Highly efficient visible/near-IR-light-driven photocatalytic H2 production over asymmetric phthalocyanine-sensitized TiO2

Abstract

Although dye-sensitized semiconductors for photocatalytic H₂ production have been reported for more than 20 years, the spectral response is still focused on the region of 400–600 nm and it is almost never extended to >600 nm. The present work successfully uses zinc phthalocyanine (Zn-tri-PcNc) and naphthalocyanine (Zn-tetra-Nc) to sensitize TiO₂ for photocatalytic H₂ production, which expands the spectral response of dye-sensitized semiconductors by harvesting light from 600 to 800 nm. Zn-tri-PcNc/TiO₂ has a H₂ production amount of 567.4 μmol with a turnover number (TON) of ∼7565, which is much higher than that of Zn-tetra-Nc/TiO₂ (236.5 μmol H₂ with a TON of ∼3153). In particular, Zn-tri-PcNc-sensitized TiO₂ shows an apparent quantum yield (AQY) of up to 0.2% under 700 nm monochromatic light irradiation and ∼0.1% under monochromatic light irradiation between 500 and 800 nm, indicating its efficient visible/near-IR-light-driven photocatalytic H₂ production. Future work on the panchromatic responsive dye-sensitized semiconductor system can be carried out using phthalocyanines co-sensitized with other dyes to utilize the whole visible/near-IR light of sunlight.