Mechanism of enhancing the formaldehyde sensing properties of Co3O4via Ag modification

Abstract

Hollow Co₃O₄ hierarchical microspheres assembled from many compact nanowires have been successfully synthesized via a facile hydrothermal method from the precursor Co(CO₃)_0.5(OH)·0.11H₂O followed by annealing treatment. The product has a well-defined morphology, is porous, and has a larger surface area as seen through various analytical characterizations; thus, it can act as a good basis for further modification to improve its gas-sensing properties. The sensing tests indicate that the Ag@Co₃O₄ composite formed via Ag modification can not only improve the sensing response to formaldehyde by several times that of pure Co₃O₄, but also reduce the optimum operating temperature of the sensor. Furthermore, the gas-sensing mechanism is also discussed in detail, including the effect of Ag addition on the electronic transfer of the Ag@Co₃O₄ composite. There are still many challenges in making a formaldehyde sensor with high sensitivity using the cheaper noble metal Ag as modified reagent via a facile synthesis and doping method.