Visible-light-driven Co–Al LDH/g-C3N5 nanoarchitecture for dual pollutant degradation and sustainable H2O2 production with photoluminescence detection capability

Abstract

The development of efficient and sustainable photocatalysts for environmental remediation is of significant interest in addressing the rising concerns of pharmaceutical and dye contaminants in aquatic systems. In this work, a Co–Al layered double hydroxide (Co–Al LDH) decorated on a nitrogen-enriched graphitic carbon nitride (g-C₃N₅) nanocomposite (LN) with varying weight ratios (1 : 2, 1 : 1, 2 : 1) was successfully synthesised via a facile solvothermal method followed by ultrasonic exfoliation. The optimised LN2 : 1 catalyst with enhanced photocatalytic behaviour was evaluated for photocatalytic organic pollutant degradation, oxygen reduction reaction (ORR) and antibiotic detection via photoluminescence sensing. The LN2 : 1 nanocomposite achieved the highest degradation efficiency of 93.4% against ciprofloxacin (CIP) and 92.1% against Cresol Red (CR) within 120 minutes under solar irradiation, demonstrating its superior catalytic activity compared to pristine g-C₃N₅ and Co–Al LDH. Furthermore, the composite demonstrated enhanced hydrogen peroxide (H₂O₂) generation of 1903.28 µM L⁻¹ (5.5 times that of g-C₃N₅ and 16.43 times that of Co–Al LDH), which was substantially higher than that of pristine components, indicating its ability to drive reactive oxygen species (ROS)-mediated photocatalytic pathways. Moreover, LN2 : 1 showed the most efficient photoluminescence sensing performance toward ciprofloxacin (CIP), achieving a limit of detection (LOD) of 0.982 ppm and R² of 0.979. The BET surface area analysis demonstrated a 2D nano-platelet-like composite with a higher surface area of 30.647 m² g⁻¹, indicative of a structure with abundant active sites for light harvesting and catalytic activation. Experimental analysis, including electrochemical analysis and radical scavenging tests, indicated the involvement of a Type-II mechanism, which markedly enhances charge carrier separation and utilisation, facilitating the generation of ROS such as superoxide (˙O₂⁻) and hydroxyl (˙OH) radicals that drive REDOX processes. This study provides a sustainable photocatalytic strategy with the potential to tackle real-world environmental challenges by enabling efficient degradation of emerging contaminants and advancing water purification technologies.