Mechanochemically assisted synthesis and visible light photocatalytic properties of lanthanum nickel oxide nanoparticles

Perovskite-type lanthanum nickel oxide (lanthanum nickelate, LaNiO3) nanoparticles with high photocatalytic activity were synthesized via a mechanochemical route. A high-energy planetary ball mill was employed for mechanochemical preparation of an activated precursor of LaNiO3 via a solid-state reaction of LaCl3, NiCl2, and NaOH. The mechanochemical treatment was performed for 1 h at a revolution speed of the milling pot of 600 rpm. In comparison to an un-milled precursor, a simple mixture of La(OH)3, Ni(OH)2, and NaCl, the activated precursor demonstrated that the mechanochemical treatment contributes to the formation of LaNiO3 at low temperatures. This effect, in turn, leads to reduction of the optical band gap, i.e., enhancement of the visible light photocatalytic activity. Standard characterization techniques confirmed that crystalline round LaNiO3 nanoparticles with a median diameter of 46 nm, a surface area of 23 m2/g, and an optical band gap of 1.09 eV were obtained after calcination of the mechanochemically treated precursor at 873 K for 1 h. The visible-light-driven photocatalytic activity was evaluated based on the photodegradation of methyl orange in an aqueous solution. The LaNiO3 catalyst nanoparticles efficiently decomposed methyl orange under visible light irradiation; more than 99% of methyl orange was removed from the solution in 2 h, indicating that the LaNiO3 nanoparticles possess good photocatalytic properties.