Photosystem I – Based Systems for Photoelectrochemical Energy Conversion

Abstract

This dissertation investigates the incorporation of Photosystem I (PSI), a supramolecular protein complex that participates in the light reactions of photosynthesis, into electrochemical systems intended for the conversion of photonic energy into chemical energy and electricity. First, I describe the fabrication of nanoporous gold leaf electrode films and detail the process by which they are decorated with PSI complexes. I further explain how the feature size of the substrate must be tuned such that the pores may accommodate multiple PSI complexes in order to produce enhanced photocurrent with respect to a planar electrode. Second, I develop a kinetic model for the photocatalytic effect produced by a monolayer of PSI on a planar electrode. I solve the resulting system of partial differential equations numerically and use the simulation to extract kinetic parameters from experimental data. Third, I describe the construction of stand-alone PSI-based photoelectrochemical cells, demonstrate their light transduction capabilities, and show that the devices continue to produce photocurrent for at least 9 months after their fabrication. Fourth, I present a method to deposit multilayer films of PSI by vacuum-assisted assembly. I characterize the resulting films optically and electrochemically and show that photocurrent production increases with thickness of the films. Furthermore, I demonstrate the largest photocurrent responses of the films are produced in response to irradiation by light of wavelengths that correspond to peaks in the films’ absorbance spectra. Finally, I offer general perspectives conclusions about the results presented herein and outline future directions in which this project may progress.