The study of cerium oxide as a photocatalyst under visible light irradiation is an important research area in photochemistry and photocatalysis. T. Santhoshini Priya has conducted a thorough investigation of cerium oxide as a photocatalyst, focusing on its potential for water splitting and hydrogen production, as well as environmental remediation applications such as air and water purification. The research includes analysis of the photocatalytic activity of cerium oxide, examining its bandgap, electronic structure, surface chemistry, surface area, particle size, morphology, and crystal structure using various techniques including X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, UV-Vis spectroscopy, photoluminescence spectroscopy, electron paramagnetic resonance spectroscopy, and Fourier-transform infrared spectroscopy. Additionally, the author investigated the photoelectrochemical behavior of cerium oxide using techniques such as electrochemical impedance spectroscopy, charge carrier, photo-generated charge separation, photo-induced electron transfer, and redox potential analysis. The study also explores the catalytic performance, stability, durability, and recycling potential of cerium oxide as a photocatalyst. The synthesis methods used for the preparation of cerium oxide photocatalyst include nanotechnology, sol-gel method, hydrothermal synthesis, co-precipitation method, precipitation method, combustion synthesis, doping, surface modification, and ligand functionalization. Overall, this study provides valuable insights into the properties and potential applications of cerium oxide as a photocatalyst under visible light irradiation. The findings of this research could have significant implications for the development of efficient and sustainable energy conversion technologies and environmental remediation strategies.