Applied Catalysis A: General, Vol.580, 140-148, 2019
Reversible adsorption of oxygen as superoxide ion on cerium doped zirconium titanate
Zirconium titanate (ZrTiO4) modified via cerium ions insertion in the oxide lattice has been successfully prepared via Sol-Gel synthesis forming solid solutions in the molar range between 0 and 10%. Cerium ions are hosted both as Ce4+ and Ce3+ ions whose ratio depends on the treatment undergone by the solid, with trivalent cerium always abundantly present even in strong oxidative conditions. Surface exposed Ce3+ ions are capable to adsorb O-2 in the range of temperature between 273 K and 77 K, as superoxide anion (O-2(center dot-)), having side-on structure and characterized by complete surface-to-molecule electron transfer (about 98% of spin density on O-2 molecule). Surprisingly such abundant adsorption is pressure dependent and fully reversible opening the perspective of applications of this system in the field of oxygen separation from gas mixtures.
Keywords:EPR;XPS;ZrTiO4 cerium;Superoxide;Reversible adsorption