Carbon-catalyzed dye-sensitization for solar hydrogen production

Abstract

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, 100mW/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.