A multi-functional novel Z-scheme ZnIn ₂ S ₄ /g-C ₃ N ₅ heterojunction catalyst for enhanced visible light active photocatalysis and antimicrobial action

Photocatalysis represents a sustainable approach for cleaner energy production, wastewater treatment, and antimicrobial disinfection. Creating effective photocatalysts that respond to visible light is crucial for tackling worldwide challenges related to energy and the environment. Here, for the first time, we have reported a facile solvothermal strategy for the <i>in situ</i> growth of ZnIn₂S₄ nanoflowers on g-C₃N₅ nanoflakes, where the latter were synthesized <i>via</i> thermal polymerization followed by ultrasonic exfoliation. The resulting ZnIn₂S₄/g-C₃N₅ (ZCN-10) composite demonstrated outstanding photocatalytic activity, achieving 88.4% degradation of ciprofloxacin within 90 minutes under solar irradiation and producing 3368 μM L^-1 of H₂O₂ under visible light. This enhanced performance when compared to pristine ZnIn₂S₄ and g-C₃N₅ is attributed to the formation of a direct Z-scheme heterojunction, which promotes efficient charge separation, broadens light absorption, and optimizes the band structure and morphology. The ZCN-10 catalyst maintained high photocatalytic efficiency over four consecutive cycles and also exhibited notable antimicrobial activity, producing a 17 mm inhibition zone against <i>B. subtilis</i> and 30 mm inhibition zone against <i>E. coli</i>. Comprehensive analytical characterization confirmed the successful synthesis and structural integrity of the nanocomposite. Mechanistic studies, including radical scavenging and band structure analysis, revealed that the direct Z-scheme configuration significantly enhances charge carrier separation and utilization, facilitating the generation of reactive species such as superoxide (˙O₂ ^-) and hydroxyl (˙OH) radicals, which drive advanced oxidation processes (AOPs). This work highlights a promising route for developing earth-abundant, eco-friendly photocatalysts for environmental remediation and sustainable energy applications.