Physico-chemical and catalytic properties of gamma-irradiated lanthanum nickelate (LaNiO<inf>3</inf>)

Electronspin resonance (ESR) studies of γ-irradiated LaNiO3 revealed the formation of chemisorbed superoxide ion (O2-) and F centers (electrons trapped in anion vacancies). X-ray photoelectron spectroscopy (XPS) showed that the γ-irradiation of LaNiO3 in the presence of moisture leads to the reduction of the transition metal (Ni3+ to Ni2+) which in turn facilitates the formation of O2- and surface carbonate species (CO32-). A qualitative molecular orbital model has been proposed for the chemisorption of O2- on the reduced transition metal centers (Ni2+). The hydrated electron generated by the radiolysis of moisture reduces the transition metal. Gamma-irradiated LaNiO3 shows enhanced catalytic activity for the decomposition of hydrogen peroxide (H2O2) and the increase in catalytic activity is attributed to the reduced metal content. The formation of chemisorbed oxygen decreases the electrical conductivity by trapping the charge carriers.