LaFeO3 is a p-type semiconductor catalytic material of perovskite structure (ABO3). Its magnetic and photocatalytic properties have been widely investigated,but the gas sensing properties are seldom reported,especially for toxic and noxious gases of NO2 and CO. The nanocomposites of LaFeO3 and LaFe1-xMgxO3 (x = 0.02,0.04,0.06) were prepared by various methods of the wet chemical process and their exact composition,crystal structures,grain sizes,specific surfaces,morphology and the electronic interaction between components were characterized by EDX,XRD,BET,SEM and XPS analysis. The sensors based on these nanocomposites have been fabricated to examine the sensing responses to gases,and the results show that these sensors exhibited high response to both oxidizing gas (NO2) and reducing gas (CO),and the response was greatly enhanced by the surface modification of MgO. The additive method,amount of additives,and their effects on the LaFeO3 structure and gas response have been analyzed and discussed by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopic (XPS) analysis.
BAI ShouLi,SHI BingJie,MA LiJing,YANG PengCheng,LIU ZhiYong,LI DianQing & CHEN AiFan State Key Laboratory of Chemical Resource Engineering,College of Science,Beijing University of Chemical Technology,Beijing 100029,China
La-hexaaluminate catalyst for methane catalytic combustion was synthesized by a reverse microemulsion.Pseudo-ternary phase diagrams of a quaternary microemulsion system of sodium dodecyl sulfate(SDS),n-pentanol,n-octane,and water(or Al(NO3)3 solution) were presented.The effects of alcohol chain length,cosurfactant-to-surfactant ratio,and salt concentration on the formation and stability of the microemulsion system were studied.The phenomenon that the conductivity changed with water supported the phase behavior of the microemulsion system.La(Mnx/Fex)Al12-xO19-δ catalysts,applied in methane combustion and with high-temperature stability,were synthesized within the stable areas of the phase diagram of the microemulsion system,when SDS was chosen as surfactant,n-pentanol as cosurfactant,and n-octane as oil phase.The physical properties and structure of the catalysts were characterized by BET method,transmission electron microscope(TEM),and X-ray diffraction(XRD).A micro-fixed-bed reactor was used to measure the catalytic activity of hexaaluminates in methane combustion.The results show that the reverse microemulsions can be used to produce discrete La-hexaaluminate nanoparticles that display excellent methane combustion activity owing to their high surface area and high thermal stability.
