Band gap engineering of Ag/CeO₂/Co₃O₄@biochar composite with superior light harvesting for photocatalytic removal of Diclofenac and Naphthalene from effluents

The development of effective photocatalytic materials for environmental uses is a burgeoning research domain nowadays. This study highlights the photodegradation of Diclofenac and Naphthalene facilitated by direct sunlight using Ag/CeO₂/Co₃O₄@BC (biochar) catalyst. A co-precipitation procedure was utilized to synthesize metal oxides, while a reduction process was implemented to dope silver nanoparticles. The properties of the synthesized Ag/CeO₂/Co₃O₄@BC catalyst were analyzed using various techniques including Scanning Electron Microscopy, X-ray Diffraction, Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy, Photoluminescence, Ultraviolet–Visible Diffuse Reflectance Spectroscopy, Brunauer–Emmett–Teller and Energy-Dispersive X-ray to examine the structure of the crystal, surface morphological characteristics, optical properties, functional group, and elemental valency. The energy band gap of the nanocomposite, as determined from Tauc's graphs, was around 2.7 eV. The experimental analysis indicates that Ag/CeO₂/Co₃O₄@BC has exceptional photodegradation efficacy, with 92.86 ± 1.18% and 97.21 ± 1.21% degradation rates within 42 and 30 min for Diclofenac and Naphthalene, respectively. Different factors like reaction scenarios, the identification of reacting species, the mechanism involved, the impact of competing species, and the total organic carbon were studied and addressed. Liquid Chromatography–Mass Spectroscopy was employed to investigate intermediate products in the degradation route. Ag/CeO₂/Co₃O₄@BC has shown commendable stability and reusability after five successive deterioration cycles. The incorporation of biochar and Ag into the CeO₂–Co₃O₄ composite resulted in a significant reduction in charge recombination rates, as they functioned as an electron reservoir, leading to a marked improvement in the photocatalytic effectiveness of the nanocomposite. The Ag/CeO₂/Co₃O₄@BC composite serves as a promising material for the elimination of diverse pollutants in the foreseeable future.