ZrO2/CeO2-Heterostructured Nanocomposites for Enhanced Carbon Monoxide Gas Sensing

CeO2 and ZrO2 nanospheres were successfully prepared by hydrothermal synthesis. From the as-synthesized pristine nanostructures, ZrO2–CeO2 nanocomposite heterostructures with different weight percent ratios of 2.5, 5, 7.5, and 10% were prepared mechanically. The morphology and structural characteristics of the as-synthesized metal oxides and nanocomposites were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy studies. The UV–visible diffuse reflectance spectroscopic technique revealed band gaps of 2.95, 2.96, 2.91, and 2.83 eV of the 2.5–10% ZrO2–CeO2 composite heterostructures, respectively, which were found to be smaller than that of pristine CeO2 (3.03 eV). Furthermore, the Brunauer–Emmett–Teller surface area studies revealed enhanced surface areas of 81.5, 67.6, 74.8, and 58.4 m2/g for 2.5–10% ZrO2–CeO2 nanocomposite heterostructures, respectively, as compared to the pure CeO2 having 53.2 m2/g. 7.5% ZrO2-decorated CeO2 nanocomposite heterostructure manifested remarkable enhancement in the sensing performance response of 1475 displayed as compared to the pure CeO2 response of 205. The improved sensing performance of the 7.5% ZrO2–CeO2 sensor is likely to have originated from the decrease in the band gap, enhanced surface area, the existence of large oxygen vacancies on the ZrO2 surface, and the formation of ZrO2–CeO2 heterojunctions in nanocomposites. Further, the enhanced gas sensing properties along with the sensing mechanism are discussed in detail.