Biogenic Novel Z-scheme Ag–CeO2/MgAl-LDH composite for enhanced photocatalytic dye degradation

Abstract

The increasing demand for effective water treatment solutions to combat dye pollution has driven the advancement of sophisticated photocatalytic materials. In this study, a visible-light responsive novel Z-scheme heterojunction nanocomposite of silver-doped cerium oxide (Ag–CeO₂) nanoparticles supported on magnesium aluminum layered double hydroxide (MgAl-LDH) nanoclay, prepared by utilizing soap nut extract mediated sol-gel and hydrothermal treatment. Various analytical techniques were employed to assess the composite's physicochemical properties. The FT-IR and XRD spectra displayed intense peaks, confirming high crystallinity and purity, having an average crystallite size of 9.67 nm. Photoluminescence (PL) spectra suggested lower recombination rates in the novel composite. Morphology Analysis (SEM and TEM) revealed irregular spherical and granular CeO₂ and Ag integration on the layered hexagonal MgAl-LDH, showing a polycrystalline SAED pattern. X-ray photoelectron spectroscopy (XPS) indicated higher oxygen vacancies with exceptional redox potential for efficient degradation. Dynamic light scattering (DLS) showed polydisperse aggregated particles ranging from 100 to 250 nm with a highly stable zeta potential of −19.11 mV. Electrochemical impedance spectroscopy (EIS) shows increased impedance after Ag incorporation into CeO₂/MgAl-LDH indicating improved charge separation and reduced electron-hole recombination. The ternary composite exhibited 95 % efficiency in degrading Indigo Carmine dye at a 20 mg catalyst dosage for 5 ppm dye within 30 min at neutral pH. Ag doping significantly reduced the band gap to 0.9 eV, enhancing the visible-light absorption, and promoting the hydroxyl radical generation. 72 % dye mineralization was determined by Total organic carbon (TOC) analysis and 75 % efficiency was retained after reusing the catalyst for 5 cycles. Pseudo-first-order kinetics shows a linear regression coefficient (R² = 0.98). Therefore, our ternary composite guarantees an efficient and sustainable approach to water treatment.