Organoceria nanostructured hybrid materials: a novel approach for band gap modulation in ceria

The development of efficient visible light photocatalysts based on ceria (CeO₂) requires precise control over both morphology and electronic band structure. Herein, a facile one-pot hydrothermal method is reported for the preparation of crystallographically well-defined ceria nanocubes featuring enhanced photocatalytic response under visible light irradiation. The proposed approach relies on the in situ structural incorporation of 1,10-phenanthroline during crystal growth. Unlike conventional doping or surface functionalisation strategies, this method yields organic-inorganic nanostructured hybrid materials where the organic moiety is effectively incorporated into the fluorite-type ceria lattice through the formation of Ce-N coordination bonds while preserving the cubic morphology enclosed by reactive {100} facets and simultaneously increasing the specific surface area. Diffuse reflectance UV-Vis spectroscopy and valence band XPS analyses reveal that this integration induces the appearance of N 2p intraband gap states associated with the Ce-N bonds, resulting in a significant narrowing of the optical band gap and extending the light absorption edge into the visible region. Consequently, these organoceria hybrids exhibit a remarkable synergistic enhancement in photocatalytic hydrogen production via ethanol photoreforming under simulated solar irradiation, with hydrogen evolution rates being 7.5 times higher than those of pristine ceria nanocubes. This work demonstrates the potential of organic ligand-assisted lattice engineering as a versatile approach for tailoring the optoelectronic properties of ceria, thus opening new avenues for sustainable solar-to-chemical energy conversion.