Solar hydrogen production coupled with the degradation of a dye pollutant using TiO₂ modified with platinum and nafion

The simultaneous production of molecular hydrogen (H₂) and degradation of rhodamine B (RhB) was successfully achieved using TiO₂ modified with platinum and nafion (Pt/TiO₂/Nf) under visible light ( > 420 nm). Pt/TiO₂/Nf exhibited high activity for H₂ production in the presence of RhB and EDTA as a photosensitizer (also an organic dye pollutant) and an electron donor, respectively. However, the activity of TiO₂ modified with either platinum or nafion for H₂ production was negligible under the same experimental conditions. The negatively charged nafion layer enhances the adsorption of cationic RhB and pulls protons, a source of hydrogen, to the surface of TiO₂ through electrostatic attraction. On the other hand, platinum deposits on TiO₂ can act as an electron sink and a temporary electron reservoir for the reduction of protons. With the production of H₂, RhB was gradually degraded through N -deethylation, which was confirmed by the spectral blue shift of the maximum absorption wavelength ( m a x) from 556 to 499 nm (corresponding to the m a x of rhodamine 110). With Pt/TiO₂/Nf employed at [ RhB ] = 20 M (0.6 mol), approximately 70 mol of H₂ was produced and RhB and its intermediates were completely removed over a 12 h period. A detailed reaction mechanism was discussed.