La/Fe bimetallic MOF-derived p-LaFeO3/n-CdS heterojunction: efficient photocatalytic degradation of organic contaminants and adsorption isotherms

Abstract

Designing efficient catalysts with strong redox characteristics and high visible light absorption is of particular interest in the field of photocatalysis. In this study, we synthesized an active and cost-effective photocatalyst by combining MOF-derived La/Fe bimetallic LaFeO₃ porous nanosheets with hydrothermally synthesized CdS nanorods. Several p-LaFeO₃/n-CdS photocatalysts with different concentrations (wt%) of LaFeO₃ were synthesized, and their physicochemical properties were characterized by standard analytical techniques such as UV-vis DRS, FTIR, XRD, BET, SEM, TEM, EDX and XPS. The photocatalytic degradation performance of the synthesized materials was evaluated using chromophoric dyes such as rhodamine B (RhB) and congo red (CR) and antibiotics such as tetracycline (TC) and oxytetracycline (OTC) under visible light irradiation in aqueous suspension. The as-synthesized 15 wt% p-LaFeO₃/n-CdS (15 LC) heterojunction photocatalyst exhibited remarkable photocatalytic degradation performance against RhB (96%, 30 min), CR (98%, 25 min), TC (80%, 100 min), and OTC (78.6%, 75 min). The reactive oxygen species such as O₂˙⁻, h⁺, and ˙OH were involved in the degradation process, which was monitored through scavenger tests. The heterojunction photocatalyst effectively suppressed photoinduced electron–hole pair recombination and facilitated interfacial charge transfer. Based on experimental data and projected energy band positions, a type II mechanism is proposed to elucidate the photocatalytic degradation of organic contaminants, emphasizing the redox capabilities and broad visible light absorption of the synthesized photocatalyst. The phototransformation of 4-nitrophenol to 4-aminophenol and adsorption isotherms were also done using the 15 LC heterojunction photocatalyst, whereas in the case of the adsorption isotherms the curve fitted the Langmuir isotherm model.