Enhanced NO 2 sensing performance based on Au nanocluster functionalized Co 3 O 4 nanospheres

P-type spinel cobalt oxide (Co 3 O 4 ) is widely used in the design and manufacture of chemical-resistant gas sensors due to its large specific surface area and high oxygen content. However, most current p-type Co 3 O 4 -based sensors exhibit weaknesses in gas susceptibility and high working temperature towards NO 2 detection. In this work, we report a highly sensitive NO 2 gas sensor based on Au-functionalized Co 3 O 4 nanospheres. The Co 3 O 4 nanospheres were fabricated by a hydrothermal method and then acted as a precursor for loading Au nanoclusters using glutathione (GSH) as a reducing reagent to obtain the composite material. The characterization results demonstrate that the introduction of Au doping significantly improved the chemical bonding state and microstructure of the composite material's surface. Compared to a pure Co 3 O 4 sensor, the Au/Co 3 O 4 nanohybrid with a weight percentage of 0.25% exhibited the highest response of 23.6 towards 20 ppm NO 2 at 120 °C. Further investigation indicates that it also has good humidity resistance, preferable repeatablity and adequate linearity. The gas sensing performance can be predominantly attributed to the spherical structure of the composite materials, modulation of the nano-Schottky junction, and the special chemical properties of Au nanoclusters.