Hydrogen Production over Natural Fibrous Clays: UV-C Photocatalytic Activity of Sepiolite and Palygorskite

Natural fibrous clays—sepiolite (SEP) and palygorskite (PLG)—were examined as low-cost photocatalysts for UV-C hydrogen generation from aqueous methanol. Native and 24 h pre-irradiated samples were analyzed by gas quantification, FTIR, SEM, AAS, and zeta-potential measurements, with TiO₂ P25 as a benchmark. UV-C treatment activated PLG by removing carbon residues and reorganizing surface –OH groups, improving channel accessibility and enhancing H₂ production to near-P25 levels. SEP responded oppositely: stronger hydroxylation and hydrogen bonding stabilized methanol-derived intermediates, temporarily suppressing activity despite preserved structural integrity. Overall, differences arise from distinct surface-chemistry pathways rather than lattice changes, highlighting fibrous silicates as robust, tunable photocatalysts whose performance depends primarily on surface cleanliness and hydration.