Photocatalytic Hydrogen Production from Noncovalent Biohybrid Photosystem I/Pt Nanoparticle Complexes

A photocatalytic hydrogen-evolving system based on intermolecular electron transfer between native Photosystem I (PSI) and electrostatically associated Pt nanoparticles is reported. Using cytochrome c6 as the soluble mediator and ascorbate as the sacrificial electron donor, visible-light-induced H2 production occurs for PSI/Pt nanoparticle biohybrids at a rate of 244 μmol H2 (mg chlorophyll)−1 h−1 or 21 034 mol H2 (mole PSI)−1 h−1. These results demonstrate that highly efficient photocatalysis of H2 can be obtained for a self-assembled, noncovalent complex between PSI and Pt nanoparticles; a molecular wire between the terminal acceptor of PSI, the [4Fe−4S] cluster FB, and the nanoparticle is not required. EPR characterization of the electron-transfer reactions in PSI/Pt nanoparticle biohybrids shows blocked electron transfer to flavodoxin, the native acceptor protein of PSI, and presents evidence of low-temperature photogenerated electron transfer between PSI and the Pt nanoparticle. This work demonstrates a feasible strategy for linking molecular catalysts to PSI that takes advantage of electrostatic-directed assembly to mimic acceptor protein binding.