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

[Display omitted] •Synthesis of CeO2 nanoparticles (CeO2 NPs) successfully synthesized by sol–gel and hydrothermal methods. It is cost effective and valuable approach.•CeO2 NPs exhibiting superior gas sensitivity and enhanced dye degradation.•CeO2 NPs exhibiting high NH3 gas sensing responses with other tested gases and photocatalytic activity under MB degraded under sunlight.•CeO2 NPs are often exhibit enhanced surface area leading to improve gas sensing and photocatalytic activity performance.•The gas sensing and photocatalytic activity of CeO2 NPs offers a wide range of applications with potential benefits for environmental sustainability, public health. 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.