Oxygen-vacancy engineering and junction design in CeO2 nanomaterials for photocatalysis and antibacterial action: A review

Cerium oxide (CeO2) nanomaterials occupy a distinctive position in environmental catalysis and antimicrobial technologies because their fluorite lattice accommodates oxygen vacancies and facile Ce3+/Ce4+ redox cycling. This review synthesizes recent progress in “defect programming” and junction engineering to convert CeO2 into high-performance platforms for solar-driven pollutant degradation and antibacterial action.We analyze how vacancy ensembles, aliovalent doping, and facet control reshape band structure, extend optical response, and modulate adsorption/activation of O2 and H2O. Emphasis is placed on interfacial designs type-II heterojunctions, direct Z-/S-schemes, and Schottky contacts with metals and conductive carbons that preserve redox potentials while suppressing electron-hole recombination.Synthesis strategies (co-precipitation, hydro/solvothermal, sol–gel/Pechini, microwave/ultrasound, and green/biotemplated routes) are benchmarked for their ability to set vacancy “set-points” and achieve intimate, clean interfaces. We connect characterization toolkits (XPS/UPS, EPR, Raman, UV–Vis DRS, TRPL, EIS/IMPS) to mechanistic fingerprints of reactive oxygen species (•O2⁻, •OH, ¹O2) generation under realistic aqueous conditions. Device-level architectures (immobilized films, polymeric and magnetic frameworks) and reactor/photonic choices are shown to be as determinative as powder composition for durability, separability, and solar utilization.Persistent challenges include disentangling genuine semiconductor pathways from dye/matrix artifacts, stabilizing vacancies in ion-rich waters, and converging on field-relevant metrics beyond decolorization (e.g., TOC mineralization and product inventories). We outline priorities for operando-verified vacancy control, co-design of materials with optics/reactors, robust anchoring and regeneration protocols, and standardized benchmarking to translate CeO2-centered composites into scalable environmental remediation and antibacterial technologies.