Nonreducible, basic La2O3 to reducible, acidic La2-xSbxO3 with significant oxygen storage capacity, lower band gap, and effect on the catalytic activity

This paper describes one-pot solution combustion synthesis of La<inf>2-x</inf>Sb<inf>x</inf>O<inf>3</inf> (0.02 ≤ x ≤ 0.10). Detailed characterization using Xray diffraction (XRD) and X-ray photoelecron spectroscopy (XPS) is carried out to understand the doping effect and the oxidation state of antimony. Further, temperature-programmed desorption (TPD) with CO<inf>2</inf> is performed for evaluating the basic property and temperature-programmed reduction (TPR) with H<inf>2</inf> has been employed to obtain the oxygen storage capacity. The comparative study of La<inf>2</inf>O<inf>3</inf>, La<inf>2-x</inf>Sb<inf>x</inf>O<inf>3</inf> (0.02 ≤ x ≤ 0.10) shows that as the concentration of Sb increases, the basicity decreases and the oxygen storage capacity increases. Thus, nonreducible and basic La<inf>2</inf>O<inf>3</inf> can be transformed to significantly reducible and acidic La<inf>2-x</inf>Sb<inf>x</inf>O<inf>3</inf> (0.02 ≤ x ≤ 0.10). Further, solid state UV spectroscopy shows that due to the antimony doping, band gap of La<inf>2</inf>O<inf>3</inf> decreases significantly. Moreover, antimony doping also modifies the support property of La<inf>2</inf>O<inf>3</inf> as demonstrated in the catalytic CO<inf>2</inf> methanation reaction in the presence of hydrogen. Ru-doped La<inf>2</inf>O<inf>3</inf> and La<inf>1.96</inf>Sb<inf>0.04</inf>O<inf>3</inf> shows different selectivity toward methane formation and the later favors the reverse water gas shift reaction.