Sol–gel synthesis of LaCoO3 and La0.9CoO3 perovskites for photocatalytic degradation of methylene blue and neutral red dyes

Abstract

The main goal of this study is the development of non-precious, highly effective, stable photocatalysts for the degradation of organic dyes. In this work, we utilize a strategy to regulate the surface and structure of catalysts to boost the photocatalytic activity and stability through A-site deficiency of La_1-xCoO₃ perovskites. We fabricated a novel perovskite structure with a nominal composition of La_1-xCoO₃ (x = 0 and 0.1) using a facile sol–gel method. Comprehensive characterization of the fabricated samples was performed using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, and UV–Vis spectroscopy. XRD confirmed the formation of LaCoO₃ and La_0.9CoO₃ at 750 °C, both exhibiting a rhombohedral phase structure. FTIR analysis revealed characteristic bands at 585 cm⁻¹ and 520 cm⁻¹, corresponding to the M–O–M reflection mode and M–O stretching vibrations, respectively. SEM micrographs showed pseudo-spherical grains with varying sizes and porosities for both samples. BET analysis further demonstrated specific surface areas of 9.58 m²/g for LaCoO₃ and 11.24 m²/g for La_0.9CoO₃. Optical and photocatalytic investigations indicated that the two materials possess semiconductor properties, with LaCoO₃ and La_0.9CoO₃ exhibiting band gaps of 2.78 eV and 2.64 eV, respectively. Photocatalytic tests under visible light revealed significant degradation of the model dyes; LaCoO₃ achieved removal efficiencies of 56.41% for MB and 91.45% for NR, while La_0.9CoO₃ demonstrated superior performance, reaching 80.07% degradation of MB and 98.16% of NR. These findings underscore the enhanced catalytic efficiency of La_0.9CoO₃ compared to LaCoO₃, making it a promising candidate for the photodegradation of organic pollutants under visible-light irradiation.