomposites. The decoration of rGO improved the electrical conductivity of CeO 2 , established the heterojunction and generated additional oxygen vacancies on the heterointerfaces. Therefore, the outstanding NO 2 sensing characters of CeO 2 nanocubes-rGO could be attributed to the polar exposed planes, abundant oxygen vacancies and plentiful interfacial heterojunctions. The present approach sheds light on the rational design of sensing materials via facet- and defect-engineering, and developed a CeO 2 -based NO 2 sensors with a low working temperature for environmental monitoring and safety assurance.