Enhanced Ethanol Sensing Performance of Au and Cl Comodified LaFeO₃ Nanoparticles

Au and Cl comodified LaFeO3 nanoparticles were prepared by a citric sol–gel method through the addition of HAuCl4 into precursor. As evidenced by XRD and TEM, the addition of HAuCl4 suppressed the growth of LaFeO3 crystallite but hardly influenced the average particle size. XPS indicated that chlorine existed in the forms of organics and chlorides, while Au existed in the form of Au0. The simultaneous existence of Au and Cl on the surface suppressed the adventitious carbon contamination, whereas it favored the formation of La carbonate and the adsorption of oxygen species which were both beneficial for the improvement of gas sensing performance. At the prime working temperature of 120 °C, the Au and Cl comodified LaFeO3 sensor with the addition of 1 wt % HAuCl4 exhibited the highest gas response (220.7) reported so far to 100 ppm ethanol. Ab initio calculations on the Fe–O terminated LaFeO3 (001) surface preadsorbed by O atom demonstrated that more charge transferred from the ethanol to the surface additionally adsorbed by Au and Cl, resulting in higher gas response as observed.