Fabrication of metal-organic frameworks derived Co3O4 loaded on TiO2: Influence of Fe loading on the Co3O4/TiO2 heterostructure for low-ppm benzene detection

We report the low-concentration detection of benzene using a metal–organic framework (MOF) derived Co3O4/TiO2 heterostructures loaded with 0.5–2 wt.% Fe synthesized using the co-precipitation method. The intrinsic properties of the heterostructures, such as their surface crystal structures, adsorption states, and chemical states, were examined. The sensing properties of the sensors were tested for nine (9) gases, including benzene, toluene, ethylbenzene (BTE), ethanol, acetone, carbon monoxide (CO), methane (CH4), carbon dioxide (CO2), and nitrogen dioxide (NO2) at various temperatures. The 1.0 wt.% Fe/Co3O4/TiO2 heterostructure-based sensor disclosed higher responses of ∼ 3 toward 2 ppm benzene at 175 °C. Furthermore, the sensor was able to experimentally detect benzene as low as 0.35 ppm and exhibited a low theoretical limit of detection (∼4.17 ppb) toward benzene at 175 °C, which increased at higher temperatures. The sensors were very stable in dry air and 20 % RH for 25 days. We infer that the excellent benzene detection could be associated with the loading of Fe3+ on the surface of the Co3O4/TiO2, which increased the specific surface area, narrowed the band gap, and provided numerous oxygen vacancies. Finally, the sensing mechanism linked with the loading of Fe3+ on the surface of Co3O4/TiO2 is discussed in detail.