Enhanced ethanol sensing performance for chlorine doped nanocrystalline LaFeO_(3-δ) powders by citric sol-gel method

摘要

LaFeO_(3-x)Cl_x (x = 0, 0.15, 0.3 and 0.6) powders were prepared by citric sol-gel method. On the whole, the introduction of chlorine dopant results in the increase of average crystallite size and grain size, the reduction of intrinsic resistance, and overall enhancement of ethanol sensing performance. The best gas response of 79.2-200 ppm ethanol at prime working temperature of 136 ℃ was achieved by the sensor with x=0.6, which exhibited superior ethanol sensing performance to other sensors with good stability, gas response, selectivity, short response and recovery time at prime working temperature. XRD and XPS results show that chlorine dopant mainly exists in the form of Fe-Cl bond in the lattice and on the surface, which are more favorable to form than the La-Cl bond either in the lattice or on the surface. ab initio calculations on the process of gas sensing to C_2H_5OH on FeO-terminated LaFeO_3 (010) surface were performed under the guidance of XPS result, which indicate that the substitution of oxygen by chlorine both at the surface adsorption site and in the lattice should be responsible for the enhanced ethanol sensing performance of the chlorine doped LaFeO_3.