Enhanced sensing properties of CoFe2O4 nanosheet and Sensing Reaction Molecule Mechanism of Polar CoFe2O4 {111} Surfaces

The sensitivity of nanostructures to gases can be improved by exposing their polar surfaces. In this project, a CoFe2O4 nanosheet with {111} polar surface was obtained by selective adsorption of -OH, -OHC2H5OH, and SO42-. By hydrogenating the polar surface of Fe-CoFe2O4 (111), the -OH, -OC2H5OH and SO42- groups were effectively removed, which greatly improved the gas sensing sensitivity of CoFe2O4 nanosheets. This innovative technique provides a feasible way to improve the gas sensing performance of nanosheets. The results show a significant increase in the number of coordination-unsaturated metal-iron atoms (Fe3c) on polar surfaces, which improves sensitivity. As a gas sensing centre, Fe3c can adsorb oxygen, generate free electrons and catalyse sensing reactions. A microscopic mechanism for gas sensing is thus proposed. These results suggest that coordinated unsaturated metal atoms on the surface of metal oxides are active sites for gas sensing and that this gas sensing mechanism is universal.