Cerium-Modified TiO₂ Nanomaterials Derived From Upcycled Coffee Ground Waste for Photocatalytic Oxidation and...

The valorization of spent coffee ground wastes to prepare advanced materials offers a promising pathway toward sustainable materials engineering. In this work, spent coffee grounds were valorized by their utilization as a template for the synthesis of Ce-loaded TiO₂ to be used as photocatalysts. The synthesis in the presence of the bio-derived sacrificial template in the absence of solvent promote a hierarchical porosity and surface area and an intimate contact between Ce and Ti precursors to improve the photocatalytic activity of the obtained composite material. Pure TiO₂ is made up of nanoparticles that organize into fairly uniform spherical agglomerates of ca. 1 μm. When Ce is introduced, this ordered structure gradually changes giving rise to less regular larger aggregates, and at higher loadings (5% Ce) the spherical morphology is no longer observed. In all cases a mesoporous structure is present. The activity of the obtained solids as photocatalysts was tested in three different reactions: (i) the photo reforming of ethanol in aqueous suspension of the photocatalysts in the absence of oxygen, to obtain hydrogen; (ii) the 2-propanol oxidation in gas-solid regime, and (iii) the 5‑hydroxymethylfurfural (5‑HMF) oxidation in aqueous suspension of the solids.