One-step approach for preparing ozone gas sensors based on hierarchical NiCo₂O₄ structures

Abstract

International audienceNanostructured semiconducting oxides have been used as resistive gas sensors of toxic and non-toxic gases, but little emphasis has been placed on ozone sensing. Here we present a new ozone gas sensor based on hierarchical NiCo2O4 cubic structures synthesized via a facile urea-assisted co-precipitation method and annealed at 450 degrees C, which showed a low detection level. Ozone detection was carried out through electrical measurements with an optimized performance at 200 degrees C, with fast response (similar to 32 s) and recovery (similar to 60 s) time with suitable concentration range (from 28 to 165 ppb) for technological applications. Furthermore, NiCO2O4 platelets are selective to ozone compared to other oxidizing and reducing gases. The low detection level can be attributed to the coexistence of 3D structures based on hexagonal platelet-like and porous flower-like shape, which were revealed by field emission scanning electron microscopy (FE-SEM). In summary, NiCo2O4 is promising for detection of sub-ppb levels of ozone gas

Yolk-shelled ZnCo2O4 microspheres: Surface properties and gas sensing application

“…Gas sensing devices were fabricated by ultrasonically dispersing the as-prepared ZnCo 2 O 4 powders (10 mg) in 1 mL isopropyl alcohol and the suspension was then drop-cast onto a SiO 2 /Si substrate containing 100 nm thick Pt electrodes separated by a distance of 50 m. Details of preparation of the interdigitated electrodes (IDEs) are given in [19]. After dropping the ZnCo 2 O 4 solution, the substrates were heated to 100 • C for 10 min to evaporate the solvent, followed by calcination at 350 • C for 2 h in an electric furnace in air to stabilize the sample before the gas sensing measurements.…”

“…There are exceptions though, including some n-type semiconductors, viz. ZnO [15], SnO 2 [16], WO 3 [17], ␣-AgWO 4 [18], NiCo 2 O 4 [19] and In 2 O 3 [20], especially the nanocrystalline In 2 O 3 films able to operate at room temperature and detect ozone levels down to 15 ppb [21]. Despite the high sensitivity of the latter n-type semiconductor sensors, issues have to be addressed to improve stability and decrease response and recovery times [22].…”

“…The resulting binary metal oxides (AB 2 O 4 ) may adopt shapes such as nano/microflowers, nanowires, nanoarrays, nanorods, and hollow microspheres [40]. Gas sensors with these binary oxides have been used for detection of carbon monoxide, Liquefied Petroleum Gas (LPG), chlorine, ethanol, formaldehyde [27,29,30,33,41] in addition to ozone with p-type hexagonal platelets [19].…”

One-pot synthesis of nickel-cobalt hydroxyfluorides nanowires with ultrahigh energy density for an asymmetric supercapacitor

“…Generally, transition metal hydroxides or oxides have been widely applied in gas sensor, solar cell, Li-ion batteries, as well as supercapacitor owing to their fast redox reaction between the multiple oxidation states [11][12][13][14][15][16]. Among various transition metal hydroxides or oxides, Co(OH) 2 and Ni(OH) 2 have received wide attention in asymmetric supercapacitors due to their layered structures and characteristic redox reaction [17,18].…”

Response of a Zn2TiO4 Gas Sensor to Propanol at Room Temperature

“…The highest sensitivity to 40 ppm LPG was recorded at 250 °C [18]. A NiCo 2 O 4 sensor was studied for detecting O 3 [19]; the sensor demonstrated the highest sensitivity at 200 °C. Table 1 presents a brief list of selective research studies on different metal oxide composite sensing materials developed to test selected gases.…”