CeO2-induced defect-site engineering in CoxOy-SiO2 composites prepared by sol-gel combustion for photocatalytic degradation of organic dyes

Thanh C. Ly; Huy Q. Dang; Vinh Q. Dang; Thanh T. Lam; Quan A. Cao; Khoi D. Dang; Quan A. Nguyen; T. T. Van Pham; Hoang Phuoc Ho; Ha V. Le; Huy X. Le; Khoa D. Nguyen

doi:10.1016/j.ceramint.2026.04.317

CeO2-induced defect-site engineering in CoxOy-SiO2 composites prepared by sol-gel combustion for photocatalytic degradation of organic dyes
Journal article, 2026

Herein, we present a green and efficient one-pot sol-gel combustion approach to prepare cobalt-cerium oxide composites anchored on a silica matrix (CoxOy-CeO2-SiO2). The strategic incorporation of CeO2 into the silica framework could lead to the formation of defect sites, which enhance redox flexibility and promote the activation of CoxOy via a Fenton-like pathway, thereby improving its photocatalytic performance. Comprehensive characterization using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), N2 adsorption-desorption, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) confirmed the crystalline structure, porosity, and visible-light responsiveness. In addition, X-ray photoelectron spectroscopy (XPS) revealed the coexistence of Co2+/Co3+ and Ce3+/Ce4+ redox couples. The photocatalytic activity of the composites was systematically investigated via rhodamine B degradation, focusing on the effects of pH, catalyst dosage, H2O2 concentration, and inorganic anions. The degradation mechanism was elucidated by identifying key intermediate fragments using liquid chromatography-mass spectrometry (LC-MS). Radical-trapping experiments confirmed the crucial involvement of reactive oxygen species, including •OH, •O2−, and •OOH, in the degradation pathway of rhodamine B, while quenching experiments indicated that CeO2-induced defects promote h+/e− separation and radical formation. These findings highlight the synergistic role of CeO2-induced defects in enhancing photocatalytic efficiency. The composite exhibited excellent visible-light photocatalytic activity toward various organic dyes, achieving over 90% degradation efficiency for methyl violet, malachite green, indigo carmine, and amaranth, highlighting its great potential as a defect-engineered catalyst for solar-driven environmental remediation.

Defects

CoxOy-CeO2-SiO2

Fenton-like mechanism

Rhodamine B

Degradation