Selective corrosion of LaCoO3 by NaOH: structural evolution and enhanced activity for benzene oxidation

Abstract

La(OH)₃ nanosheets have been successfully coated on electrospun LaCoO₃ nanorods using a simple and facile corrosion process, where La cations are selectively precipitated using NaOH. During the oxidation process, La(OH)₃ is converted to La₂O₃ having a mutual effect with the spontaneously generated Co₃O₄ and the predominant LaCoO₃ component. The performances for catalytic benzene oxidation and characterization results indicate that the alkaline treatment of electrospun LaCoO₃ can improve the apparent catalytic activity because more surface adsorbed oxygen species and exposed Co³⁺ are generated. However, if the treatment time reaches 9 h, over-deposition of La(OH)₃/La₂O₃ species on the surface may cause a large fraction of active Co species to be inaccessible, resulting in a lower specific activity (2.9 × 10⁻⁶ mol_C6H6 m⁻² h⁻¹) compared to that of untreated LaCoO₃ (4.8 × 10⁻⁶ mol_C6H6 m⁻² h⁻¹). A treatment time of 3 h provides the highest specific activity, 1.01 × 10⁻⁵ mol_C6H6 m⁻² h⁻¹. Moreover, the obtained catalyst shows deactivation of only 3% benzene conversion in a stability test at 450 °C for 48 h. Therefore, NaOH-treated LaCoO₃ is a promising catalyst for the practical removal of volatile organic compounds due to its high efficiency, good stability, and convenient preparation.