Kinetic model of the photocatalytic effect of a Photosystem I monolayer on a planar electrode surface.

Photosystem I (PSI), a photoactive protein complex that participates in the light reactions of natural photosynthesis, can exhibit photocatalytic capabilities when incorporated to electrochemical systems. Here we present a simulation for the photoelectrochemical behavior of an electrode modified with a monolayer of Photosystem I complexes during photochronoamperometric experiments in which the electrode is exposed to periods of darkness and irradiation. A kinetic model is derived from conservation statements for the various oxidation states of the reaction centers of PSI complexes and electrochemical mediators within the system. The kinetic parameters that dictate the performance of the simulation are extracted from experimental data and the resulting simulation is capable of predicting the photochronoamperometric behavior of the system over a range of overpotentials. The model is used to investigate the various contributions to the photocurrent production of the system as well as the effects of the orientation of PSI complexes adsorbed to the electrode surface.