Functionalization of Nanostructured Hematite Thin-Film Electrodes with the Light-Harvesting Membrane Protein C-Phycocyanin Yields an Enhanced Photocurrent

The integration of light-harvesting proteins and other photosynthetic molecular machinery with semiconductor surfaces plays an important role in improving their performance as solar-cell materials. Phycocyanin is one such protein that can be employed for this purpose. Phycocyanins have light-harvesting properties and belong to the phycobilisome protein family. They are present in cyanobacteria, which capture light energy and funnel it to reaction centers during photosynthesis. Here, a way of increasing the photocurrent of hematite by covalent cross-coupling with phycocyanin is reported. For this, a hematitephycocyanin integrated system is assembled by consecutive adsorption and cross-coupling of protein molecules, separated by an agarose layer and a linker molecule, on the top of a mesoporous hematite film. The hematitephycocyanin assembly shows a two-fold increased photocurrent in comparison with pristine hematite film. The increase in the photocurrent is attributed to the enhanced light absorption of the hematite film after integration with the protein, as is evident from the UVvis spectra and from the photocurrent-action spectrum. The assembly shows long-term stability and thus constitutes a promising hybrid photoanode for photo-electrochemical applications.