Porous CoFe2O4/WO3/Ag composite for high-performance triethylamine gas sensor

Spinel ferrites with a general formula of AFe 2 O 4 (A=Zn, Mn, Ni, or Co) have attracted considerable attention in chemiresistive gas sensors, given their superior chemical stability and good catalytic activity. However, the development of spinel ferrite-based gas sensors that simultaneously possess high selectivity and excellent humidity resistance has so far remained challenging. Herein, we successfully fabricated a novel CoFe 2 O 4 /WO 3 /Ag (CWA) composite by depositing the WO 3 nanosheets and Ag nanoparticles successively onto the porous CoFe 2 O 4 (CFO) nanosheets that were obtained through co-precipitation, calcination, and in-situ reduction methods. Due to the unique porous layered structures of the CFO nanosheets, the formation of p-n heterojunctions between the CFO and WO 3 nanosheets, and the catalytic effects of the Ag nanoparticles, the CWA composite-based gas sensor exhibited distinct selectivity (at least 4 times enhanced sensitivity), wide detection range (0.1∼500 ppm) reproducibility (RSD=1.3% in 5 independent batches), stability (maximum 4.4% fluctuation over 56 days), and humidity resistance (>60.7% response retention at 90% RH) towards triethylamine (TEA). Density functional theory (DFT) calculations further proved the intense TEA chemisorption on the Fe sites and the indispensable role of Ag in electron mobility modulation. In addition, a practical gas-sensing system was also developed to demonstrate its real-world implementation. This study provided a general strategy for constructing spinel ferrite-based gas sensors that could work in high-humidity environments.