Hydrothermal synthesis and characterization of CuO–CoO/TiO2 for photocatalytic degradation of methylene blue under visible light and catalytic reduction of P-nitrophenol

Abstract

CuO–CoO/TiO2 has been prepared using TiO2-P-25, Cu(acac)2/Co(acac)3 (sample 1) and Cu(NO3)2/Co (NO3)2 (sample 2) by hydrothermal method. DRS, CV, EDX, XRD, XPS, Raman, FE-SEM, and TEM have been used for structural, optical, and morphological analyses of the samples. The anatase phase formation of the samples has been identified by powder X-ray diffraction and Raman spectroscopy. Cu and Co metals were present as CuO and CoO in both samples, according to XPS and Raman spectroscopy data. UV–Vis–NIR reflectance and cyclic voltammetry analysis were used to determine the absorption nature of the samples. Through these techniques, the band gap values of samples 1 and 2 were determined as 2.0 and 2.5 eV, respectively. Nanotube/nanosheet and nanoparticle morphologies were shown by samples 1 and 2, respectively, based on transmission electron microscopy (TEM) results. The synthesized nanomaterials were applied in the degradation of methylene blue (MB) under visible light. The photocatalytic activity of the samples was studied in the presence and absence of H2O2. Degradation time was 4–40 min in the presence of 2 mg of the catalyst. In addition, the samples were used as catalysts in the reduction of P-nitrophenol (PNP) by NaBH4. UV–Vis spectroscopy was used to monitor the progress of the catalytic and photocatalytic degradation reactions. Furthermore, the catalyst samples were removed and recycled several times. The photocatalytic degradation reaction was carried out in the presence of various free radical scavengers and hydroxyl radical and hole were determined as the main active species for samples 1 and 2, respectively.