X-RAY PHOTOELECTRON-SPECTROSCOPY, TEMPERATURE-PROGRAMMED DESORPTION AND TEMPERATURE-PROGRAMMED REDUCTION STUDY OF LANIO3 AND LA2NIO4+DELTA CATALYSTS FOR METHANOL OXIDATION

An X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD) and reduction (TPR) study of LaNiO3 and La2NiO4+delta perovskites has been carried out. The existence of at least two different forms of oxygen in these compounds is shown by both oxygen reactivity (TPD and TPR) and XPS characterisation. XP spectra have also revealed a surface enrichment in lanthanum and oxygen. TPR profiles have shown a reduction of LaNiO3 through the formation of La2Ni2O5 as an intermediate compound. Above 450-degrees-C, LaNiO3 and intergrowth nickelates (La2NiO4 and La2NiO4+delta) undergo a final reduction to metallic Ni and La2O3. Between 200 and 400-degrees-C all three compounds exhibit a high catalytic activity in the total catalytic oxidation of methanol.