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

Abstract

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.

Decorating Thermodynamically Stable (101) Facets of TiO2 with MoO3 for Multifunctional Sustainable Hydrogen Energy and Ammonia Gas Sensing Applications

“…The gas sensing activity of TiO 2 and 4 TM heterostructure was found to be proportional to the operating temperature and the optimum activity was recorded at 250 °C as on increasing the temperature, the activation energy barrier of the surface reactions drastically subdued. , However, the gas sensing activity of the 4 TM heterostructure was found to be almost 2.5-fold higher than that of pristine TiO 2 , as illustrated in Figure c, which manifests the positive synergistic relationship between TiO 2 and MoO 3 . The recyclability plot of 4 TM at 250 °C is depicted in Figure d, which reveals the inconsiderable activity loss in successive cycles ascribed to the emergence of the activation energy barrier between the adsorbent gas sensor and adsorbed NH 3 gas. − …”

Exploring the Contribution of Intelligent Nanomaterials in Gas Sensing

“…The ′self‐heating′ method was developed to lessen this disadvantage of power use. This technique uses the sensing layer inside the analytical system as a heater [8,9] . One approach to tackle high energy consumption involves reducing the dimensions of the sensing element.…”

“…Semiconductor metal oxides are increasingly recognized as key gas‐sensing materials owing to their distinct, adjustable physical and chemical properties utilized in detecting harmful, toxic, pollutant, and explosive gases [9] . The inherent characteristics of metal oxides, including their composite forms, such as the porous structure offering a high specific surface area and modifiable band gaps with unique semiconductor traits, position them as compelling choices for gas sensing applications [10] .…”

“…Currently, various morphologies and structures of metal oxide semiconductors have been prepared using various methods, encompassing nanosheets, nanocubes, nanowires, nanorods, nanospheres, nanoplates, and nanoflowers [10–11] . Additionally, hollow nanostructures, with their unique traits like high surface areas, efficient interfacial charge transfer, high surface permeability, and reduced density, have exhibited substantial promise in gas sensor applications [8–11] …”

“…The subsequent section will delve into the categorisation of various types of gas sensors based on their sensing elements and detection characteristics. Notably, gas sensors operating at room temperature are favoured over their high‐temperature counterparts due to their lower power consumption and decreased risk of ignition, especially when detecting combustible or explosive analytes [8,9] . Figure 1 shows the diagrammatic representation of a sensor that generates an electrical response.…”