Facilitated Visible-Light-Driven Peroxymonosulfate Activation by a Co–Fe Layered Double Hydroxide Derived p–n Heterostructure for Sulfadiazine Degradation: Affecting Parameters, Kinetics, and Mechanistic Insights

The utilization of multivalence ionic metal species generated through a peroxymonosulfate (PMS)-assisted photocatalytic system is a promising platform for the selective degradation of water contaminants. However, achieving an effective electron transport and enhanced separation efficiency for these metal species is a daunting challenge. Thus, our current study addresses this challenge by using a Co–Fe-based layered-double-hydroxide template to synthesize a Co3O4/FeCo2O4 p–n heterojunction composite via a simple monosynthetic route. The resultant composite is thoroughly validated through advanced characterization techniques that efficiently activate PMS for sulfadiazine (SDZ) degradation under visible light, achieving a remarkable degradation efficiency of up to 90%. This accomplishment is attributed to factors including intimate interfacial contact, excellent light harvesting, mesoporosity, and oxygen vacancies within the composite. The formation of a distinct p–n heterojunction following the S-scheme charge dynamic significantly enhances photogenerated carrier separation and reduces charge recombination. The research delves into comprehensive investigations including degradation studies, active species trapping experiments, parameter exploration, and in-depth liquid chromatography–mass spectrometry for analysis of the degradation byproducts and pathway. Induced oxygen vacancies, strategically placed active surface sites, and mesoporosity in the Co3O4/FeCo2O4 composite synergistically boosted the sluggish PMS activation, leading to enhanced SDZ degradation. This study introduces a new perspective by demonstrating the potential of a single-material, mixed-metal oxide-based p–n heterojunction photocatalytic system following the S-scheme charge-transfer route for SDZ degradation. The findings contribute toward emphasizing the importance of tailored composite materials in tackling persistent contaminants.