High response to formaldehyde gas and ppb-level detectability of nanoparticle Cr2O3/ porous cubic ZnSnO3 composites p-n heterojunction gas sensor

A series of chromium trioxide/zinc metastannate (Cr2O3/ZnSnO3) composites with different ratios were prepared via a simple two-step hydrothermal and high-temperature sintering method. The samples underwent characterization and analysis to assess their micromorphologies, elemental distributions, chemical compositions, and specific surface areas. Furthermore, gas sensing properties were evaluated through experiment. Results showed that the cubic ZnSnO3 block in Cr2O3/ZnSnO3 was in close contact with the surface of nanoparticulate Cr2O3 and the specific surface area increases. Its primary elements are Zn, Sn, Cr, and O. The 15 wt% Cr2O3/ZnSnO3 sensor exhibited an optimal operating temperature of 175 °C, 75 °C lower than that of pure ZnSnO3 (250 °C). The 15 wt% Cr2O3/ZnSnO3 sensor exhibited the best sensing performance for formaldehyde gases with a concentration of 50 ppm. It exhibited a response of 37.8 and could detect ppb-level concentrations of formaldehyde (limit of detection = 612 ppb). Additionally, Cr2O3/ZnSnO3 showed good selectivity for formaldehyde in the presence of six gases, that is, acetone, formaldehyde, methanol, ethanol, ammonia, and carbon monoxide. Cr2O3/ZnSnO3 exhibited good short-term repeatability and long-term stability. Because of the excellent performance of Cr2O3/ZnSnO3 composites, they have broad application prospects in formaldehyde gas detection.