An efficient p-n type based (NiO/CeO2) hybrid composite photocatalyst and its performance for cationic dye degradation: Probable degradation pathways, optimization activities, and depth mechanism insights

Abstract

In this work, NiO, CeO₂, and NiO/CeO₂ nanoparticles were prepared by stepwise a simple co-precipitation method and subsequently hybridized with various ratios (1:1, 1:2, and 1:3) a facile mixing method. The prepared NiO/CeO₂ composite samples at diverse ratios were analyzed using various analytical techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV–visible diffuse reflectance spectroscopy (UV-DRS), Field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Raman spectroscopy. These methods were employed to investigate the chemical composition, morphological features, and optical characteristics of the composites, providing a comprehensive understanding of their properties and potential characteristics. The photocatalytic degradation of methylene blue (MB) was investigated by the prepared NiO/CeO₂ composite samples with changing parameters, such as pH, catalyst dose, initial dye concentration, and agitation time under UV and solar light irradiation. Kinetic investigations revealed that the photodegradation of MB followed a pseudo-first-order kinetic model. Amongst the tested catalysts NiO/CeO₂ (1:2) exhibited the highest photo-degradation of MB dye (97%) at pH around 10 in 60 min compared to 45% for neat NiO and 67% for pure CeO₂ respectively. Similarly, under natural solar conditions, it takes time but degrades 94% Of MB at 210 min. The radical detection test was carried out with trapping agents ethylene diamine tetra acetic acid (EDTA), isopropyl alcohol (IPA), and benzoquinone (BQ) to establish the vital role of hydroxyl radicals (OH•) in the photodegradation of dyes. Eventually, the high stability and recyclability of the NiO/CeO₂ (1:2) photocatalyst was confirmed after five consecutive runs. The mechanistic pathway of the dye degradation was explained by the scheme model based on p-n hetero-junction. Overall the study demonstrates the effectiveness of NiO/CeO₂ (1:2) heterojunctions in photocatalytic applications, for the removal of dye contaminants from wastewater using UV and visible light conditions.