Composition-Dependent Structural, Optical, and Photocatalytic Properties of Silver-Decorated Cobalt Ferrite/Graphitic Carbon Nitride Heterostructures for Enhanced Phenol Degradation

Efficient regulation of interfacial charge transfer through composition tuning is crucial for developing high-performance visible-light photocatalysts. In this study, the weight ratio of Ag–CoFe2O4 to g-C3N4 was systematically tuned (100:0, 75:25, 50:50, and 25:75 wt.%) to elucidate composition-dependent optical and interfacial properties and optimize photocatalytic degradation of phenol. The resulting heterostructures consisted of Ag-containing CoFe2O4 nanoparticles intimately integrated with two-dimensional g-C3N4, generating well-defined interfaces for charge-carrier migration. Among the investigated compositions, the 50:50 wt.% Ag–CoFe2O4/g-C3N4 heterostructure exhibited the highest photocatalytic activity, achieving approximately 60% phenol removal within 10 min, >90% within 20 min, and nearly 100% within 30 min. Further optimization revealed an optimum catalyst dosage of 10 mg, which achieved complete phenol removal within approximately 15 min, while 15% H2O2 accelerated complete removal to approximately 10 min. The superior performance of the optimized 50:50 wt.% composition is attributed to a favorable balance between visible-light harvesting, heterointerfacial contact, accessible reactive sites, and efficient charge separation and migration, together with Ag-mediated plasmonic effects and Co/Fe-mediated H2O2 activation for reactive oxygen species generation. The optimized heterostructure also demonstrated good recyclability, retaining approximately 97% phenol removal in the later cycles. These findings demonstrate that tuning the Ag–CoFe2O4:g-C3N4 weight ratio provides an effective strategy for engineering interfacial charge transfer and maximizing photocatalytic performance for industrial wastewater treatment.