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

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.