Enhanced Ammonia Sensing Performance Based on FeCo2O4/WO3/rGO Ternary Nanocomposites

Ammonia (NH3) is a hazardous gas with an irritating odor that poses severe risks even in small quantities. To this end, in this article, an NH3 sensor based on FeCo2O4/WO3/reduced graphene oxide (rGO) ternary composites was designed by taking advantage of the utility of rGO for the enhancement of gas-sensitive properties of semiconductor materials at low temperatures as well as the unique physicochemical properties of spinel-type metal oxides. The synthesized products were analyzed using multiple techniques to determine their morphology and elemental composition. The results indicate successful growth of FeCo2O4/WO3 nanocomposites on rGO film, forming heterojunctions. The gas sensitivity tests show that the minimum detection concentration of the FeCo2O4/WO3/rGO gas sensor is 500 ppb, and the response value to 100 ppm NH3 is 19.8, which is about five and eight times higher than the WO3 and FeCo2O4 gas sensors, respectively. More critically, the optimal working temperature of the gas sensing element modified with rGO is 220 °C, which is reduced to varying degrees compared to both single and binary gas sensing units. On the other hand, the FeCo2O4/WO3/rGO gas sensing element has the ability to quickly detect NH3 in the low concentration ranges, such as a response/recovery time of only 2 s/1 s for 1 ppm gas. The structure of the FeCo2O4/WO3/rGO ternary composites is responsible for the enhanced performance of the gas sensing element, resembling the formation of a p-n-p heterojunction structure.