Bandgap-engineered Fe-doped LaCoO3 perovskites for solar-driven photocatalytic degradation of crystal violet

Perovskite oxide photocatalysts exhibit significant potential for solar-driven wastewater remediation; however, their moderate band gaps and rapid charge recombination limit their practical efficiency. In this study, Fe-doped lanthanum cobaltite perovskites (LaCo1-xFexO3; x = 0.05 and 0.07, denoted as LCFO-5 and LCFO-7) were synthesized via a citrate-assisted sol-gel auto-combustion method and evaluated for the photocatalytic degradation of crystal violet (CV), a persistent and genotoxic triphenylmethane dye, under simulated solar irradiation. Rietveld-refined X-ray diffraction (XRD) analysis confirmed a single-phase rhombohedral structure (R-3c) without detectable secondary phases, indicating successful substitutional incorporation of Fe3+ at Co3+ sites. UV-Vis diffuse reflectance spectroscopy revealed progressive band gap narrowing from 2.1 eV (pristine LCO) to 1.9 eV (LCFO-5) and 1.7 eV (LCFO-7). Despite the lower band gap of LCFO-7, LCFO-5 exhibited superior photocatalytic performance, highlighting the importance of an optimal balance between light absorption and charge carrier recombination. FESEM and BET analyses indicated a mesoporous structure with a surface area of 64.27 m2 g-1 and an average pore diameter of ~ 3.83 nm, facilitating enhanced adsorption and catalytic activity. Under optimized conditions (40 ppm CV, 60 mg catalyst, pH 9, 80 min irradiation), LCFO-5 achieved 96.7% degradation efficiency, outperforming LCFO-7 and pristine LCO, following pseudo-first-order kinetics (k = 0.025 min-1). Radical scavenging experiments confirmed that hydroxyl (•OH) and superoxide (•O2-) radicals are the dominant reactive species. The superior performance of LCFO-5 is attributed to the optimal balance between Fe-induced active sites and minimal structural disorder. Additionally, LCFO-5 demonstrated excellent stability over multiple reuse cycles. These findings establish that controlled Fe doping in LaCoO3 effectively enhances band structure, charge separation, and surface reactivity, offering a cost-effective and scalable strategy for the photocatalytic removal of organic pollutants from wastewater.