“Sol-gel and hydrothermal synthesis of CeO2 NPs: Their physiochemical properties and applications for gas sensor with photocatalytic activities”

Cerium dioxide (CeO2) nanoparticles were synthesized through sol–gel and hydrothermal methods, yielding materials with distinct properties. Characterization techniques including Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV–Vis), X-ray Diffraction (XRD), Raman spectroscopy, Cyclic Voltammetry (CV), Photoluminescence spectra (PL), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy with Selected Area Electron Diffraction (TEM-SAED) were employed to analyse the synthesized nanoparticles. The FTIR analysis revealed an absorption band at 475 cm−1, while UV–Visible spectroscopy determined band gap energies of 3 eV and 3.16 eV for the sol–gel and hydrothermal methods, respectively. XRD analysis indicated crystalline sizes of 14.57 nm and 17.41 nm for the sol–gel and hydrothermal methods, respectively. Raman spectroscopy demonstrated active peaks at 464 cm−1 for the sol–gel method and 463 cm−1 for the hydrothermal method. Cyclic Voltammetry showcased different oxidation and reduction peaks, while Photoluminescence spectra provided insights into the excitation spectrum of CeO2 nanoparticles. FESEM and TEM-SAED images revealed nano-sized spherical spongy CeO2 nanoparticles. Furthermore, the synthesized CeO2 nanoparticles exhibited promising photocatalytic degradation activity against methyl blue (MB) dye under sunlight irradiation, with degradation efficiencies of 92 % and 82 % for the sol–gel and hydrothermal methods, respectively. Additionally, gas sensing properties for various gases (ethanol, methanol, CO2, LPG, H2S, and NH3) were evaluated using domestic gas sensor systems, showing potential applicability across a broad temperature range from 50 °C to 350 °C.