Exploring neodymium-doped LaCoO3 perovskite nanoparticles for structural tuning and methyl orange photocatalytic performance

Abstract

The La_1-xNdxCoO₃ (x = 0.25, 0.50, and 0.75) nanoparticles were successfully synthesized as a residual mass of 55 wt% and thermally stable at 400 °C using the sol–gel auto-combustion method. The X-ray data confirm a rhombohedral perovskite crystal structure with particle sizes ranging from 10 to 30 nm. The field emission scanning microscopy displays a cubical shape with an average size of 18.80–31.47 nm, as evidenced by the Nd, La, Co, and O elements detected by energy-dispersive analysis, and X-photoelectron spectroscopy revealed the expected chemical state. High-resolution transmission confirmed the highly crystalline nature of nanoparticles. UV–Visible reveals the optical band gap range of 3.90–3.99 eV. The magnetic behavior demonstrates an increase in magnetic moment with Nd³⁺-induced spin-state interactions LS–HS in Co³⁺, enhancing Co³⁺–O–Co³⁺ ferromagnetic exchange. The FTIR spectrum exhibits characteristic bands in the 400–650 cm⁻¹ region, attributed to Co–O stretching ~580–620 cm⁻¹ and O–Co–O bending ~430–480 cm⁻¹ vibrations of CoO₆ octahedra, along with a broad band ~500–540 cm⁻¹ corresponding to La–O/Nd–O modes, confirming successful Nd³⁺ substitution at the La-site. The obtained band gap energies enabled enhanced photocatalytic degradation of methyl orange under sunlight, achieving efficient removal within 210 min. Photodegradation kinetics followed a pseudo-first-order model, confirming the high activity of the synthesized nanoparticles. Mechanistic studies identified superoxide (–O₂⁻) and hydroxyl (–OH) radicals as the primary reactive species. As a result, Nd³⁺ substitution evidently improved the photocatalytic performance of La_1-xNd_x CoO₃ toward methyl orange degradation.