Carbon-catalyzed dye-sensitization for solar hydrogen production

The catalytic effects of four different carbon materials (graphite, multi-walled carbon nanotubes, carbon fibers, and activated carbon) on dye-sensitized solar hydrogen production were investigated under a simulated solar light (AM 1.5G, 100 mW/cm²). Eosin-Y (EY) and triethanolamine (TEOA) were employed as a sensitizer and electron donor, respectively. All the tested carbon materials enhanced the sensitized H₂ production, while multi-walled carbon nanotubes (CNT) exhibited the highest catalytic activity with 9- and 4-fold enhanced H₂ production and photocurrent generation, respectively. This suggests that CNT is highly effective in catalyzing charge injection and thus sensitized H₂ production. With Pt loading onto the carbon materials, the H₂ production was further improved by a maximum of 10 times. With the bare carbon materials, EY underwent simultaneous spectral shifts and decreases in absorbance presumably due to stepwise de-bromination and cleavage of chromophoric groups. With CNT/Pt, however, only the former was observed despite far higher H₂ production. This indicates that the regeneration of EY is significantly enhanced with CNT/Pt. A detailed comparison of carbon materials and the sensitized mechanism was discussed.