Opposite Sensing Response of Heterojunction Gas Sensors Based on SnO₂–Cr₂O₃ Nanocomposites to H₂ against CO and Its Selectivity Mechanism

Abstract

Metal oxide semiconductor (MOS) gas sensors show poor selectivity when exposed to mixed gases. This is a challenge in gas sensors and limits their wide applications. There is no efficient way to detect a specific gas when two homogeneous gases are concurrently exposed to sensing materials. The p–n nanojunction of xSnO2–yCr2O3 nanocomposites (NCs) are prepared and used as sensing materials (x/y shows the Sn/Cr molar ratio in the SnO2–Cr2O3 composite and is marked as Sn x Cr y for simplicity). The gas sensing properties, crystal structure, morphology, and chemical states are characterized by employing an electrochemical workstation, an X-ray diffractometer, a transmission electron microscope, and an X-ray photoelectron spectrometer, respectively. The gas sensing results indicate that Sn x Cr y NCs with x/y greater than 0.07 demonstrate a p-type behavior to both CO and H2, whereas the Sn x Cr y NCs with x/y < 0.07 illustrate an n-type behavior to the aforementioned reduced gases. Interestingly, the Sn x Cr y NCs with x/y = 0.07 show an n-type behavior to H2 but a p-type to CO. The effect of the operating temperature on the opposite sensing response of the fabricated sensors has been investigated. Most importantly, the mechanism of selectivity opposite sensing response is proposed using the aforementioned characterization techniques. This paper proposes a promising strategy to overcome the drawback of low selectivity of this type of sensor.

Conductivity and aging behavior of Sr(Ti0.6Fe0.4)1−xO3−δ mixed conductor materials

“…Iron-doped strontium titanate with B-site deciencies [Sr(Ti 0.6 Fe 0.4 ) 1−x O 3−d (with the 'x' values of 0.01, 0.02, and 0.03)] were synthesized by a sol-gel route from Sr(CH 3 COO) 2 -$2H 2 O (AR), Ti(CH 3 CH 2 CH 2 CH 2 O) 4 (AR), and Fe 2 O 3 (AR). [43][44][45][46][47] Here, strontium acetate interplayed with butyl titanate to develop the sol and concurrently Fe 2 O 3 dispersed homogeneously on the sol during moderate magnetic stirring. The product was obtained in the form of a powder via sol-drying at the temperature of 50 °C.…”

New Analysis Method for Adsorption in Gas (H2, CO)–Solid (SnO2) Systems Based on Gas Sensing

“…The gas concentration is presented in all figures. The test instrument and process can be seen in our previous work, as shown in Figure . The test system consists of two gas distribution devices, a test chamber, and an electrochemical workstation.…”

“…MOS-based materials have been extensively used for gas sensor application. − Their operating mechanism can be simply formulated as follows. Oxidizing gases such as O 2 adsorbed on the surface of SnO 2 can capture free electrons from its conductivity band, which increases the electrical conductivity.…”

Advances in Sno₂-Based Nanomaterials for Photocatalysis, Supercapacitors, and Antibacterial Activities

“…The increased effectiveness of its practical applications may be due to the improved properties, such as increased surface area, chemical and thermal stability, increased surface activities or number of active surface sites, enhanced charge transfer processes, mechanical strength, reduced electron-hole recombination, etc. [21][22][23][24][25][26][27][28][29][30].…”