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

CeO 2 and ZrO 2 nanospheres were successfully prepared by hydrothermal synthesis. From the as-synthesized pristine nanostructures, ZrO 2 –CeO 2 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% ZrO 2 –CeO 2 composite heterostructures, respectively, which were found to be smaller than that of pristine CeO 2 (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 m 2 /g for 2.5–10% ZrO 2 –CeO 2 nanocomposite heterostructures, respectively, as compared to the pure CeO 2 having 53.2 m 2 /g. 7.5% ZrO 2 -decorated CeO 2 nanocomposite heterostructure manifested remarkable enhancement in the sensing performance response of 1475 displayed as compared to the pure CeO 2 response of 205. The improved sensing performance of the 7.5% ZrO 2 –CeO 2 sensor is likely to have originated from the decrease in the band gap, enhanced surface area, the existence of large oxygen vacancies on the ZrO 2 surface, and the formation of ZrO 2 –CeO 2 heterojunctions in nanocomposites. Further, the enhanced gas sensing properties along with the sensing mechanism are discussed in detail.