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.