Thermocatalytic Performance of LaCo[sub.1−x]Ni[sub.x]O[sub.3−δ] Perovskites in the Degradation of Rhodamine B

• Published in: Catalysts Vol. 13; no. 2
• Main Authors: Christensen, Benjamin H, Deganello, Francesca, La Parola, Valeria, Jørgensen, Mads K, Boffa, Vittorio, Østergaard, Ma
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.02.2023
• Subjects: Crystals; Structure; Germany
• ISSN: 2073-4344; 2073-4344
• DOI: 10.3390/catal13020325

Perovskite-type LaCo[sub.1−x]Ni[sub.x]O[sub.3−δ] (x = 0, 0.2, 0.4, 0.6, and 0.8) powders were synthesized by solution combustion synthesis. The crystal structure, morphology, texture, and surface were characterized by X-ray powder diffraction combined with Rietveld refinement, scanning electron microscopy, N[sub.2]-adsorption, X-ray photoelectron spectroscopy, and zeta-potential analysis. The thermocatalytic properties of the perovskites were investigated by UV-Vis spectroscopy through degradation of rhodamine B in the temperature range 25-60 °C. For the first time, this perovskite system was proven to catalyze the degradation of a water pollutant, as the degradation of rhodamine B occurred within 60 min at 25 °C. It was found that undoped LaCoO[sub.3−δ] is the fastest to degrade rhodamine B, despite exhibiting the largest energy band gap (1.90 eV) and very small surface area (3.31 m[sup.2] g[sup.−1]). Among the Ni-doped samples, the catalytic performance is balanced between two main contrasting factors, the positive effect of the increase in the surface area (maximum of 12.87 m[sup.2] g[sup.−1] for 80 mol% Ni) and the negative effect of the Co(III) stabilization in the structure (78% in LaCoO[sub.3] and 89-90% in the Ni-containing ones). Thus, the Co(II)/Co(III) redox couple is the key parameter in the dark ambient degradation of rhodamine B using cobaltite perovskites.