Interfacial optimization of CeO₂ nanoparticles loaded two-dimensional graphite carbon nitride toward synergistic enhancement of visible-light-driven photoelectric and photocatalytic hydrogen evolution

A novel series of CeO₂ nanoparticles (CeNP) loaded two-dimensional (2D) graphite carbon nitride nanosheet (CeNP/g-C₃N₄) composites which possess heterojunction are prepared with different proportions of CeNP by a reliable and straightforward method. The samples were employed to degrade the rhodamine B (RhB) and produce hydrogen. The microstructure, morphology, composition and surface chemical states of the samples are analyzed, and the ability of the photoelectric response is characterized. The characterization ensures uniform loading of CeNP over the g-C₃N₄ surface and a co-existence of Ce³⁺/Ce⁴⁺ in the CeNP/g-C₃N₄ composite. The FT-IR spectra have revealed the changes in the local dipole moment of amino groups, vibration mode of the constituent functional group and electronegativity, indicating the electric interaction between CeNP and g-C₃N₄. The photocatalytic hydrogen evolution efficiency of the CeNP/g-C₃N₄ increased initially and then decreased with the increasing of loaded CeNP. The CeNP/g–C₃N₄–C with 20 mg of CeNP was found to be the optimum proportion, which exhibited outstanding separation efficiency of the photo-generated carriers. The electron spin-resonance (ESR) spectra exhibit that the production of superoxide free radicals (∙O₂⁻) was much higher than that of hydroxyl free radicals (∙OH) indicating that ∙O₂⁻ species play a predominant role in the photocatalytic action. The mechanism for enhanced photocatalytic activity of the CeNP/g-C₃N₄ is attributed to the interfacial optimization, which improved the photo-generated carrier separation.