Photocatalytic hydrogen evolution without an electron mediator using a porphyrin–pyrene conjugate functionalized Pt nanocomposite as a photocatalyst

A new system for photoinduced hydrogen production has been constructed using a porphyrin–pyrene conjugate functionalized Pt nanocomposite as a photocatalyst and ethylenediaminetetraacetic acid (EDTA) as a sacrificial reductant in the absence of an electron mediator. Detailed spectral, computational and photochemical studies reveal that a photoinduced energy transfer from the photoexcited state of pyrene to the porphyrin occurs, accompanied by an electron transfer from the excited porphyrin moiety to the platinum catalyst for the H2 generation. Efficient photocatalytic hydrogen evolution from the system demonstrates the possibility of constructing a photocatalytic system that uses a Pt nanocomposite functionalized by self-assembled donor–acceptor conjugates as a photocatalyst. The turnover numbers (TONPt and TONdye) and quantum yields of hydrogen (ΦH2ΦH2) for the photoinduced hydrogen production system are 63, 6311, and 2.65%, respectively, and are calculated on the basis that the total amount of H2 evolved after 12 h of irradiation.

By using hydrogen bonding motif involving 5,10,15,20-tetrakis(4-(hydroxyl)phenyl)porphyrin and pyrenesulfonic acid, a conjugate with broader range of light absorption and efficient energy transfer from the pyrene to the porphyrin moiety has been constructed. It is found that the photocatalytic system that uses the conjugate functionalized Pt nanocomposite as a photocatalyst and EDTA as a sacrificial reductant is efficient for hydrogen evolution without an electron mediator.Figure optionsDownload as PowerPoint slide