Electronic Structure and Room Temperature Ferromagnetism in Gd‐doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting

Enhanced visible light photocatalytic activity of Gd-doped CeO₂ nanoparticles (NPs) is experimentally demonstrated, whereas there are very few reports on this mechanism with rare earth doping. All-pure and Gd-doped CeO₂ NPs are synthesized using a coprecipitation method and characterized using X-ray diffraction (XRD), absorption spectroscopy, surface-enhanced Raman Spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID). The effect of Gd-doping on properties of CeO₂ is discussed along with defects and oxygen vacancies generation. The XRD confirms the incorporation of Gd³⁺ at the Ce³⁺/Ce⁴⁺ site by keeping the crystal structure same. The average particle size from transmission electron microscopy (TEM) images is in the range of 5-7 nm. The XPS spectra of Ce 3d, O 1s, and Gd 4d exhibits the formation of oxygen vacancies to maintain the charge neutrality when Ce⁴⁺ changes to Ce³⁺. The gradual increase in hydrogen production is observed with increasing Gd concentration. The observed results are in good correlation with the characterization results and a mechanism of water splitting is proposed on the basis of analyses. The absorption spectra reveal optical band gap (2.5-2.7 eV) of samples, showing band gap narrowing leads to desired optical absorbance and photoactivity of NPs.