WO₃ Nanosheets/FeCo₂O₄ Nanoparticles Heterostructures for Highly Sensitive and Selective Ammonia Sensors

The gas - sensitive properties of metal oxide nanocomposites mainly depend on their structure and composition. In this paper, a highly sensitive ammonia sensor based on FeCo
₂
O
₄
nanoparticles modified WO
₃
nanosheet nanocomposite is prepared. The structure and composition of the sensor material are characterized by the systematic spectral and structural characterization. The results show that FeCo
₂
O
₄
nanoparticles grow on the surface of WO
₃
nanosheet and the interfacial contact is close, which leads to the P-N heterojunction and the increase of the relative specific surface area. The gas sensitivity test results show that the WO
₃
/FeCo
₂
O
₄
gas sensor has the highest sensitivity to NH
₃
(33.5 at 100 ppm) at 300 °C, with the characteristics of satisfactory selectivity, short response/recovery time, high repeatability and long stability. Compared with the intrinsic properties of WO
₃
and FeCo
₂
O
₄
, the sensitivity of WO
₃
/FeCo
₂
O
₄
nanocomposites is improved by tens of times. These excellent properties are attributed to the P-N heterojunction between WO
₃
nanosheets and FeCo
₂
O
₄
nanoparticles, as well as the good catalytic activity of FeCo
₂
O
₄
, which make it become a practical gas sensitive material for ammonia detection.